ritonavir (Rx)

HIV Infection

Not typically used as sole protease inhibitor (PI), but as pharmacokinetic enhancer of other PIs

Indicated in combination with other antiretroviral agents for the treatment of HIV-infection

300 mg PO q12hr intially; increase by 100 mg q12hr to 600 mg PO q12hr over 5 days as tolerated

Use as booster with another protease inhibitor: 100-400 mg PO qDay or divided q12hr

Hepatic Impairment

Monitor therapy carefully with moderate and severe hepatic impairment

HIV Infection

Indicated in combination with other antiretroviral agents for the treatment of pediatric patients with HIV-1 infection

Not used as sole protease inhibitor (PI), but as pharmacokinetic enhancer of other PIs

Age <1 month: Safety and efficacy not established

Age ≥1 month: 250 mg/m² PO q12hr initially; increase by 50 mg/m² q2-3days to 350-400 mg/m² q12hr; not to exceed 600 mg q12hr  

Adolescents: 300 mg PO q12hr intially; increase by 100 mg q12hr to 600 mg PO q12hr over 5 days as tolerated

Oral solution

• Do not administer to neonates before postmenstrual age of 44 weeks
• Contains 43.2% alcohol and 26.57% propylene glycol; total amounts of alcohol and propylene glycol from all medicines that are to be given to pediatric patients aged 1-6 months should be taken into account in order to avoid toxicity from these excipients
• Measure dose with calibrated oral syringe

Oral powder

• Used only for dosing increments of 100 mg
• Should not be used for doses <100-mg or for incremental doses between 100-mg intervals (use oral solution for these doses)

Contraindicated (35)

• alfuzosin

  ritonavir will increase the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• amiodarone

  ritonavir will increase the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  amiodarone will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Contraindicated.
  
  ritonavir increases levels of amiodarone by decreasing metabolism. Contraindicated.

• cobicistat

  cobicistat will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• cobimetinib

  ritonavir will increase the level or effect of cobimetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Avoid coadministration with strong CYP3A4 inhibitors with (increases cobimetinib systemic exposure by 6.7-fold).

• conivaptan

  ritonavir will increase the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of conivaptan with strong CYP3A4 inhibitors is contraindicated.

• dihydroergotamine

  ritonavir will increase the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• dihydroergotamine intranasal

  ritonavir will increase the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• disulfiram

  disulfiram increases toxicity of ritonavir by aldehyde dehydrogenase inhibition. Contraindicated. Interaction only associated with oral solution, which contains 42% alcohol.

• elagolix

  ritonavir will increase the level or effect of elagolix by Other (see comment). Contraindicated. Concomitant use of elagolix and strong OATP1B1 inhibitors is contraindicated.

• eliglustat

  ritonavir will increase the level or effect of eliglustat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors are contraindicated with eliglustat poor or intermediate metabolizers; reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors
  
  ritonavir increases levels of eliglustat by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. If coadministered with strong or moderate CYP2D6 inhibitors, reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive and intermediate metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  ritonavir, elvitegravir/cobicistat/emtricitabine/tenofovir DF. Other (see comment). Contraindicated. Comment: Elvitegravir/cobicistat/emtricitabine/tenofovir is a complete regimen for HIV and should not be administered with other antiretrovirals.
  
  ritonavir will increase the level or effect of elvitegravir/cobicistat/emtricitabine/tenofovir DF by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• enzalutamide

  ritonavir will increase the level or effect of enzalutamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  enzalutamide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• ergoloid mesylates

  ritonavir will increase the level or effect of ergoloid mesylates by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• ergonovine

  ritonavir will increase the level or effect of ergonovine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• finerenone

  ritonavir will increase the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• flibanserin

  ritonavir will increase the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of flibanserin with moderate or strong CYP3A4 inhibitors is contraindicated. Severe hypotension or syncope can occur.

• irinotecan

  ritonavir will increase the level or effect of irinotecan by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

• irinotecan liposomal

  ritonavir will increase the level or effect of irinotecan liposomal by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

• ivabradine

  ritonavir will increase the level or effect of ivabradine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of ivabradine with strong CYP3A4 inhibitors is contraindicated.

• lomitapide

  ritonavir increases levels of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Increases lomitapide levels several folds.

• lonafarnib

  ritonavir will increase the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Lonafarnib is a sensitive CYP3A4 substrate. Coadministration with strong or moderate CYP3A4 inhibitors is contraindicated.

• lovastatin

  ritonavir will increase the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors increase systemic statin exposure and risk of myopathy, including rhabdomyolysis
  
  lovastatin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

• lurasidone

  ritonavir will increase the level or effect of lurasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of lurasidone and strong CYP3A4 inhibitors is contraindicated.

• mavacamten

  ritonavir will increase the level or effect of mavacamten by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors may increase mavacamten systemic exposure, resulting in heart failure due to systolic dysfunction.

• methylergonovine

  ritonavir will increase the level or effect of methylergonovine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• naloxegol

  ritonavir will increase the level or effect of naloxegol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of naloxegol with strong CYP3A4 inhibitors can significantly increase naloxegol systemic exposure which may precipitate opioid withdrawal symptoms

• pimozide

  ritonavir increases levels of pimozide by decreasing metabolism. Contraindicated. Risk of QT interval prolongation.

• regorafenib

  ritonavir, regorafenib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors increase regorafenib levels and decrease exposure of the active metabolites M-2 and M-5.

• salmeterol

  ritonavir increases levels of salmeterol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Potential for increased toxicity.

• simvastatin

  ritonavir will increase the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  simvastatin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Contraindicated.
  
  ritonavir increases toxicity of simvastatin by Other (see comment). Contraindicated. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• St John's Wort

  St John's Wort will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• tinidazole

  tinidazole increases toxicity of ritonavir by aldehyde dehydrogenase inhibition. Contraindicated. Interaction only associated with oral solution, which contains 42% alcohol.

• venetoclax

  ritonavir will increase the level or effect of venetoclax by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Use of strong CYP3A4 inhibitors is contraindicated with venetoclax during the initial ramp-up dosing phase. If a strong CYP3A inhibitor must be used after the ramp-up phase, reduce the venetoclax dose by at least 75%.

• voclosporin

  ritonavir will increase the level or effect of voclosporin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• voriconazole

  voriconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  ritonavir decreases levels of voriconazole by increasing metabolism. Contraindicated. Ritonavir 400 mg BID decreases voriconazole levels; lower ritonavir doses have unknown effect.

Serious - Use Alternative (160)

• abametapir

  abametapir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. For 2 weeks after abametapir application, avoid taking drugs that are CYP3A4 substrates. If not feasible, avoid use of abametapir.

• acalabrutinib

  ritonavir will increase the level or effect of acalabrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of acalabrutinib with strong CYP3A inhibitors. If a strong CYP3A inhibitor must be used short-term (eg, up to 7 days), temporarily interrupt treatment with acalabrutinib.

• ado-trastuzumab emtansine

  ritonavir increases levels of ado-trastuzumab emtansine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. DM1, the cytotoxic component, is metabolized mainly by CYP3A4; strong CYP3A4 inhibitors may increase DM1 exposure and toxicity.

• afatinib

  ritonavir increases levels of afatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Reduce afatinib daily dose by 10 mg if not tolerated when coadministered with P-gp inhibitors.

• apalutamide

  apalutamide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP3A4 inducer, with drugs that are CYP3A4 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered. Adjust dose according to prescribing information if needed.

• apixaban

  ritonavir will increase the level or effect of apixaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If taking apixaban dose >2.5 mg BID, decrease dose by 50% if coadministered with strong dual inhibitors of CYP3A4 and P-gp; if currently taking apixaban 2.5 mg PO BID, avoid coadministration with strong dual inhibitors of CYP3A4 and P-gp

• aprepitant

  ritonavir will increase the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• atorvastatin

  ritonavir increases toxicity of atorvastatin by Other (see comment). Avoid or Use Alternate Drug. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• avanafil

  ritonavir will increase the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. CYP3A4 inhibitors may reduce avanafil clearance increasing systemic exposure to avanafil; significantly increased levels may result in significant adverse events including severe hypotension, syncope, visual changes, and priapism. Coadministration with strong CYP3A4 is contraindicated.

• avapritinib

  ritonavir will increase the level or effect of avapritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of avapritinib with strong CYP3A4 inhibitors.

• avatrombopag

  ritonavir will increase the level or effect of avatrombopag by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• axitinib

  ritonavir increases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration with strong CYP3A4 inhibitors, reduce axitinib dose by 50%.

• bedaquiline

  ritonavir will increase the level or effect of bedaquiline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of bedaquiline with strong CYP3A4 inhibitors for >14 consecutive days, unless the benefit of treatment outweighs the risk

• bosentan

  bosentan will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. stop bosentan >36 hours prior to PI initiation and restart 10 days after PI initiation at 62.5 mg once daily or every other day.

• bosutinib

  ritonavir increases levels of bosutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inhibitors increases bosutinib plasma concentration ~5-fold.
  
  ritonavir increases levels of bosutinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• brigatinib

  ritonavir will increase the level or effect of brigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant use of a strong CYP3A inhibitor cannot be avoided, reduce the brigatinib once daily dose by about 50% (ie, from 180 mg to 90 mg, or from 90 mg to 60 mg). After discontinuation of a strong CYP3A inhibitor, resume the brigatinib dose that was tolerated prior to initiating the strong CYP3A inhibitor.

• bromocriptine

  ritonavir will increase the level or effect of bromocriptine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• cabergoline

  ritonavir increases levels of cabergoline by decreasing metabolism. Contraindicated.

• cabotegravir

  ritonavir, cabotegravir. Other (see comment). Avoid or Use Alternate Drug. Comment: Cabotegravir plus rilpivirine is a complete regimen. Coadministration with other antiretroviral medications for treating HIV-1 infection is not recommended.

• cabozantinib

  ritonavir will increase the level or effect of cabozantinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of cabozantinib with strong CYP3A4 inhibitors. If a strong CYP3A4 inhibitor is required, decrease cabozantinib dose by 40 mg/day (Cometriq) or by 20 mg/day (Cabometyx). Resume previous dose 2-3 days after strong CYP3A4 inhibitor discontinued.

• calcitriol

  ritonavir will increase the level or effect of calcitriol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• capmatinib

  ritonavir will increase the level or effect of capmatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• carbamazepine

  carbamazepine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• ceritinib

  ritonavir increases levels of ceritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid if possible; if concomitant use is unavoidable, reduce ceritinib dose by ~33%; after discontinuation of strong CYP3A inhibitor, resume at previous dose.

• chloramphenicol

  chloramphenicol will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• cimetidine

  cimetidine will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• clarithromycin

  clarithromycin will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• cobicistat

  ritonavir will increase the level or effect of cobicistat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• colchicine

  ritonavir will increase the level or effect of colchicine by Other (see comment). Avoid or Use Alternate Drug. Colchicine is a P-gp and CYP3A4 substrate. Avoid use with drugs that are both P-gp and strong CYP3A4 inhibitors. If coadministration is necessary, decrease colchicine dose or frequency as recommended in prescribing information. Use of any colchicine product in conjunction with strong CYP3A4 inhibitors is contraindicated in patients with renal or hepatic impairment.

• copanlisib

  ritonavir will increase the level or effect of copanlisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant use with strong CYP3A inhibitors cannot be avoided, reduce copanlisib dose to 45 mg.

• dabrafenib

  ritonavir increases levels of dabrafenib by decreasing metabolism. Avoid or Use Alternate Drug. Strong CYP2C8 inhibitors may increase dabrafenib levels.
  
  ritonavir increases levels of dabrafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  dabrafenib will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• dacomitinib

  dacomitinib will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid use with CYP2D6 substrates where minimal increases in concentration of the CYP2D6 substrate may lead to serious or life-threatening toxicities.

• daridorexant

  ritonavir will increase the level or effect of daridorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• darunavir

  ritonavir will increase the level or effect of darunavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• dasatinib

  ritonavir will increase the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. May require decreased dasatinib dose or adjustment of dosing interval. Both ritonavir and dasatinib are CYP3A4 inhibitor, however, ritonavir is a strong CYP3A4 inhibitor and more likely to increase dasatinib levels and increase risk for toxicity including prolonged QT interval.

• dronedarone

  ritonavir will increase the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  dronedarone will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• edoxaban

  ritonavir will increase the level or effect of edoxaban by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Dose adjustment may be required with strong P-gp inhibitors. DVT/PE treatment: Decrease dose to 30 mg PO once daily. NVAF: No dose reduction recommended

• elagolix

  ritonavir will increase the level or effect of elagolix by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• elbasvir/grazoprevir

  ritonavir will increase the level or effect of elbasvir/grazoprevir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• eletriptan

  ritonavir increases levels of eletriptan by decreasing metabolism. Contraindicated. Separate by 72 hours.

• eluxadoline

  ritonavir increases levels of eluxadoline by decreasing metabolism. Avoid or Use Alternate Drug. Decrease eluxadoline dose to 75 mg PO BID if coadministered with OATP1B1 inhibitors. .

• encorafenib

  ritonavir will increase the level or effect of encorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant use of a strong CYP3A4 inhibitor is unavoidable, reduce encorafenib dose to one-third of the dose (eg, reduce from 450 mg/day to 150 mg/day). After discontinuing the inhibitor for 3-5 elimination half-lives, resume previous encorafenib dose.

• entrectinib

  ritonavir will increase the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of strong CYP3A4 inhibitors with entrectinib, a CYP3A4 substrate. If coadministration unavoidable, reduce entrectinib dose to 100 mg/day for patients aged 12 y or older with BSA >1.50m2. Resume previous entrectinib dose after discontinuing strong CYP3A inhibitor for 3-5 elimination half-lives.

• erdafitinib

  ritonavir will increase the level or effect of erdafitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration with strong CYP3A4 inhibitors, monitor closely for adverse reactions and consider decreasing dose accordingly. If strong CYP3A4 inhibitor is discontinued, consider increasing erdafitinib dose in the absence of any drug-related toxicities.
  
  erdafitinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If coadministration unavoidable, separate administration by at least 6 hr before or after administration of P-gp substrates with narrow therapeutic index.

• ergoloid mesylates

  ritonavir increases levels of ergoloid mesylates by decreasing metabolism. Contraindicated.

• ergotamine

  ritonavir will increase the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  ritonavir increases levels of ergotamine by decreasing metabolism. Contraindicated.

• erythromycin base

  erythromycin base will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• erythromycin ethylsuccinate

  erythromycin ethylsuccinate will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• erythromycin lactobionate

  erythromycin lactobionate will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• erythromycin stearate

  erythromycin stearate will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• ethinylestradiol

  ritonavir, ethinylestradiol. Other (see comment). Avoid or Use Alternate Drug. Comment: Significant changes (increase or decrease) can occur in estrogen plasma levels. Efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended. .
  
  ritonavir will increase the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• etravirine

  ritonavir, etravirine. Other (see comment). Contraindicated. Comment: Different preparations of ritonavir have varying effects on etravirine, due to alterations in metabolism. The following preparations are contraindicated with etravirine: ritonavir 600 mg bid; tipranavir/ritonavir; fosamprenavir/ritonavir; atazanavir/ritonavir. The following preparation should be co-admin. with caution: lopinavir/ritonavir. The following preparations need no dose adjustment: darunavir/ritonavir; saquinavir/ritonavir.
  
  etravirine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• everolimus

  ritonavir will increase the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  ritonavir will increase the level or effect of everolimus by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

• fedratinib

  ritonavir will increase the level or effect of fedratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid fedratinib coadministration with strong CYP3A4 inhibitors, decrease fedratinib dose to 200 mg/day. If CYP3A4 inhibitor discontinued, increase fedratinib dose to 300 mg/day for 2 weeks, and then 400 mg/day thereafter as tolerated.
  
  ritonavir will increase the level or effect of fedratinib by Other (see comment). Avoid or Use Alternate Drug. Avoid coadministration of fedratinib (a CYP3A4 and CYP2C19 substrate) with dual CYP3A4 and CYP2C19 inhibitor. Effect of coadministration of a dual CYP3A4 and CYP2C19 inhibitor with fedratinib has not been studied.

• felbamate

  ritonavir will increase the level or effect of felbamate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• fentanyl

  ritonavir will increase the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fentanyl intranasal

  ritonavir will increase the level or effect of fentanyl intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fentanyl transdermal

  ritonavir will increase the level or effect of fentanyl transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fentanyl transmucosal

  ritonavir will increase the level or effect of fentanyl transmucosal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fexinidazole

  ritonavir will decrease the level or effect of fexinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration, monitor fexinidazole for decreased efficacy owing to decreased plasma concentrations of active M1 and M2 metabolites.
  
  fexinidazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Fexinidazole inhibits CYP3A4. Coadministration may increase risk for adverse effects of CYP3A4 substrates.

• flecainide

  ritonavir will increase the level or effect of flecainide by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. Concurrent use of flecainide and ritonavir is contraindicated.
  
  ritonavir increases levels of flecainide by decreasing metabolism. Contraindicated.

• fluticasone intranasal

  ritonavir will increase the level or effect of fluticasone intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inhibitors may increase systemic corticosteroid adverse effects; monitor for signs/symptoms of high corticosteroid concentrations including Cushing type signs/symptoms.

• fosamprenavir

  ritonavir will increase the level or effect of fosamprenavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• gilteritinib

  ritonavir will increase the level or effect of gilteritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Consider alternatives to any strong CYP3A4 inhibitor when coadministered with gilteritinib. If such a combination cannot be avoided, closely monitor for gilteritinib-related adverse effects. Interrupt and reduce gilteritinib dosage in patients with serious or life-threatening toxicity.

• givosiran

  givosiran will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP2D6 substrates with givosiran. If unavoidable, decrease the CYP2D6 substrate dosage in accordance with approved product labeling.

• glasdegib

  ritonavir will increase the level or effect of glasdegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Consider alternate therapies that are not strong CYP3A inhibitors or monitor for increased risk of adverse effects, including QTc interval prolongation.

• glecaprevir/pibrentasvir

  ritonavir will increase the level or effect of glecaprevir/pibrentasvir by decreasing metabolism. Avoid or Use Alternate Drug. Avoid coadministration of glecaprevir/pibrentasvir with ritonavir (P-gp and a strong CYP3A4 inhibitor).

• hydroxychloroquine sulfate

  hydroxychloroquine sulfate and ritonavir both increase QTc interval. Avoid or Use Alternate Drug.

• ibrutinib

  ritonavir increases levels of ibrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of ibrutinib and strong CYP3A4 inhibitors. If a strong CYP3A4 inhibitor must be used short-term (eg, anti-infectives for =7 days), interrupt ibrutinib therapy until strong CYP3A4 inhibitor is discontinued.

• idelalisib

  ritonavir will increase the level or effect of idelalisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministered with strong CYP3A inhibitors, monitor for signs of idelalisib toxicity; follow recommendations for dosage modifications if adverse reactions occur
  
  idelalisib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Idelalisib is a strong CYP3A inhibitor; avoid coadministration with sensitive CYP3A substrates

• infigratinib

  ritonavir will increase the level or effect of infigratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• irinotecan

  ritonavir will increase the level or effect of irinotecan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• irinotecan liposomal

  ritonavir will increase the level or effect of irinotecan liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• ivosidenib

  ritonavir will increase the level or effect of ivosidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of strong CYP3A4 inhibitors with ivosidenib or replace with alternate therapies. If coadministration of a strong CYP3A4 inhibitor is unavoidable, reduce ivosidenib dose to 250 mg qDay. If the strong inhibitor is discontinued, increase ivosidenib dose (after at least 5 half-lives of the strong CYP3A4 inhibitor) to the recommended dose of 500 mg qDay. Monitor for increased risk of QTc interval prolongation.
  
  ivosidenib will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP3A4 substrates with ivosidenib or replace with alternative therapies. If coadministration is unavoidable, monitor patients for loss of therapeutic effect of these drugs.

• lapatinib

  ritonavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• larotrectinib

  ritonavir will increase the level or effect of larotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of larotrectinib with strong CYP3A4 inhibitors is unavoidable, reduce larotrectinib dose by 50%. Resume prior larotrectinib dose once CYP3A4 inhibitor discontinued for 3-5 half-lives.

• lasmiditan

  lasmiditan increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• lefamulin

  ritonavir will increase the level or effect of lefamulin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lefamulin with strong CYP3A inhibitors.

• lemborexant

  ritonavir will increase the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lemborexant with moderate or strong CYP3A inhibitors.

• levonorgestrel intrauterine

  ritonavir will increase the level or effect of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• levonorgestrel oral

  ritonavir will increase the level or effect of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate

  ritonavir, levonorgestrel oral/ethinylestradiol/ferrous bisglycinate. Other (see comment). Avoid or Use Alternate Drug. Comment: Significant changes (increase or decrease) can occur in estrogen plasma levels. Efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.

• lorlatinib

  ritonavir will increase the level or effect of lorlatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministering lorlatinib with strong CYP3A inhibitors. If unavoidable, reduce lorlatinib dose by 25 mg/day. If strong CYP3A inhibitor discontinued, increase to previous lorlatinib (dose after 3 plasma half-lives of strong CYP3A inhibitor). See monograph for further details.
  
  lorlatinib will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• lurbinectedin

  ritonavir will increase the level or effect of lurbinectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• macitentan

  ritonavir will increase the level or effect of macitentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministering macitentan with strong CYP3A4 inhibitors

• medroxyprogesterone

  ritonavir will increase the level or effect of medroxyprogesterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• mefloquine

  ritonavir increases levels of mefloquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Potential for increased toxicity. Avoid coadministration during and for 15 weeks after discontinuing mefloquine. .
  
  ritonavir increases toxicity of mefloquine by QTc interval. Avoid or Use Alternate Drug.

• methylergonovine

  ritonavir increases levels of methylergonovine by decreasing metabolism. Contraindicated.

• metoclopramide intranasal

  ritonavir will increase the level or effect of metoclopramide intranasal by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of metoclopramide intranasal and strong CYP2D6 inhibitors is not recommended since the metoclopramide intranasal dose cannot be adjusted.

• midazolam

  ritonavir increases levels of midazolam by decreasing metabolism. Contraindicated.

• midazolam intranasal

  ritonavir will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of strong CYP3A4 inhibitors with midazolam intranasal causes higher midazolam systemic exposure, which may prolong sedation.

• midostaurin

  ritonavir will increase the level or effect of midostaurin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong CYP3A4 inhibitors cannot be avoided, monitor midostaurin for increased risk of adverse reactions, especially during the first week of treatment.

• mobocertinib

  ritonavir will increase the level or effect of mobocertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  mobocertinib and ritonavir both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.

• modafinil

  ritonavir will increase the level or effect of modafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• nefazodone

  ritonavir will increase the level or effect of nefazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• neratinib

  ritonavir will increase the level or effect of neratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of neratinib with strong/moderate CYP3A4 inhibitors.

• nilotinib

  ritonavir will increase the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. May require decreased nilotinib dose or adjustment of dosing interval. Both ritonavir and nilotinib are CYP3A4 inhibitor, however, ritonavir is a strong CYP3A4 inhibitor and more likely to increase nilotinib levels and increase risk for toxicity including prolonged QT interval

• norgestrel

  ritonavir will increase the level or effect of norgestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• olaparib

  ritonavir will increase the level or effect of olaparib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong CYP3A inhibitors cannot be avoided, reduce olaparib dose to 150 mg (capsule) or 100 mg (tablet) PO BID. Do not substitute tablets with capsules.

• ombitasvir/paritaprevir/ritonavir

  ritonavir will increase the level or effect of ombitasvir/paritaprevir/ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC)

  ritonavir will increase the level or effect of ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• osimertinib

  ritonavir will increase the level or effect of osimertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of osimertinib with strong CYP3A4 inhibitors. If no other alternative treatment exists, monitor patient more closely for adverse effects.

• oxycodone

  ritonavir increases levels of oxycodone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Oxycodone dose reduction may be warranted when coadministered with strong CYP3A4 inhibitors.
  
  ritonavir increases levels of oxycodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Oxycodone dose reduction may be warranted when coadministered with strong CYP3A4 inhibitors.

• pacritinib

  ritonavir will decrease the level or effect of pacritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• palbociclib

  ritonavir will increase the level or effect of palbociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of palbociclib with strong CYP3A inhibitors. If unable to avoid, reduce palbociclib dose to 75 mg/day.

• pazopanib

  ritonavir will increase the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of pazopanib with strong CYP3A4 inhibitors if possible; if must coadminister, decrease pazopanib dose to 400 mg/day

• pemigatinib

  ritonavir will increase the level or effect of pemigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors is unavoidable, reduce pemigatinib dose (refer to drug monograph dosage modifications). After discontinuing the CYP3A4 inhibitor for 3 elimination half-lives, may resume previous pemigatinib dose.

• pexidartinib

  ritonavir will increase the level or effect of pexidartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors is unavoidable, reduce pexidartinib dose (refer to drug monograph dosage modifications). After discontinuing the CYP3A4 inhibitor for 3 elimination half-lives, may resume previous pexidartinib dose.

• pimavanserin

  ritonavir will increase the level or effect of pimavanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Decrease dose to 17 mg/day if pimavanserin is coadministered with strong CYP3A4 inhibitors.

• pomalidomide

  ritonavir increases levels of pomalidomide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir increases levels of pomalidomide by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• ponatinib

  ritonavir increases levels of ponatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Decrease ponatinib starting dose to 30 mg qDay if coadministration with strong CYP3A4 inhibitors cannot be avoided.

• pralsetinib

  ritonavir will increase the level or effect of pralsetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• propafenone

  ritonavir will increase the level or effect of propafenone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of propafenone and ritonavir is contraindicated.
  
  ritonavir increases levels of propafenone by decreasing metabolism. Contraindicated.

• quazepam

  ritonavir will increase the level or effect of quazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• quinidine

  quinidine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.
  
  ritonavir increases levels of quinidine by decreasing metabolism. Contraindicated.

• quinine

  ritonavir will increase the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Prescribing information for quinine recommends avoiding combination

• ranolazine

  ritonavir will increase the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• red yeast rice

  ritonavir will increase the level or effect of red yeast rice by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. May increase creatine kinase levels and increase risk of myopathy or rhabdomyolysis; red yeast rice contains monocolin K (reportedly identical to lovastatin)

• revefenacin

  ritonavir increases levels of revefenacin by Other (see comment). Avoid or Use Alternate Drug. Comment: OATP1B1 and OATP1B3 transport inhibitors may increase systemic exposure of revefenacin's active metabolite. Coadministration not recommended.

• ribociclib

  ritonavir will increase the level or effect of ribociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If a strong CYP3A inhibitor must be coadministered with ribociclib, reduce the ribociclib starting dose to 400 mg/day.

• rifabutin

  rifabutin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of rifabutin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rifampin

  rifampin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rifapentine

  rifapentine decreases levels of ritonavir by increasing metabolism. Contraindicated.

• rimegepant

  ritonavir will increase the level or effect of rimegepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of rimegepant by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• riociguat

  ritonavir will increase the level or effect of riociguat by decreasing metabolism. Avoid or Use Alternate Drug. Coadministration of riociguat (substrate of CYP isoenzymes 1A1, 2C8, 3A, 2J2) with strong CYP inhibitors may require a decreased initial dose of 0.5 mg PO TID; monitor for signs of hypotension and reduce dose if needed
  
  ritonavir will increase the level or effect of riociguat by Other (see comment). Avoid or Use Alternate Drug. Coadministration of riociguat (an ABCG2 [BCRP] substrate) with strong ABCG2 inhibitors may require a decreased initial dose of 0.5 mg PO TID; monitor for signs of hypotension and reduce dose if needed
  
  ritonavir will increase the level or effect of riociguat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rivaroxaban

  ritonavir increases levels of rivaroxaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of rivaroxaban and combined Pgp and strong CYP3A4 inhibitors. Combination may lead to significant increases in rivaroxaban levels and increase bleeding risk.

• roflumilast

  ritonavir will increase the level or effect of roflumilast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• romidepsin

  ritonavir will increase the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong 3A4 inhibitors should be avoided if possible.

• rosuvastatin

  ritonavir increases toxicity of rosuvastatin by Other (see comment). Avoid or Use Alternate Drug. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• ruxolitinib

  ritonavir will increase the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Reduce ruxolitinib starting dose to 10 mg BID with platelet count 100 X 10^9/L or more and concurrent use of strong CYP3A4 inhibitors; avoid with platelet counts <100 X 10^9/L

• ruxolitinib topical

  ritonavir will increase the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Reduce ruxolitinib starting dose to 10 mg BID with platelet count 100 X 10^9/L or more and concurrent use of strong CYP3A4 inhibitors; avoid with platelet counts <100 X 10^9/L

• saquinavir

  saquinavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• selpercatinib

  ritonavir will increase the level or effect of selpercatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• selumetinib

  ritonavir will increase the level or effect of selumetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors cannot be avoided, reduce selumetinib dosage (refer to selumetinib monograph for further information). After discontinuation of the strong or moderate CYP3A4 inhibitor for 3 elimination half-lives, resume selumetinib dose that was taken before initiating the inhibitor.

• sildenafil

  ritonavir will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If used concomitantly, monitor for toxicities. Patients receiving indinavir with ritonavir should receive not more than 25 mg of sildenafil for treatment of erectile dysfunction in a 48-hour period, and patients receiving other protease inhibitors should use a lower initial sildenafil dose of 25 mg. Patient taking sildenafil for PAH with ritonavir is not recommended.

• silodosin

  ritonavir will increase the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• siponimod

  ritonavir will increase the level or effect of siponimod by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of siponimod with a moderate or strong CYP3A4 inhibitor PLUS a moderate or strong CYP2C9 inhibitor is not recommended.

• sirolimus

  ritonavir will increase the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• sonidegib

  ritonavir will increase the level or effect of sonidegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sonidegib with strong CYP3A4 inhibitors.

• sotorasib

  sotorasib will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If use is unavoidable, refer to the prescribing information of the P-gp substrate for dosage modifications.

• St John's Wort

  St John's Wort decreases levels of ritonavir by increasing metabolism. Contraindicated.

• stiripentol

  ritonavir will increase the level or effect of stiripentol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• suvorexant

  ritonavir increases levels of suvorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Suvorexant not recommended with use of strong CYP3A4 inhibitors.

• tadalafil

  ritonavir will increase the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Stop tadalafil >24 hours prior to protease inhibitor (PI) initiation, restart 7 days after PI initiation at 20 mg once daily, and increase to 40 mg once daily based on tolerability.

• tamoxifen

  ritonavir, tamoxifen. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. CYP3A4 inhibition decreases metabolism of tamoxifen to N-desmethyl tamoxifen (active metabolite with similar biologic activity).

• tamsulosin

  ritonavir increases levels of tamsulosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• tepotinib

  ritonavir will increase the level or effect of tepotinib by Other (see comment). Avoid or Use Alternate Drug. Interaction not studied clinically. Metabolism and data suggest drugs that are strong CYP3A4 and P-gp inhibitors may increase tepotinib (a P-gp and CYP3A4 substrate) effects and risk of toxicities.
  
  tepotinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If concomitant use unavoidable, reduce the P-gp substrate dosage if recommended in its approved product labeling.

• thioridazine

  ritonavir will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• tofacitinib

  ritonavir increases levels of tofacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Reduce tofacitinib dose to 5 mg qDay when coadministered with potent CYP3A4 inhibitors.

• tolvaptan

  ritonavir will increase the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• topotecan

  ritonavir will increase the level or effect of topotecan by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Product labeling for PO topotecan recommends avoiding concomitant use of P-gp inhibitors; the interaction with IV topotecan may be less severe but is still likely of clinical significance

• trabectedin

  ritonavir will increase the level or effect of trabectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If strong CYP3A inhibitor must be used, short-term (eg, less than 14 days), administer strong CYP3A inhibitor 1 week after trabectedin infusion, and discontinue the day prior to next trabectedin infusion

• triazolam

  ritonavir increases levels of triazolam by decreasing metabolism. Contraindicated.

• tucatinib

  ritonavir will increase the level or effect of tucatinib by Other (see comment). Avoid or Use Alternate Drug. Coadministration of tucatinib (a CYP2C8 substrate) with a strong or moderate CYP2C8 inhibitors increases tucatinib plasma concentrations and risk of toxicities.
  
  tucatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.

• vemurafenib

  vemurafenib and ritonavir both increase QTc interval. Avoid or Use Alternate Drug. Concomitant use of vemurafenib with drugs that prolong QT interval is not recommended.
  
  ritonavir increases levels of vemurafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• vilazodone

  ritonavir increases levels of vilazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inhibitors may increase vilazodone plasma levels by 50% - Reduce daily dose to 20 mg.

• vorapaxar

  ritonavir increases levels of vorapaxar by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• voriconazole

  ritonavir will increase the level or effect of voriconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• vortioxetine

  ritonavir increases levels of vortioxetine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Decrease vortioxetine dose by 50% when coadministered with strong CYP2D6 inhibitors.

• voxelotor

  voxelotor will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.

Monitor Closely (383)

• abacavir

  ritonavir and abacavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• abemaciclib

  ritonavir will increase the level or effect of abemaciclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong CYP3A4 inhibitors increase plasma levels of abemaciclib and its metabolites. Abemaciclib dose reduction required. If a strong CYP3A4 inhibitor is discontinued, increase abemaciclib to the dose prior to initiating the strong inhibitor.

• acarbose

  ritonavir decreases effects of acarbose by pharmacodynamic antagonism. Use Caution/Monitor. New onset or exacerbation of diabetes mellitus and hyperglycemia have been reported with protease inhibitors.

• albiglutide

  ritonavir decreases effects of albiglutide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• almotriptan

  ritonavir will increase the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• alprazolam

  ritonavir will increase the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• amikacin

  ritonavir will increase the level or effect of amikacin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• amitriptyline

  ritonavir will increase the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of amitriptyline by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• amlodipine

  ritonavir will increase the level or effect of amlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• amobarbital

  amobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• apalutamide

  ritonavir will increase the level or effect of apalutamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of apalutamide with strong CYP3A4 or CYP2C8 inhibitors does not require initial dosage modification; however, dose reduction may be needed based on tolerability.

• aprepitant

  aprepitant will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• aripiprazole

  ritonavir will increase the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• armodafinil

  armodafinil will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• artemether

  ritonavir, artemether. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ritonavir may increase or decrease levels of artemether.

• artemether/lumefantrine

  ritonavir, artemether/lumefantrine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ritonavir may increase or decrease levels of lumefantrine.

• artesunate

  ritonavir will decrease the level or effect of artesunate by increasing metabolism. Use Caution/Monitor. Coadministration may decrease AUC and peak plasma concentration of active artesunate metabolite (DHA). Monitor for decreased efficacy.

• atazanavir

  atazanavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  atazanavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• atogepant

  ritonavir will increase the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Recommended atogepant dosage is 10 mg PO qDay when coadministered with strong CYP3A4 inhibitors.
  
  ritonavir will increase the level or effect of atogepant by Other (see comment). Modify Therapy/Monitor Closely. Recommended dosage of atogepant (an OATP1B1 substrate) with concomitant use of OATP inhibitors is 10 mg or 30 mg qDay.

• atomoxetine

  ritonavir will increase the level or effect of atomoxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• atorvastatin

  ritonavir will increase the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  atorvastatin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• azithromycin

  azithromycin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• bazedoxifene/conjugated estrogens

  ritonavir will increase the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of bazedoxifene/conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir decreases levels of bazedoxifene/conjugated estrogens by increasing metabolism. Use Caution/Monitor. A reduction in bazedoxifene exposure may be associated with an increase risk of endometrial hyperplasia.

• benzhydrocodone/acetaminophen

  ritonavir will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone [benzhydrocodone is prodrug of hydrocodone]) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.
  
  ritonavir will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with strong CYP3A4 inhibitors may increase hydrocodone (benzhydrocodone is prodrug of hydrocodone) plasma concentrations and can result in potentially fatal respiratory depression.

• berotralstat

  ritonavir increases levels of berotralstat by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Reduced berotralstat dose to 110 mg/day when coadministered with P-gp inhibitors.
  
  berotralstat will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor or titrate P-gp substrate dose if coadministered.

• betrixaban

  ritonavir increases levels of betrixaban by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Decrease betrixaban dose to 80 mg PO once, then 40 mg PO qDay if coadministered with a P-gp inhibitor.

• bexarotene

  ritonavir will increase the level or effect of bexarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• bortezomib

  ritonavir will increase the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• bosutinib

  bosutinib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• brentuximab vedotin

  ritonavir increases levels of brentuximab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor patients for adverse reactions. .

• brexpiprazole

  ritonavir will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer half of the usual brexpiprazole dose when coadministered with strong CYP2D6 inhibitors. If also administered with a strong/moderate CYP3A4 inhibitor, administer a quarter of brexpiprazole dose. NOTE: In MDD clinical trials, brexpiprazole dosage was not adjusted for strong CYP2D6 inhibitors (eg, paroxetine, fluoxetine); thus, CYP considerations are already factored into general dosing recommendations and brexpiprazole may be administered without dosage adjustment in patients with MDD.
  
  ritonavir will increase the level or effect of brexpiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Administer half of the usual brexpiprazole dose when coadministered with strong CYP3A4 inhibitors. If also administered with a strong/moderate CYP2D6 inhibitor, administer a quarter of brexpiprazole dose.

• bromocriptine

  ritonavir increases levels of bromocriptine by decreasing metabolism. Use Caution/Monitor. Increased levels possibly due to CYP3A4 inhibition.

• budesonide

  ritonavir will increase the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  budesonide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of budesonide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• buprenorphine

  ritonavir increases levels of buprenorphine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity.

• buprenorphine buccal

  ritonavir increases levels of buprenorphine buccal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity.

• buprenorphine subdermal implant

  ritonavir will increase the level or effect of buprenorphine subdermal implant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor patients already on buprenorphine subdermal implant who require newly-initiated treatment with CYP3A4 inhibitors for signs and symptoms of overmedication. If the dose of the concomitant CYP3A4 inhibitor cannot be reduced or discontinued, implant removal may be necessary and the patient should then be treated with a buprenorphine dosage form that permits dose adjustments. If a CYP3A4 inhibitor is discontinued in a patient who has been stabilized on buprenorphine, monitor the patient for withdrawal.

• buprenorphine transdermal

  ritonavir will increase the level or effect of buprenorphine transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• buprenorphine, long-acting injection

  ritonavir will increase the level or effect of buprenorphine, long-acting injection by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Patients who transfer to buprenorphine long-acting injection from transmucosal buprenorphine coadministered with CYP3A4 inhibitors should be monitored to ensure buprenorphine plasma levels are adequate. Within 2 weeks, if signs and symptoms of buprenorphine toxicity or overdose occur and the concomitant CYP3A4 inhibitor cannot be reduced or discontinued, transition the patient back to a buprenorphine formulation that permits dose adjustments.

• bupropion

  ritonavir decreases levels of bupropion by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Ritonavir decreases levels of bupropion by inducing CYP2B6. Bupropion levels decreased by 20-80%, increased doses of bupropion may be required .

• buspirone

  ritonavir will increase the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• butabarbital

  butabarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• butalbital

  butalbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cabazitaxel

  ritonavir increases levels of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Avoid coadministration.

• cabozantinib

  ritonavir will increase the level or effect of cabozantinib by Other (see comment). Use Caution/Monitor. MRP2 inhibitors increase cabozantinib toxicity

• calcifediol

  ritonavir, calcifediol. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. CYP450 inhibitors may inhibit enzymes involved in vitamin D metabolism (CYP24A1 and CYP27B1). This may alter serum levels of calcifediol and decrease the conversion of calcifediol to calcitriol. Dose adjustment of calcifediol may be required, and serum 25­hydroxyvitamin D, intact PTH, and serum calcium concentrations should be closely monitored when initiating or discontinuing a strong CYP3A4 inhibitor.

• canagliflozin

  ritonavir decreases levels of canagliflozin by increasing metabolism. Use Caution/Monitor. Coadministration with potent UGT enzyme inducers: Consider increasing dose to 300 mg qDay if 100 mg/day tolerate and additional glycemic control required (eGFR must be >60 mL/min/1.73 m2 to increase dose); if eGFR <60 mL/min/1.73 m2, consider using a different antihyperglycemic agent.

• cannabidiol

  ritonavir will increase the level or effect of cannabidiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider reducing the cannabidiol dose when coadministered with a strong CYP3A4 inhibitor.

• carbamazepine

  ritonavir will increase the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor plasma levels when used concomitantly

• cariprazine

  ritonavir will increase the level or effect of cariprazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with strong CYP3A4 inhibitors requires cariprazine dose reduction. See Dosage Modification section in drug monograph.

• carvedilol

  ritonavir will increase the level or effect of carvedilol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• cenobamate

  cenobamate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase dose of CYP3A4 substrate, as needed, when coadministered with cenobamate.

• ceritinib

  ritonavir increases levels of ceritinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• cetirizine

  ritonavir increases levels of cetirizine by decreasing metabolism. Use Caution/Monitor.

• chlordiazepoxide

  ritonavir increases levels of chlordiazepoxide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Use alternatives if available. Potential for increased toxicity. Consider lowering benzodiazepine dose.

• chlorpropamide

  ritonavir, chlorpropamide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of chlorpropamide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• cholic acid

  ritonavir increases toxicity of cholic acid by decreasing elimination. Modify Therapy/Monitor Closely. Avoid concomitant use of inhibitors of the bile salt efflux pump (BSEP). May exacerbate accumulation of conjugated bile salts in the liver and result in clinical symptoms. If concomitant use is necessary, monitor serum transaminases and bilirubin.

• ciclesonide inhaled

  ritonavir increases levels of ciclesonide inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of Cushing's syndrome or adrenal suppression.

• cilostazol

  ritonavir will increase the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cinacalcet

  ritonavir will increase the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• citalopram

  ritonavir increases levels of citalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased risk of serotonin syndrome. ECG monitoring is recommended, along with drugs that may prolong the QT interval.

• clarithromycin

  clarithromycin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• clomipramine

  ritonavir will increase the level or effect of clomipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• clonazepam

  ritonavir increases levels of clonazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Use alternatives if available. Consider lowering benzodiazepine dose.

• clopidogrel

  ritonavir will decrease the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Inhibition of CYP3A4 will reduce clopidogrel bioactivation

• clotrimazole

  clotrimazole will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• clozapine

  ritonavir will increase the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cocaine

  ritonavir will increase the level or effect of cocaine by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor.

• codeine

  ritonavir will decrease the level or effect of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.

• conivaptan

  conivaptan will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conjugated estrogens

  ritonavir will increase the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• conjugated estrogens, vaginal

  ritonavir will increase the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of conjugated estrogens, vaginal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• cortisone

  ritonavir will increase the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  cortisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of cortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• crizotinib

  ritonavir increases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use of strong CYP3A inhibitors should be avoided. ECG monitoring is recommended, along with drugs that may prolong the QT interval.
  
  crizotinib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• crofelemer

  crofelemer increases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Crofelemer has the potential to inhibit CYP3A4 at concentrations expected in the gut; unlikely to inhibit systemically because minimally absorbed.

• cyclophosphamide

  ritonavir will increase the level or effect of cyclophosphamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of cyclophosphamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cyclosporine

  ritonavir will increase the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of cyclosporine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dabigatran

  ritonavir will increase the level or effect of dabigatran by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Atrial fibrillation: Avoid coadministering dabigatran with P-gp inhibitors if CrCl <30 mL/min. DVT/PE treatment: Avoid coadministering dabigatran with P-gp inhibitors if CrCl <50 mL/min

• darifenacin

  darifenacin will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• darolutamide

  ritonavir will increase the level or effect of darolutamide by Other (see comment). Modify Therapy/Monitor Closely. Darolutamide is a P-gp and CYP3A4 substrate. Closely monitor for increased adverse reactions and modify dose of darolutamide as needed when coadministered with drugs that are both P-gp and strong or moderate CYP3A4 inhibitors.

• darunavir

  darunavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  darunavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• dasatinib

  dasatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• daunorubicin

  ritonavir will increase the level or effect of daunorubicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• deferasirox

  ritonavir decreases levels of deferasirox by Other (see comment). Use Caution/Monitor. Comment: Avoid concomitant use of potent UGT inducers with deferasirox. If co-administration is required then consider increasing initial dose of deferasirox to 30 mg/kg and monitor ferritin levels and clinical response.

• deflazacort

  ritonavir will increase the level or effect of deflazacort by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Decrease deflazacort dose to one-third of the recommended dose if coadministered with moderate or strong CYP3A4 inhibitors.
  
  ritonavir will increase the level or effect of deflazacort by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• desipramine

  ritonavir will increase the level or effect of desipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of desipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• desvenlafaxine

  ritonavir increases levels of desvenlafaxine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .

• deutetrabenazine

  ritonavir will increase the level or effect of deutetrabenazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Strong CYP2D6 inhibitors increase the systemic exposure to the active dihydro-metabolites of deutetrabenazine by approximately 3-fold. Do not exceed 18 mg/dose and 36 mg/day of deutetrabenazine if coadministered with strong CYP2D6 inhibitors.

• dexamethasone

  ritonavir will increase the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  dexamethasone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of dexamethasone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dexlansoprazole

  ritonavir will increase the level or effect of dexlansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• DHEA, herbal

  DHEA, herbal will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• diazepam

  ritonavir increases levels of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Use alternatives if available.

• diazepam intranasal

  ritonavir will increase the level or effect of diazepam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inhibitors may decrease rate of diazepam elimination, thereby increasing adverse reactions to diazepam.

• diazoxide

  ritonavir increases effects of diazoxide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• didanosine

  ritonavir and didanosine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.
  
  ritonavir will decrease the level or effect of didanosine by increasing gastric pH. Applies only to oral form of both agents. Use Caution/Monitor. Didanosine should be taken 1 hour prior or 2 hours after administration of lopinavir/ritonavir oral solution.

• dienogest/estradiol valerate

  ritonavir will increase the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Significant changes (increase or decrease) in plasma levels of estrogen and progestin have been seen when HIV protease inhibitors are administered. Monitor for potential adverse effects such as nausea, irregular uterine bleeding, breast tenderness and headache.

• digoxin

  ritonavir will increase the level or effect of digoxin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Plasma concentrations and pharmacologic effects of digoxin may be increased by ritonavir. Monitor for increased effects of digoxin.
  
  ritonavir increases levels of digoxin by decreasing renal clearance. Use Caution/Monitor.
  
  ritonavir increases levels of digoxin by decreasing hepatic clearance. Use Caution/Monitor.

• diltiazem

  diltiazem will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• docetaxel

  ritonavir will increase the level or effect of docetaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dofetilide

  ritonavir increases levels of dofetilide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Use alternatives if available. Increased risk of QT prolongation and cardiac arrhythmias.

• doravirine

  ritonavir will increase the level or effect of doravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of doravirine and CYP3A4 inhibitors may increase plasma concentrations and toxicities of doravirine.

• doxepin

  ritonavir will increase the level or effect of doxepin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• doxepin cream

  ritonavir will increase the level or effect of doxepin cream by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• doxorubicin

  ritonavir will increase the level or effect of doxorubicin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of doxorubicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• doxorubicin liposomal

  ritonavir will increase the level or effect of doxorubicin liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of doxorubicin liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dronabinol

  ritonavir will increase the level or effect of dronabinol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dronabinol is a CYP3A4 substrate.

• dronedarone

  dronedarone will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• duloxetine

  ritonavir will increase the level or effect of duloxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• duvelisib

  ritonavir will increase the level or effect of duvelisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with a strong CYP3A4 inhibitor increases duvelisib AUC, which may increase the risk of duvelisib toxicities. Reduce duvelisib dose to 15 mg BID when coadministered with a strong CYP3A4 inhibitor.
  
  ritonavir will increase the level or effect of duvelisib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• efavirenz

  efavirenz will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir and efavirenz both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• elagolix

  elagolix will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  elagolix decreases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak-to-moderate CYP3A4 inducer. Monitor CYP3A substrates if coadministered. Consider increasing CYP3A substrate dose if needed.

• eletriptan

  ritonavir will increase the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• eliglustat

  eliglustat increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the P-gp substrate and titrate to clinical effect.
  
  eliglustat increases levels of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the concomitant drug and titrate to clinical effect.

• eluxadoline

  ritonavir increases levels of eluxadoline by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. As a precautionary measure due to incomplete information on the metabolism of eluxadoline, use caution when coadministered with strong CYP2D6 inhibitors.

• elvitegravir

  ritonavir will increase the level or effect of elvitegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• emtricitabine

  ritonavir and emtricitabine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• encorafenib

  encorafenib, ritonavir. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Encorafenib both inhibits and induces CYP3A4 at clinically relevant plasma concentrations. Coadministration of encorafenib with sensitive CYP3A4 substrates may result in increased toxicity or decreased efficacy of these agents.

• enfortumab vedotin

  ritonavir increases toxicity of enfortumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Enfortumab vedotin is an antibody-drug conjugate that releases monomethylauristatin E (MMAE) via proteolytic cleavage. MMAE is primarily metabolized by CYP3A4 in vitro. Coadministration with strong CYP3A4 inhibitors may increase free MMAE exposure, which may increase the incidence or severity of toxicities.

• enfuvirtide

  ritonavir and enfuvirtide both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• erlotinib

  ritonavir will increase the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• erythromycin base

  erythromycin base will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• erythromycin ethylsuccinate

  erythromycin ethylsuccinate will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• erythromycin lactobionate

  erythromycin lactobionate will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• erythromycin stearate

  erythromycin stearate will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• escitalopram

  ritonavir increases levels of escitalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of serotonin syndrome.

• eslicarbazepine acetate

  eslicarbazepine acetate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• esomeprazole

  ritonavir will increase the level or effect of esomeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estradiol

  ritonavir will increase the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of estradiol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• estradiol vaginal

  ritonavir will increase the level or effect of estradiol vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with CYP3A4 inhibitors may increase plasma concentrations of estrogens and toxicities.

• estrogens conjugated synthetic

  ritonavir will increase the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of estrogens conjugated synthetic by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• estrogens esterified

  ritonavir will increase the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estropipate

  ritonavir will increase the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of estropipate by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• eszopiclone

  ritonavir increases levels of eszopiclone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce eszopiclone starting dose to 1 mg/day.

• ethosuximide

  ritonavir increases levels of ethosuximide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• etonogestrel

  ritonavir will increase the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• etoposide

  ritonavir will increase the level or effect of etoposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of etoposide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• etravirine

  ritonavir will increase the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• exenatide injectable solution

  ritonavir decreases effects of exenatide injectable solution by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• exenatide injectable suspension

  ritonavir decreases effects of exenatide injectable suspension by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors.

• ezogabine

  ezogabine, ritonavir. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Slight and transient QT-prolongation observed with ezogabine, particularly when dose titrated to 1200 mg/day. QT interval should be monitored when ezogabine is prescribed with agents known to increase QT interval.

• fedratinib

  fedratinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP3A4 substrates as necessary.
  
  fedratinib will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP2D6 substrates as necessary.

• felodipine

  ritonavir will increase the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  felodipine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• fesoterodine

  ritonavir will increase the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fluconazole

  fluconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fludrocortisone

  ritonavir will increase the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  fludrocortisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of fludrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• flunisolide inhaled

  ritonavir will increase the level or effect of flunisolide inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• flurazepam

  ritonavir increases levels of flurazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Use alternatives if available. Consider lowering benzodiazepine dose.

• fluticasone furoate

  ritonavir will increase the level or effect of fluticasone furoate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inhibitors may increase fluticasone systemic exposure

• fluticasone inhaled

  ritonavir will increase the level or effect of fluticasone inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inhibitors may increase fluticasone systemic exposure

• fluvastatin

  ritonavir increases toxicity of fluvastatin by Other (see comment). Use Caution/Monitor. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• fluvoxamine

  fluvoxamine will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fosamprenavir

  fosamprenavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  fosamprenavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• fosphenytoin

  fosphenytoin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  fosphenytoin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• fostamatinib

  ritonavir will increase the level or effect of fostamatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong CYP3A4 inhibitors may increase exposure to R406 (fostamatinib major active metabolite). Monitor for toxicities that may require fostamatinib dose reduction.
  
  fostamatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Concomitant use of fostamatinib may increase concentrations of P-gp substrates. Monitor for toxicities of the P-gp substrate drug that may require dosage reduction when given concurrently with fostamatinib.

• garlic

  garlic decreases levels of ritonavir by unknown mechanism. Use Caution/Monitor.

• gefitinib

  ritonavir increases levels of gefitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of strong CYP3A4 inhibitors may increase risk for gefitinib adverse effects.

• gentamicin

  ritonavir will increase the level or effect of gentamicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• glecaprevir/pibrentasvir

  glecaprevir/pibrentasvir will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• glimepiride

  ritonavir, glimepiride. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of glimepiride. Use alternatives if available. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• glipizide

  ritonavir, glipizide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of glipizide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• glyburide

  ritonavir, glyburide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of glyburide. Use alternatives if available. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• grapefruit

  grapefruit will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• griseofulvin

  griseofulvin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• guanfacine

  ritonavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

• haloperidol

  ritonavir will increase the level or effect of haloperidol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  haloperidol and ritonavir both increase QTc interval. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of haloperidol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• hydrocodone

  ritonavir will increase the level or effect of hydrocodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.
  
  ritonavir will increase the level or effect of hydrocodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with CYP3A4 inhibitors may increase hydrocodone plasma concentrations and can result in potentially fatal respiratory depression

• hydrocortisone

  ritonavir will increase the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  hydrocortisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of hydrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• hydromorphone

  ritonavir will increase the level or effect of hydromorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• hydroxyprogesterone caproate

  ritonavir will increase the level or effect of hydroxyprogesterone caproate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ifosfamide

  ritonavir will decrease the level or effect of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of CYP3A4 inhibitors may decrease the metabolism of ifosfamide to its active alkylating metabolites and decrease the efficacy of ifosfamide.
  
  ritonavir increases effects of ifosfamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Coadministration of ifosfamide with CYP2B6 inducers may increase metabolism of ifosfamide to its metabolite. Monitor for increased effects/toxicities if combined with CYP2B6 inducers.

• iloperidone

  ritonavir will increase the level or effect of iloperidone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  iloperidone increases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Iloperidone is a time-dependent CYP3A inhibitor and may lead to increased plasma levels of drugs predominantly eliminated by CYP3A4.

• imatinib

  ritonavir will increase the level or effect of imatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• imipramine

  ritonavir will increase the level or effect of imipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• indacaterol, inhaled

  ritonavir increases levels of indacaterol, inhaled by Other (see comment). Use Caution/Monitor. Comment: Data suggests that systemic clearance is influenced by modulation of both P-gp and CYP3A4 activities. No dose adjustment is warranted at the 75 mcg dose.
  
  indacaterol, inhaled, ritonavir. QTc interval. Use Caution/Monitor. Drugs that are known to prolong the QTc interval may have an increased the risk of ventricular arrhythmias.

• indinavir

  indinavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  indinavir will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  indinavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• insulin aspart

  ritonavir decreases effects of insulin aspart by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin degludec

  ritonavir decreases effects of insulin degludec by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. HIV protease inhibitors may cause new onset diabetes mellitus (DM), exacerbate existing DM, and cause hyperglycemia due to insulin resistance.

• insulin degludec/insulin aspart

  ritonavir decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. HIV protease inhibitors may cause new onset diabetes mellitus (DM), exacerbate existing DM, and cause hyperglycemia due to insulin resistance.

• insulin detemir

  ritonavir decreases effects of insulin detemir by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin glargine

  ritonavir decreases effects of insulin glargine by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin glulisine

  ritonavir decreases effects of insulin glulisine by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin inhaled

  ritonavir decreases effects of insulin inhaled by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. HIV protease inhibitors may cause new onset diabetes mellitus (DM), exacerbate existing DM, and cause hyperglycemia due to insulin resistance.

• insulin lispro

  ritonavir decreases effects of insulin lispro by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin NPH

  ritonavir decreases effects of insulin NPH by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin regular human

  ritonavir decreases effects of insulin regular human by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• isavuconazonium sulfate

  ritonavir will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• isoniazid

  isoniazid will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• istradefylline

  ritonavir will increase the level or effect of istradefylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Do not exceed istradefylline 20 mg/day if coadministered with strong CYP3A4 inhibitors.
  
  istradefylline will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of CYP3A4 substrates in clinical trials. This effect was not observed with istradefylline 20 mg/day. Consider dose reduction of sensitive CYP3A4 substrates.
  
  istradefylline will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of P-gp substrates in clinical trials. Consider dose reduction of sensitive P-gp substrates.

• itraconazole

  ritonavir will increase the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Limit itraconazole dose to 200 mg/day in patients receiving ritonavir.

• ivacaftor

  ritonavir will increase the level or effect of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce ivacaftor dose if coadministered with strong CYP3A4 inhibitors. See specific ivacaftor-containing product for precise dosage modification.
  
  ivacaftor increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Ivacaftor and its M1 metabolite has the potential to inhibit P-gp; may significantly increase systemic exposure to sensitive P-gp substrates with a narrow therapeutic index.

• ivermectin

  ritonavir will increase the level or effect of ivermectin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• ixabepilone

  ritonavir will increase the level or effect of ixabepilone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ketamine

  ritonavir will decrease the level or effect of ketamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ketoconazole

  ketoconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ketoconazole dose is not to exceed 200 mg/day when concurrently used with ritonavir.
  
  ketoconazole will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• lacosamide

  ritonavir increases levels of lacosamide by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Use alternatives if available. Increased risk of PR prolongation and cardiac arrhythmias.
  
  ritonavir, lacosamide. Either increases levels of the other by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider decreasing lacosamide dose when coadministered with strong CYP3A4 inhibitors.

• lamivudine

  ritonavir and lamivudine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• lamotrigine

  ritonavir will decrease the level or effect of lamotrigine by increasing metabolism. Use Caution/Monitor. Combination may decrease lamotrigine levels by 50%. Adjust lamotrigine dose as needed when starting, stopping, or changing ritonavir dose. Similar interactions are possible with other RTV-boosted PIs.

• lapatinib

  lapatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  lapatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• letermovir

  ritonavir increases levels of letermovir by decreasing metabolism. Use Caution/Monitor. Coadminstration of letermovir, an OATP1B1/3 substrate, with OATP1B1/3 inhibitors may increase letermovir plasma concentrations.
  
  letermovir increases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levamlodipine

  ritonavir will increase the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levocetirizine

  ritonavir increases levels of levocetirizine by decreasing metabolism. Use Caution/Monitor.

• levoketoconazole

  levoketoconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ketoconazole dose is not to exceed 200 mg/day when concurrently used with ritonavir.
  
  levoketoconazole will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• levomilnacipran

  ritonavir will increase the level or effect of levomilnacipran by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Do not exceed 80 mg/day of levomilnacipran when coadministered with strong CYP3A4 inhibitors

• linagliptin

  ritonavir increases levels of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .
  
  ritonavir decreases effects of linagliptin by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• liraglutide

  ritonavir decreases effects of liraglutide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• lofepramine

  ritonavir will increase the level or effect of lofepramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• lofexidine

  ritonavir will increase the level or effect of lofexidine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Concomitant use of lofexidine with strong CYP2D6 inhibitors may increase lofexidine plasma levels. Monitor for symptoms of orthostasis and bradycardia if coadministered with a CYP2D6 inhibitor. Consider lofexidine dose reduction.

• lomitapide

  lomitapide increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Consider reducing dose when used concomitantly with lomitapide.

• loperamide

  ritonavir will increase the level or effect of loperamide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• lopinavir

  ritonavir will increase the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• loratadine

  ritonavir will increase the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  loratadine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• lorcaserin

  lorcaserin will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• losartan

  ritonavir will increase the level or effect of losartan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lumacaftor/ivacaftor

  ritonavir increases levels of lumacaftor/ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong CYP3A inhibitors do not impact lumacaftor exposure, but increased ivacaftor exposure by 4.3-fold. Due to the induction effect of lumacaftor on CYP3A, at steady-state the net exposure of ivacaftor is not expected to exceed that when given in the absence of lumacaftor at a dose of 150 mg q12hr (the approved dose of ivacaftor monotherapy). Therefore, no dose adjustment is necessary when CYP3A inhibitors are initiated in patients currently taking lumacaftor/ivacaftor. However, when initiating lumacaftor/ivacaftor in patients taking strong CYP3A inhibitors, reduce the dose to 1 tablet daily (lumacaftor 200 mg/ivacaftor 125 mg total daily dose) for the first week of treatment to allow for the steady-state induction effect of lumacaftor. Following this period, continue with the recommended daily dose. No dose adjustment is required for moderate or weak CYP3A4 inhibitors.

• lumateperone

  ritonavir will increase the level or effect of lumateperone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce lumateperone dose to 10.5 mg/day if coadministered with strong CYP3A4 inhibitors.

• lumefantrine

  ritonavir, lumefantrine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ritonavir may increase or decrease levels of lumefantrine.

• maraviroc

  ritonavir will increase the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Decrease maraviroc dose to 150 mg BID when coadministered with strong CYP3A4 inhibitors
  
  ritonavir will increase the level or effect of maraviroc by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• marijuana

  marijuana will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of marijuana by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• meperidine

  ritonavir increases levels of meperidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• mestranol

  ritonavir will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir decreases levels of mestranol by increasing metabolism. Use Caution/Monitor. May result in contraceptive failure; use additional or alternative method.

• metformin

  ritonavir decreases effects of metformin by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• methadone

  ritonavir will increase the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir decreases effects of methadone by Other (see comment). Use Caution/Monitor. Comment: Ritonavir may induce the metabolism of methadone and/or induce the p glycoprotein pathway that pumps drugs out of the CNS.

• methamphetamine

  ritonavir will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• methylprednisolone

  ritonavir will increase the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  methylprednisolone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of methylprednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• metoprolol

  ritonavir will increase the level or effect of metoprolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• metronidazole

  metronidazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• mexiletine

  ritonavir will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Monitor patients for signs and symptoms of mexiletine toxicity (nausea, dizziness, cardiac arrhythmias). Therapeutic concentration monitoring is recommended for mexiletine, if available. Reduce doses of mexiletine as required.

• miconazole vaginal

  miconazole vaginal will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• midazolam

  ritonavir will increase the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• mifepristone

  ritonavir will increase the level or effect of mifepristone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Do not exceed mifepristone 300 mg/day for Cushing syndrome when coadministered with strong CYP3A4 inhibitors
  
  mifepristone, ritonavir. QTc interval. Modify Therapy/Monitor Closely. Use alternatives if available.
  
  mifepristone will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• miglitol

  ritonavir decreases effects of miglitol by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• mipomersen

  mipomersen, ritonavir. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Both drugs have potential to increase hepatic enzymes; monitor LFTs.

• mirabegron

  mirabegron will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• mirtazapine

  ritonavir increases levels of mirtazapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• mitotane

  mitotane decreases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Mitotane is a strong inducer of cytochrome P-4503A4; monitor when coadministered with CYP3A4 substrates for possible dosage adjustments.

• mometasone inhaled

  ritonavir increases levels of mometasone inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of Cushing's syndrome or adrenal suppression.

• mometasone, intranasal

  ritonavir will increase the level or effect of mometasone, intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• morphine

  ritonavir will increase the level or effect of morphine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• nafcillin

  nafcillin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• naldemedine

  ritonavir increases levels of naldemedine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor naldemedine for potential adverse effects if coadministered with strong or moderate CYP3A4 inhibitors.
  
  ritonavir increases levels of naldemedine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor naldemedine for potential adverse effects if coadministered with P-gp inhibitors.

• nateglinide

  ritonavir decreases effects of nateglinide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• nebivolol

  ritonavir will increase the level or effect of nebivolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• nefazodone

  nefazodone will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nefazodone will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• nelfinavir

  nelfinavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of nelfinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  nelfinavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• neomycin PO

  ritonavir will increase the level or effect of neomycin PO by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• netupitant/palonosetron

  ritonavir will increase the level or effect of netupitant/palonosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Netupitant is mainly metabolized by CYP3A4; no dosage adjustment is required

• nevirapine

  nevirapine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir and nevirapine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of nevirapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nicardipine

  ritonavir will increase the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nicardipine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• nifedipine

  nifedipine will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nifedipine will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• nilotinib

  nilotinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nilotinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• nintedanib

  ritonavir increases levels of nintedanib by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. If nintedanib adverse effects occur, management may require interruption, dose reduction, or discontinuation of therapy .

• nisoldipine

  ritonavir will increase the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• norethindrone

  ritonavir will increase the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nortriptyline

  ritonavir will increase the level or effect of nortriptyline by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• olanzapine

  ritonavir decreases levels of olanzapine by increasing metabolism. Use Caution/Monitor.

• oliceridine

  ritonavir will increase the level or effect of oliceridine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.
  
  ritonavir will increase the level or effect of oliceridine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.

• olodaterol inhaled

  ritonavir and olodaterol inhaled both increase QTc interval. Use Caution/Monitor. Drugs that prolong the QTc interval and may potentiate the effects of beta2 agonists on the cardiovascular system; increased risk of ventricular arrhythmias

• omeprazole

  ritonavir will increase the level or effect of omeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ondansetron

  ritonavir and ondansetron both increase QTc interval. Use Caution/Monitor. Avoid with congenital long QT syndrome; ECG monitoring recommended with concomitant medications that prolong QT interval, electrolyte abnormalities, CHF, or bradyarrhythmias. May increase ondansetron levels.
  
  ritonavir will increase the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• orlistat

  orlistat will decrease the level or effect of ritonavir by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Loss of virological control reported in HIV-infected patients taking orlistat concomitantly. Exact mechanism is unclear, but may include a drug-drug interaction that inhibits systemic absorption of the antiretroviral drug. Monitor HIV RNA levels frequently and if increased HIV viral load confirmed, discontinue orlistat.

• osilodrostat

  ritonavir will increase the level or effect of osilodrostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce dose of osilodrostat, a CYP3A4 substrate, by half when coadministered with a strong CYP3A4 inhibitor.

• ospemifene

  ritonavir increases levels of ospemifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• oxcarbazepine

  oxcarbazepine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• oxymorphone

  ritonavir will increase the level or effect of oxymorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• ozanimod

  ritonavir will increase the level or effect of ozanimod by Other (see comment). Modify Therapy/Monitor Closely. Coadministration of ozanimod (a CYP2C8 substrate) with strong CYP2C8 inhibitors increases the exposure of the active metabolites (CC112273 and CC1084037) of ozanimod, which may increase the risk of ozanimod adverse reactions. Therefore, coadministration of ozanimod with strong CYP2C8 inhibitors is not recommended.
  
  ozanimod and ritonavir both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties.

• paclitaxel

  ritonavir will increase the level or effect of paclitaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of paclitaxel by Other (see comment). Modify Therapy/Monitor Closely. Paclitaxel levels/toxicity may increase when coadministered with CYP2C8 inhibitors

• paclitaxel protein bound

  ritonavir will increase the level or effect of paclitaxel protein bound by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of paclitaxel protein bound by Other (see comment). Modify Therapy/Monitor Closely. Paclitaxel levels/toxicity may increase when coadministered with CYP2C8 inhibitors

• paliperidone

  ritonavir will increase the level or effect of paliperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• panobinostat

  ritonavir increases levels of panobinostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce panobinostat starting dose to 10 mg if coadministered with strong CYP3A4 inhibitors.

• paricalcitol

  ritonavir increases levels of paricalcitol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• paromomycin

  ritonavir will increase the level or effect of paromomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• paroxetine

  ritonavir will increase the level or effect of paroxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• peginterferon alfa 2b

  peginterferon alfa 2b, ritonavir. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate. The concomitant use of interferons and anti-retroviral protease inhibitors should be done with caution as both can cause hepatic damage. .

• pentobarbital

  pentobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• perampanel

  ritonavir will increase the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• phenobarbital

  phenobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  phenobarbital will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• phenytoin

  phenytoin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  phenytoin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• pitavastatin

  ritonavir increases toxicity of pitavastatin by Other (see comment). Use Caution/Monitor. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• pitolisant

  ritonavir will increase the level or effect of pitolisant by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If coadministered with strong CYP2D6 inhibitors, initiate pitolisant at 8.9 mg/day and increase after 7 days to maximum of 17.8 mg/day. For patients currently taking pitolisant, reduce pitolisant dose by half upon initiating strong CYP2D6 inhibitors.

• polatuzumab vedotin

  ritonavir will increase the level or effect of polatuzumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Polatuzumab undergoes catabolism to small peptides, amino acids, monomethyl auristatin E (MMAE), and unconjugated MMAE-related catabolites. MMAE is a CYP3A4 substrate. Coadministration of polatuzumab vedotin with a strong CYP3A4 inhibitor may increase unconjugated MMAE AUC, which may increase polatuzumab vedotin toxicities.

• ponatinib

  ponatinib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• posaconazole

  posaconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of posaconazole by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• pramlintide

  ritonavir decreases effects of pramlintide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• pravastatin

  ritonavir increases toxicity of pravastatin by Other (see comment). Use Caution/Monitor. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• praziquantel

  ritonavir will increase the level or effect of praziquantel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• prednisolone

  ritonavir will increase the level or effect of prednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of prednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• prednisone

  ritonavir will increase the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  prednisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of prednisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• primidone

  primidone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• progesterone intravaginal gel

  ritonavir will increase the level or effect of progesterone intravaginal gel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• progesterone micronized

  ritonavir will increase the level or effect of progesterone micronized by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• progesterone, natural

  ritonavir will increase the level or effect of progesterone, natural by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• propranolol

  ritonavir will increase the level or effect of propranolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• quercetin

  quercetin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• quetiapine

  ritonavir will increase the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  quetiapine, ritonavir. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Avoid use with drugs that prolong QT and in patients with risk factors for prolonged QT interval. Postmarketing cases show QT prolongation with overdose in patients with concomitant illness or with drugs known to cause electrolyte imbalance or prolong QT.

• quinidine

  ritonavir will increase the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• quinupristin/dalfopristin

  quinupristin/dalfopristin will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ranolazine

  ranolazine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• repaglinide

  ritonavir will increase the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ribociclib

  ribociclib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• rifabutin

  ritonavir increases levels of rifabutin by decreasing metabolism. Use Caution/Monitor.

• rifampin

  rifampin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• rifapentine

  rifapentine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• rifaximin

  ritonavir increases levels of rifaximin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• rilpivirine

  ritonavir increases levels of rilpivirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No dose adjustment is required during concurrent use.
  
  rilpivirine increases toxicity of ritonavir by QTc interval. Use Caution/Monitor. Rilpivirine should be used with caution when co-administered with a drug with a known risk of Torsade de Pointes.

• ripretinib

  ritonavir will increase the level or effect of ripretinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with a strong CYP3A inhibitor will increase systemic exposure to ripretinib and its active metabolite (DP-5439), which may increase risk of adverse reactions.

• risperidone

  ritonavir will increase the level or effect of risperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• roflumilast

  ritonavir will decrease the level or effect of roflumilast by affecting hepatic enzyme CYP1A2 metabolism. Modify Therapy/Monitor Closely. Concomitant therapy may reduce therapeutic effectiveness.

• rolapitant

  rolapitant will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Rolapitant may increase plasma concentrations of CYP2D6 substrates for at least 28 days following rolapitant administration.

• romidepsin

  ritonavir will increase the level or effect of romidepsin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• rosiglitazone

  ritonavir decreases effects of rosiglitazone by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• rosuvastatin

  ritonavir will increase the level or effect of rosuvastatin by decreasing metabolism. Use Caution/Monitor.

• rucaparib

  rucaparib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP3A4 substrates, if clinically indicated.

• rufinamide

  rufinamide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sacubitril/valsartan

  ritonavir will increase the level or effect of sacubitril/valsartan by Other (see comment). Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic uptake transporter OATP1B1; coadministration with OATP1B1 inhibitors may increase valsartan systemic exposure
  
  ritonavir will increase the level or effect of sacubitril/valsartan by Mechanism: decreasing hepatic clearance. Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic efflux transporter MRP2; coadministration of inhibitors of the efflux transporter may increase the systemic exposure to valsartan

• saquinavir

  ritonavir will increase the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Saquinavir is intended to be administered with ritonavir (boosted therapy). The combination has shown to cause dose-dependent QT and PR interval prolongation. Caution in treatment naïve patients. Reduce starting dose and perform an on-treatment ECG after approximately 10 days.
  
  ritonavir will increase the level or effect of saquinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir and saquinavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• sarecycline

  sarecycline will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor for toxicities of P-gp substrates that may require dosage reduction when coadministered with P-gp inhibitors.

• saxagliptin

  ritonavir will increase the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Limit saxagliptin dose to 2.5 mg/day when coadministered with strong CYP3A4 inhibitors

• secobarbital

  secobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sertraline

  ritonavir increases levels of sertraline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased risk of serotonin syndrome.

• silodosin

  ritonavir will increase the level or effect of silodosin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• sirolimus

  ritonavir will increase the level or effect of sirolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• sitagliptin

  ritonavir decreases effects of sitagliptin by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• solifenacin

  ritonavir will increase the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sorafenib

  ritonavir will increase the level or effect of sorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• St John's Wort

  St John's Wort will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• stavudine

  ritonavir and stavudine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• stiripentol

  stiripentol, ritonavir. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.
  
  stiripentol will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Consider reducing the dose of P-glycoprotein (P-gp) substrates, if adverse reactions are experienced when administered concomitantly with stiripentol.

• streptomycin

  ritonavir will increase the level or effect of streptomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• sufentanil SL

  ritonavir will increase the level or effect of sufentanil SL by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of sufentanil SL with any CYP3A4 inhibitor may increase sufentanil plasma concentration, and, thereby increase or prolonged adverse effects, including potentially fatal respiratory depression.

• sunitinib

  ritonavir will increase the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tacrolimus

  ritonavir will increase the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of tacrolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• tacrolimus ointment

  ritonavir will increase the level or effect of tacrolimus ointment by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• talazoparib

  ritonavir will increase the level or effect of talazoparib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Talazoparib is a P-glycoprotein (P-gp) substrate; coadministration with P-gp inhibitors may increase talazoparib systemic exposure.

• tamoxifen

  ritonavir, tamoxifen. affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. CYP2D6 inhibition decreases metabolism of tamoxifen to hydroxytamoxifen, and N-desmethyl tamoxifen to endoxifen (active metabolites with 100-fold greater affinity for estrogen receptor); decreased endoxifen levels may result in poor clinical outcome.

• tamsulosin

  ritonavir increases levels of tamsulosin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• tasimelteon

  ritonavir will increase the level or effect of tasimelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tazemetostat

  ritonavir will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  tazemetostat will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tecovirimat

  tecovirimat will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.

• temsirolimus

  ritonavir will increase the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• teniposide

  ritonavir will increase the level or effect of teniposide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of teniposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tenofovir DF

  ritonavir and tenofovir DF both increase risk of immune reconstitution syndrome. Use Caution/Monitor.
  
  ritonavir increases levels of tenofovir DF by decreasing elimination. Use Caution/Monitor.

• terbinafine

  terbinafine will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Assess need to reduce dose of CYP2D6-metabolized drug.
  
  ritonavir will increase the level or effect of terbinafine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tetrabenazine

  ritonavir increases effects of tetrabenazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Decrease tetrabenazine dose by 50% when coadministered with strong CYP2D6 inhibitors.

• tezacaftor

  ritonavir will increase the level or effect of tezacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust tezacaftor dosage regimen if coadministered with a strong CYP3A inhibitor.

• theophylline

  ritonavir will increase the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tiagabine

  ritonavir will increase the level or effect of tiagabine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ticagrelor

  ritonavir increases levels of ticagrelor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ticagrelor is metabolized by CYP3A4/5. Avoid use with strong CYP3A inhibitors.

• timolol

  ritonavir increases levels of timolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of hypotension, bradycardia, AV block, and prolonged PR interval. Consider lowering beta blocker dose.

• tinidazole

  ritonavir will increase the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tipranavir

  ritonavir will increase the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of tipranavir with ritonavir is essential to achieve effective tipranavir plasma concentrations (boosted therapy).
  
  ritonavir and tipranavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• tisotumab vedotin

  ritonavir increases levels of tisotumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tisotumab vedotin?s active metabolite (MMAE) is a CYP3A4 substrate. Coadministration with strong CYP3A4 inhibitors may increase unconjugated MMAE systemic exposure and increase risk of adverse effects.

• tobramycin

  ritonavir will increase the level or effect of tobramycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• tolazamide

  ritonavir, tolazamide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of tolazamide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• tolbutamide

  ritonavir, tolbutamide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of tolbutamide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• tolterodine

  ritonavir will increase the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tolvaptan

  ritonavir will increase the level or effect of tolvaptan by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  tolvaptan will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• topiramate

  topiramate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• toremifene

  ritonavir increases levels of toremifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Metabolism of toremifene may be inhibited by drugs known to inhibit CYP3A4 hepatic enzymes.

• tramadol

  ritonavir will increase the level or effect of tramadol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. May require decreased tramadol dose or adjustment of dosing interval; increased risk for serious adverse events including seizures and serotonin syndrome

• trazodone

  ritonavir will increase the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.
  
  trazodone will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• triamcinolone acetonide injectable suspension

  ritonavir will increase the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• triazolam

  ritonavir will increase the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• trimipramine

  ritonavir will increase the level or effect of trimipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tucatinib

  tucatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Consider reducing the dosage of P-gp substrates, where minimal concentration changes may lead to serious or life-threatening toxicities.

• ubrogepant

  ritonavir will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Dose adjustment is recommended with concomitant use of ubrogepant and moderate and weak CYP3A4 inducers. (see Dosage Modifications)

• ulipristal

  ritonavir will increase the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• umeclidinium bromide/vilanterol inhaled

  ritonavir will increase the level or effect of umeclidinium bromide/vilanterol inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Vilanterol is a CYP3A4 substrate; coadministration with potent CYP3A4 inhibitors may increase systemic exposure

• upadacitinib

  ritonavir will increase the level or effect of upadacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Caution if upadacitinib is coadministered with strong CYP3A4 inhibitors.

• valbenazine

  ritonavir will increase the level or effect of valbenazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Consider reducing valbenazine dose based on tolerability if coadministered with a strong CYP2D6 inhibitor.
  
  ritonavir will increase the level or effect of valbenazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce valbenazine dose to 40 mg once daily when coadministered with a strong CYP3A4 inhibitor.

• valsartan

  ritonavir will increase the level or effect of valsartan by Other (see comment). Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic uptake transporter OATP1B1; coadministration with OATP1B1 inhibitors may increase valsartan systemic exposure
  
  ritonavir will increase the level or effect of valsartan by Mechanism: decreasing hepatic clearance. Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic efflux transporter MRP2; coadministration of inhibitors of the efflux transporter may increase the systemic exposure to valsartan

• vardenafil

  ritonavir will increase the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• vemurafenib

  ritonavir increases levels of vemurafenib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  vemurafenib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• venlafaxine

  ritonavir increases levels of venlafaxine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .

• verapamil

  ritonavir will increase the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  verapamil will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• vilanterol/fluticasone furoate inhaled

  ritonavir will increase the level or effect of vilanterol/fluticasone furoate inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Fluticasone furoate and vilanterol are both CYP3A4 substrates; coadministration with potent CYP3A4 inhibitors may increase systemic exposure

• vinblastine

  ritonavir will increase the level or effect of vinblastine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• vincristine

  ritonavir will increase the level or effect of vincristine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• vincristine liposomal

  ritonavir will increase the level or effect of vincristine liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• voclosporin

  voclosporin, ritonavir. Either increases effects of the other by QTc interval. Use Caution/Monitor.

• warfarin

  ritonavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• zafirlukast

  zafirlukast will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• zanubrutinib

  ritonavir will increase the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce zanubrutinib dose when coadministered with a strong CYP3A4 inhibitor. Interrupt dose as recommended for adverse reactions. After discontinuing the CYP3A4 inhibitor, resume previous dose of zanubrutinib. See zanubrutinib Dosage Modifications for precise recommendation.

• zidovudine

  ritonavir and zidovudine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• zileuton

  ritonavir increases levels of zileuton by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .

Minor (72)

• alfentanil

  ritonavir will increase the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• aliskiren

  ritonavir will increase the level or effect of aliskiren by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of aliskiren by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• alosetron

  ritonavir will increase the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alvimopan

  ritonavir will increase the level or effect of alvimopan by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• aripiprazole

  ritonavir will increase the level or effect of aripiprazole by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• armodafinil

  ritonavir will increase the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of armodafinil by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• atazanavir

  ritonavir will increase the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• bosentan

  ritonavir will increase the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• cevimeline

  ritonavir will increase the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• chlorpromazine

  ritonavir will increase the level or effect of chlorpromazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• clarithromycin

  ritonavir will increase the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dapsone

  ritonavir will increase the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dexfenfluramine

  ritonavir will increase the level or effect of dexfenfluramine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextroamphetamine

  ritonavir will increase the level or effect of dextroamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextromethorphan

  ritonavir will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• disopyramide

  ritonavir will increase the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• docetaxel

  ritonavir will increase the level or effect of docetaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• donepezil

  ritonavir will increase the level or effect of donepezil by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dutasteride

  ritonavir will increase the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• efavirenz

  ritonavir will increase the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• encainide

  ritonavir will increase the level or effect of encainide by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• eplerenone

  ritonavir will increase the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• eucalyptus

  ritonavir will increase the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• fesoterodine

  ritonavir will increase the level or effect of fesoterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fexofenadine

  ritonavir will increase the level or effect of fexofenadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• finasteride

  ritonavir will increase the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• fluoxetine

  ritonavir will increase the level or effect of fluoxetine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fluphenazine

  ritonavir will increase the level or effect of fluphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• food

  food increases levels of ritonavir by enhancing GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• galantamine

  ritonavir will increase the level or effect of galantamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ganaxolone

  ritonavir, ganaxolone. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. Changes in ganaxolone exposures when coadministered with strong, moderate, or weak CYP3A4 inhibitors are not expected to be clinically significant.

• imatinib

  ritonavir will increase the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• isradipine

  ritonavir will increase the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ixazomib

  ritonavir, ixazomib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. In clinical trials, coadministration of ixazomib with strong CYP3A inhibitors did not result in a clinically meaningful change in the systemic exposure of ixazomib.

• ketoconazole

  ritonavir will increase the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• lansoprazole

  ritonavir will increase the level or effect of lansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• levoketoconazole

  ritonavir will increase the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• loratadine

  ritonavir will increase the level or effect of loratadine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of loratadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• mefloquine

  mefloquine decreases levels of ritonavir by unknown mechanism. Minor/Significance Unknown.

• meperidine

  ritonavir decreases levels of meperidine by increasing metabolism. Minor/Significance Unknown. Ritonavir induces the metabolism of meperidine to normeperidine, increasing CNS toxicity.

• montelukast

  ritonavir will increase the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nifedipine

  ritonavir will increase the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nimodipine

  ritonavir will increase the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nitrendipine

  ritonavir will increase the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• oxybutynin

  ritonavir will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paclitaxel

  ritonavir will increase the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paclitaxel protein bound

  ritonavir will increase the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• parecoxib

  ritonavir will increase the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• perhexiline

  ritonavir will increase the level or effect of perhexiline by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• perphenazine

  ritonavir will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• pimozide

  ritonavir will increase the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pioglitazone

  ritonavir will increase the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• prochlorperazine

  ritonavir will increase the level or effect of prochlorperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promazine

  ritonavir will increase the level or effect of promazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promethazine

  ritonavir will increase the level or effect of promethazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• propafenone

  ritonavir will increase the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• rabeprazole

  ritonavir will increase the level or effect of rabeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ramelteon

  ritonavir will increase the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• risperidone

  ritonavir will increase the level or effect of risperidone by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• selexipag

  ritonavir will increase the level or effect of selexipag by decreasing metabolism. Minor/Significance Unknown. Coadministration of selexipag with ritonavir may result in an increase in exposure to selexipag. Despite this pharmacokinetic change, this interaction is likely of little clinical significance

• sufentanil

  ritonavir will increase the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• tolterodine

  ritonavir will increase the level or effect of tolterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• trifluoperazine

  ritonavir will increase the level or effect of trifluoperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• tropisetron

  ritonavir will increase the level or effect of tropisetron by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• vinblastine

  ritonavir will increase the level or effect of vinblastine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• vincristine

  ritonavir will increase the level or effect of vincristine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• vincristine liposomal

  ritonavir will increase the level or effect of vincristine liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• vinorelbine

  ritonavir will increase the level or effect of vinorelbine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zaleplon

  ritonavir will increase the level or effect of zaleplon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ziprasidone

  ritonavir will increase the level or effect of ziprasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zolpidem

  ritonavir will increase the level or effect of zolpidem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zonisamide

  ritonavir will increase the level or effect of zonisamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• abacavir

  Monitor Closely (1)ritonavir and abacavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• abametapir

  Serious - Use Alternative (1)abametapir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. For 2 weeks after abametapir application, avoid taking drugs that are CYP3A4 substrates. If not feasible, avoid use of abametapir.

• abemaciclib

  Monitor Closely (1)ritonavir will increase the level or effect of abemaciclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong CYP3A4 inhibitors increase plasma levels of abemaciclib and its metabolites. Abemaciclib dose reduction required. If a strong CYP3A4 inhibitor is discontinued, increase abemaciclib to the dose prior to initiating the strong inhibitor.

• acalabrutinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of acalabrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of acalabrutinib with strong CYP3A inhibitors. If a strong CYP3A inhibitor must be used short-term (eg, up to 7 days), temporarily interrupt treatment with acalabrutinib.

• acarbose

  Monitor Closely (1)ritonavir decreases effects of acarbose by pharmacodynamic antagonism. Use Caution/Monitor. New onset or exacerbation of diabetes mellitus and hyperglycemia have been reported with protease inhibitors.

• ado-trastuzumab emtansine

  Serious - Use Alternative (1)ritonavir increases levels of ado-trastuzumab emtansine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. DM1, the cytotoxic component, is metabolized mainly by CYP3A4; strong CYP3A4 inhibitors may increase DM1 exposure and toxicity.

• afatinib

  Serious - Use Alternative (1)ritonavir increases levels of afatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Reduce afatinib daily dose by 10 mg if not tolerated when coadministered with P-gp inhibitors.

• albiglutide

  Monitor Closely (1)ritonavir decreases effects of albiglutide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• alfentanil

  Minor (1)ritonavir will increase the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alfuzosin

  Contraindicated (1)ritonavir will increase the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• aliskiren

  Minor (2)ritonavir will increase the level or effect of aliskiren by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of aliskiren by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• almotriptan

  Monitor Closely (1)ritonavir will increase the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• alosetron

  Minor (1)ritonavir will increase the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alprazolam

  Monitor Closely (1)ritonavir will increase the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• alvimopan

  Minor (1)ritonavir will increase the level or effect of alvimopan by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• amikacin

  Monitor Closely (1)ritonavir will increase the level or effect of amikacin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• amiodarone

  Contraindicated (3)ritonavir will increase the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  amiodarone will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Contraindicated.
  
  ritonavir increases levels of amiodarone by decreasing metabolism. Contraindicated.

• amitriptyline

  Monitor Closely (2)ritonavir will increase the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of amitriptyline by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• amlodipine

  Monitor Closely (1)ritonavir will increase the level or effect of amlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• amobarbital

  Monitor Closely (1)amobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• apalutamide

  Monitor Closely (1)ritonavir will increase the level or effect of apalutamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of apalutamide with strong CYP3A4 or CYP2C8 inhibitors does not require initial dosage modification; however, dose reduction may be needed based on tolerability.Serious - Use Alternative (1)apalutamide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP3A4 inducer, with drugs that are CYP3A4 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered. Adjust dose according to prescribing information if needed.

• apixaban

  Serious - Use Alternative (1)ritonavir will increase the level or effect of apixaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If taking apixaban dose >2.5 mg BID, decrease dose by 50% if coadministered with strong dual inhibitors of CYP3A4 and P-gp; if currently taking apixaban 2.5 mg PO BID, avoid coadministration with strong dual inhibitors of CYP3A4 and P-gp

• aprepitant

  Monitor Closely (1)aprepitant will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• aripiprazole

  Monitor Closely (1)ritonavir will increase the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of aripiprazole by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• armodafinil

  Monitor Closely (1)armodafinil will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (2)ritonavir will increase the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of armodafinil by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• artemether

  Monitor Closely (1)ritonavir, artemether. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ritonavir may increase or decrease levels of artemether.

• artemether/lumefantrine

  Monitor Closely (1)ritonavir, artemether/lumefantrine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ritonavir may increase or decrease levels of lumefantrine.

• artesunate

  Monitor Closely (1)ritonavir will decrease the level or effect of artesunate by increasing metabolism. Use Caution/Monitor. Coadministration may decrease AUC and peak plasma concentration of active artesunate metabolite (DHA). Monitor for decreased efficacy.

• atazanavir

  Monitor Closely (2)atazanavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  atazanavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• atogepant

  Monitor Closely (2)ritonavir will increase the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Recommended atogepant dosage is 10 mg PO qDay when coadministered with strong CYP3A4 inhibitors.
  
  ritonavir will increase the level or effect of atogepant by Other (see comment). Modify Therapy/Monitor Closely. Recommended dosage of atogepant (an OATP1B1 substrate) with concomitant use of OATP inhibitors is 10 mg or 30 mg qDay.

• atomoxetine

  Monitor Closely (1)ritonavir will increase the level or effect of atomoxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• atorvastatin

  Monitor Closely (2)ritonavir will increase the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  atorvastatin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases toxicity of atorvastatin by Other (see comment). Avoid or Use Alternate Drug. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• avanafil

  Serious - Use Alternative (1)ritonavir will increase the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. CYP3A4 inhibitors may reduce avanafil clearance increasing systemic exposure to avanafil; significantly increased levels may result in significant adverse events including severe hypotension, syncope, visual changes, and priapism. Coadministration with strong CYP3A4 is contraindicated.

• avapritinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of avapritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of avapritinib with strong CYP3A4 inhibitors.

• avatrombopag

  Serious - Use Alternative (1)ritonavir will increase the level or effect of avatrombopag by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• axitinib

  Serious - Use Alternative (1)ritonavir increases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration with strong CYP3A4 inhibitors, reduce axitinib dose by 50%.

• azithromycin

  Monitor Closely (1)azithromycin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• bazedoxifene/conjugated estrogens

  Monitor Closely (3)ritonavir will increase the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of bazedoxifene/conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir decreases levels of bazedoxifene/conjugated estrogens by increasing metabolism. Use Caution/Monitor. A reduction in bazedoxifene exposure may be associated with an increase risk of endometrial hyperplasia.

• bedaquiline

  Serious - Use Alternative (1)ritonavir will increase the level or effect of bedaquiline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of bedaquiline with strong CYP3A4 inhibitors for >14 consecutive days, unless the benefit of treatment outweighs the risk

• benzhydrocodone/acetaminophen

  Monitor Closely (2)ritonavir will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone [benzhydrocodone is prodrug of hydrocodone]) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.
  
  ritonavir will increase the level or effect of benzhydrocodone/acetaminophen by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with strong CYP3A4 inhibitors may increase hydrocodone (benzhydrocodone is prodrug of hydrocodone) plasma concentrations and can result in potentially fatal respiratory depression.

• berotralstat

  Monitor Closely (2)berotralstat will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor or titrate P-gp substrate dose if coadministered.
  
  ritonavir increases levels of berotralstat by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Reduced berotralstat dose to 110 mg/day when coadministered with P-gp inhibitors.

• betrixaban

  Monitor Closely (1)ritonavir increases levels of betrixaban by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Decrease betrixaban dose to 80 mg PO once, then 40 mg PO qDay if coadministered with a P-gp inhibitor.

• bexarotene

  Monitor Closely (1)ritonavir will increase the level or effect of bexarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• bortezomib

  Monitor Closely (1)ritonavir will increase the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• bosentan

  Serious - Use Alternative (1)bosentan will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. stop bosentan >36 hours prior to PI initiation and restart 10 days after PI initiation at 62.5 mg once daily or every other day.Minor (1)ritonavir will increase the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• bosutinib

  Monitor Closely (1)bosutinib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir increases levels of bosutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inhibitors increases bosutinib plasma concentration ~5-fold.
  
  ritonavir increases levels of bosutinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• brentuximab vedotin

  Monitor Closely (1)ritonavir increases levels of brentuximab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor patients for adverse reactions. .

• brexpiprazole

  Monitor Closely (2)ritonavir will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer half of the usual brexpiprazole dose when coadministered with strong CYP2D6 inhibitors. If also administered with a strong/moderate CYP3A4 inhibitor, administer a quarter of brexpiprazole dose. NOTE: In MDD clinical trials, brexpiprazole dosage was not adjusted for strong CYP2D6 inhibitors (eg, paroxetine, fluoxetine); thus, CYP considerations are already factored into general dosing recommendations and brexpiprazole may be administered without dosage adjustment in patients with MDD.
  
  ritonavir will increase the level or effect of brexpiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Administer half of the usual brexpiprazole dose when coadministered with strong CYP3A4 inhibitors. If also administered with a strong/moderate CYP2D6 inhibitor, administer a quarter of brexpiprazole dose.

• brigatinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of brigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant use of a strong CYP3A inhibitor cannot be avoided, reduce the brigatinib once daily dose by about 50% (ie, from 180 mg to 90 mg, or from 90 mg to 60 mg). After discontinuation of a strong CYP3A inhibitor, resume the brigatinib dose that was tolerated prior to initiating the strong CYP3A inhibitor.

• bromocriptine

  Monitor Closely (1)ritonavir increases levels of bromocriptine by decreasing metabolism. Use Caution/Monitor. Increased levels possibly due to CYP3A4 inhibition.Serious - Use Alternative (1)ritonavir will increase the level or effect of bromocriptine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• budesonide

  Monitor Closely (3)ritonavir will increase the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  budesonide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of budesonide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• buprenorphine

  Monitor Closely (1)ritonavir increases levels of buprenorphine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity.

• buprenorphine buccal

  Monitor Closely (1)ritonavir increases levels of buprenorphine buccal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity.

• buprenorphine subdermal implant

  Monitor Closely (1)ritonavir will increase the level or effect of buprenorphine subdermal implant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor patients already on buprenorphine subdermal implant who require newly-initiated treatment with CYP3A4 inhibitors for signs and symptoms of overmedication. If the dose of the concomitant CYP3A4 inhibitor cannot be reduced or discontinued, implant removal may be necessary and the patient should then be treated with a buprenorphine dosage form that permits dose adjustments. If a CYP3A4 inhibitor is discontinued in a patient who has been stabilized on buprenorphine, monitor the patient for withdrawal.

• buprenorphine transdermal

  Monitor Closely (1)ritonavir will increase the level or effect of buprenorphine transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• buprenorphine, long-acting injection

  Monitor Closely (1)ritonavir will increase the level or effect of buprenorphine, long-acting injection by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Patients who transfer to buprenorphine long-acting injection from transmucosal buprenorphine coadministered with CYP3A4 inhibitors should be monitored to ensure buprenorphine plasma levels are adequate. Within 2 weeks, if signs and symptoms of buprenorphine toxicity or overdose occur and the concomitant CYP3A4 inhibitor cannot be reduced or discontinued, transition the patient back to a buprenorphine formulation that permits dose adjustments.

• bupropion

  Monitor Closely (1)ritonavir decreases levels of bupropion by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Ritonavir decreases levels of bupropion by inducing CYP2B6. Bupropion levels decreased by 20-80%, increased doses of bupropion may be required .

• buspirone

  Monitor Closely (1)ritonavir will increase the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• butabarbital

  Monitor Closely (1)butabarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• butalbital

  Monitor Closely (1)butalbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cabazitaxel

  Monitor Closely (1)ritonavir increases levels of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Avoid coadministration.

• cabergoline

  Serious - Use Alternative (1)ritonavir increases levels of cabergoline by decreasing metabolism. Contraindicated.

• cabotegravir

  Serious - Use Alternative (1)ritonavir, cabotegravir. Other (see comment). Avoid or Use Alternate Drug. Comment: Cabotegravir plus rilpivirine is a complete regimen. Coadministration with other antiretroviral medications for treating HIV-1 infection is not recommended.

• cabozantinib

  Monitor Closely (1)ritonavir will increase the level or effect of cabozantinib by Other (see comment). Use Caution/Monitor. MRP2 inhibitors increase cabozantinib toxicitySerious - Use Alternative (1)ritonavir will increase the level or effect of cabozantinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of cabozantinib with strong CYP3A4 inhibitors. If a strong CYP3A4 inhibitor is required, decrease cabozantinib dose by 40 mg/day (Cometriq) or by 20 mg/day (Cabometyx). Resume previous dose 2-3 days after strong CYP3A4 inhibitor discontinued.

• calcifediol

  Monitor Closely (1)ritonavir, calcifediol. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. CYP450 inhibitors may inhibit enzymes involved in vitamin D metabolism (CYP24A1 and CYP27B1). This may alter serum levels of calcifediol and decrease the conversion of calcifediol to calcitriol. Dose adjustment of calcifediol may be required, and serum 25­hydroxyvitamin D, intact PTH, and serum calcium concentrations should be closely monitored when initiating or discontinuing a strong CYP3A4 inhibitor.

• calcitriol

  Serious - Use Alternative (1)ritonavir will increase the level or effect of calcitriol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• canagliflozin

  Monitor Closely (1)ritonavir decreases levels of canagliflozin by increasing metabolism. Use Caution/Monitor. Coadministration with potent UGT enzyme inducers: Consider increasing dose to 300 mg qDay if 100 mg/day tolerate and additional glycemic control required (eGFR must be >60 mL/min/1.73 m2 to increase dose); if eGFR <60 mL/min/1.73 m2, consider using a different antihyperglycemic agent.

• cannabidiol

  Monitor Closely (1)ritonavir will increase the level or effect of cannabidiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider reducing the cannabidiol dose when coadministered with a strong CYP3A4 inhibitor.

• capmatinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of capmatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• carbamazepine

  Monitor Closely (1)ritonavir will increase the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor plasma levels when used concomitantlySerious - Use Alternative (1)carbamazepine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• cariprazine

  Monitor Closely (1)ritonavir will increase the level or effect of cariprazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with strong CYP3A4 inhibitors requires cariprazine dose reduction. See Dosage Modification section in drug monograph.

• carvedilol

  Monitor Closely (1)ritonavir will increase the level or effect of carvedilol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• cenobamate

  Monitor Closely (1)cenobamate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase dose of CYP3A4 substrate, as needed, when coadministered with cenobamate.

• ceritinib

  Monitor Closely (1)ritonavir increases levels of ceritinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases levels of ceritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid if possible; if concomitant use is unavoidable, reduce ceritinib dose by ~33%; after discontinuation of strong CYP3A inhibitor, resume at previous dose.

• cetirizine

  Monitor Closely (1)ritonavir increases levels of cetirizine by decreasing metabolism. Use Caution/Monitor.

• cevimeline

  Minor (1)ritonavir will increase the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• chloramphenicol

  Serious - Use Alternative (1)chloramphenicol will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• chlordiazepoxide

  Monitor Closely (1)ritonavir increases levels of chlordiazepoxide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Use alternatives if available. Potential for increased toxicity. Consider lowering benzodiazepine dose.

• chlorpromazine

  Minor (1)ritonavir will increase the level or effect of chlorpromazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• chlorpropamide

  Monitor Closely (1)ritonavir, chlorpropamide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of chlorpropamide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• cholic acid

  Monitor Closely (1)ritonavir increases toxicity of cholic acid by decreasing elimination. Modify Therapy/Monitor Closely. Avoid concomitant use of inhibitors of the bile salt efflux pump (BSEP). May exacerbate accumulation of conjugated bile salts in the liver and result in clinical symptoms. If concomitant use is necessary, monitor serum transaminases and bilirubin.

• ciclesonide inhaled

  Monitor Closely (1)ritonavir increases levels of ciclesonide inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of Cushing's syndrome or adrenal suppression.

• cilostazol

  Monitor Closely (1)ritonavir will increase the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cimetidine

  Serious - Use Alternative (1)cimetidine will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• cinacalcet

  Monitor Closely (1)ritonavir will increase the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• citalopram

  Monitor Closely (1)ritonavir increases levels of citalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased risk of serotonin syndrome. ECG monitoring is recommended, along with drugs that may prolong the QT interval.

• clarithromycin

  Monitor Closely (1)clarithromycin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)clarithromycin will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.Minor (1)ritonavir will increase the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• clomipramine

  Monitor Closely (2)ritonavir will increase the level or effect of clomipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• clonazepam

  Monitor Closely (1)ritonavir increases levels of clonazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Use alternatives if available. Consider lowering benzodiazepine dose.

• clopidogrel

  Monitor Closely (1)ritonavir will decrease the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Inhibition of CYP3A4 will reduce clopidogrel bioactivation

• clotrimazole

  Monitor Closely (1)clotrimazole will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• clozapine

  Monitor Closely (1)ritonavir will increase the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cobicistat

  Contraindicated (1)cobicistat will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Serious - Use Alternative (1)ritonavir will increase the level or effect of cobicistat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• cobimetinib

  Contraindicated (1)ritonavir will increase the level or effect of cobimetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Avoid coadministration with strong CYP3A4 inhibitors with (increases cobimetinib systemic exposure by 6.7-fold).

• cocaine

  Monitor Closely (1)ritonavir will increase the level or effect of cocaine by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor.

• codeine

  Monitor Closely (1)ritonavir will decrease the level or effect of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.

• colchicine

  Serious - Use Alternative (1)ritonavir will increase the level or effect of colchicine by Other (see comment). Avoid or Use Alternate Drug. Colchicine is a P-gp and CYP3A4 substrate. Avoid use with drugs that are both P-gp and strong CYP3A4 inhibitors. If coadministration is necessary, decrease colchicine dose or frequency as recommended in prescribing information. Use of any colchicine product in conjunction with strong CYP3A4 inhibitors is contraindicated in patients with renal or hepatic impairment.

• conivaptan

  Contraindicated (1)ritonavir will increase the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of conivaptan with strong CYP3A4 inhibitors is contraindicated.Monitor Closely (1)conivaptan will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conjugated estrogens

  Monitor Closely (2)ritonavir will increase the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• conjugated estrogens, vaginal

  Monitor Closely (2)ritonavir will increase the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of conjugated estrogens, vaginal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• copanlisib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of copanlisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant use with strong CYP3A inhibitors cannot be avoided, reduce copanlisib dose to 45 mg.

• cortisone

  Monitor Closely (3)ritonavir will increase the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  cortisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of cortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• crizotinib

  Monitor Closely (2)ritonavir increases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use of strong CYP3A inhibitors should be avoided. ECG monitoring is recommended, along with drugs that may prolong the QT interval.
  
  crizotinib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• crofelemer

  Monitor Closely (1)crofelemer increases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Crofelemer has the potential to inhibit CYP3A4 at concentrations expected in the gut; unlikely to inhibit systemically because minimally absorbed.

• cyclophosphamide

  Monitor Closely (2)ritonavir will increase the level or effect of cyclophosphamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of cyclophosphamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor.

• cyclosporine

  Monitor Closely (2)ritonavir will increase the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of cyclosporine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dabigatran

  Monitor Closely (1)ritonavir will increase the level or effect of dabigatran by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Atrial fibrillation: Avoid coadministering dabigatran with P-gp inhibitors if CrCl <30 mL/min. DVT/PE treatment: Avoid coadministering dabigatran with P-gp inhibitors if CrCl <50 mL/min

• dabrafenib

  Serious - Use Alternative (3)ritonavir increases levels of dabrafenib by decreasing metabolism. Avoid or Use Alternate Drug. Strong CYP2C8 inhibitors may increase dabrafenib levels.
  
  ritonavir increases levels of dabrafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  dabrafenib will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• dacomitinib

  Serious - Use Alternative (1)dacomitinib will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid use with CYP2D6 substrates where minimal increases in concentration of the CYP2D6 substrate may lead to serious or life-threatening toxicities.

• dapsone

  Minor (1)ritonavir will increase the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• daridorexant

  Serious - Use Alternative (1)ritonavir will increase the level or effect of daridorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• darifenacin

  Monitor Closely (2)darifenacin will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• darolutamide

  Monitor Closely (1)ritonavir will increase the level or effect of darolutamide by Other (see comment). Modify Therapy/Monitor Closely. Darolutamide is a P-gp and CYP3A4 substrate. Closely monitor for increased adverse reactions and modify dose of darolutamide as needed when coadministered with drugs that are both P-gp and strong or moderate CYP3A4 inhibitors.

• darunavir

  Monitor Closely (2)darunavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  darunavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of darunavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• dasatinib

  Monitor Closely (1)dasatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. May require decreased dasatinib dose or adjustment of dosing interval. Both ritonavir and dasatinib are CYP3A4 inhibitor, however, ritonavir is a strong CYP3A4 inhibitor and more likely to increase dasatinib levels and increase risk for toxicity including prolonged QT interval.

• daunorubicin

  Monitor Closely (1)ritonavir will increase the level or effect of daunorubicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• deferasirox

  Monitor Closely (1)ritonavir decreases levels of deferasirox by Other (see comment). Use Caution/Monitor. Comment: Avoid concomitant use of potent UGT inducers with deferasirox. If co-administration is required then consider increasing initial dose of deferasirox to 30 mg/kg and monitor ferritin levels and clinical response.

• deflazacort

  Monitor Closely (2)ritonavir will increase the level or effect of deflazacort by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of deflazacort by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Decrease deflazacort dose to one-third of the recommended dose if coadministered with moderate or strong CYP3A4 inhibitors.

• desipramine

  Monitor Closely (2)ritonavir will increase the level or effect of desipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of desipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• desvenlafaxine

  Monitor Closely (1)ritonavir increases levels of desvenlafaxine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .

• deutetrabenazine

  Monitor Closely (1)ritonavir will increase the level or effect of deutetrabenazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Strong CYP2D6 inhibitors increase the systemic exposure to the active dihydro-metabolites of deutetrabenazine by approximately 3-fold. Do not exceed 18 mg/dose and 36 mg/day of deutetrabenazine if coadministered with strong CYP2D6 inhibitors.

• dexamethasone

  Monitor Closely (3)ritonavir will increase the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  dexamethasone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of dexamethasone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dexfenfluramine

  Minor (1)ritonavir will increase the level or effect of dexfenfluramine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dexlansoprazole

  Monitor Closely (1)ritonavir will increase the level or effect of dexlansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dextroamphetamine

  Minor (1)ritonavir will increase the level or effect of dextroamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• dextromethorphan

  Minor (1)ritonavir will increase the level or effect of dextromethorphan by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• DHEA, herbal

  Monitor Closely (1)DHEA, herbal will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• diazepam

  Monitor Closely (1)ritonavir increases levels of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Use alternatives if available.

• diazepam intranasal

  Monitor Closely (1)ritonavir will increase the level or effect of diazepam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inhibitors may decrease rate of diazepam elimination, thereby increasing adverse reactions to diazepam.

• diazoxide

  Monitor Closely (1)ritonavir increases effects of diazoxide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• didanosine

  Monitor Closely (2)ritonavir will decrease the level or effect of didanosine by increasing gastric pH. Applies only to oral form of both agents. Use Caution/Monitor. Didanosine should be taken 1 hour prior or 2 hours after administration of lopinavir/ritonavir oral solution.
  
  ritonavir and didanosine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• dienogest/estradiol valerate

  Monitor Closely (1)ritonavir will increase the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Significant changes (increase or decrease) in plasma levels of estrogen and progestin have been seen when HIV protease inhibitors are administered. Monitor for potential adverse effects such as nausea, irregular uterine bleeding, breast tenderness and headache.

• digoxin

  Monitor Closely (3)ritonavir will increase the level or effect of digoxin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Plasma concentrations and pharmacologic effects of digoxin may be increased by ritonavir. Monitor for increased effects of digoxin.
  
  ritonavir increases levels of digoxin by decreasing renal clearance. Use Caution/Monitor.
  
  ritonavir increases levels of digoxin by decreasing hepatic clearance. Use Caution/Monitor.

• dihydroergotamine

  Contraindicated (1)ritonavir will increase the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• dihydroergotamine intranasal

  Contraindicated (1)ritonavir will increase the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• diltiazem

  Monitor Closely (2)diltiazem will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• disopyramide

  Minor (1)ritonavir will increase the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• disulfiram

  Contraindicated (1)disulfiram increases toxicity of ritonavir by aldehyde dehydrogenase inhibition. Contraindicated. Interaction only associated with oral solution, which contains 42% alcohol.

• docetaxel

  Monitor Closely (1)ritonavir will increase the level or effect of docetaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of docetaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dofetilide

  Monitor Closely (1)ritonavir increases levels of dofetilide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Use alternatives if available. Increased risk of QT prolongation and cardiac arrhythmias.

• donepezil

  Minor (2)ritonavir will increase the level or effect of donepezil by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• doravirine

  Monitor Closely (1)ritonavir will increase the level or effect of doravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of doravirine and CYP3A4 inhibitors may increase plasma concentrations and toxicities of doravirine.

• doxepin

  Monitor Closely (1)ritonavir will increase the level or effect of doxepin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• doxepin cream

  Monitor Closely (1)ritonavir will increase the level or effect of doxepin cream by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• doxorubicin

  Monitor Closely (2)ritonavir will increase the level or effect of doxorubicin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of doxorubicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• doxorubicin liposomal

  Monitor Closely (2)ritonavir will increase the level or effect of doxorubicin liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of doxorubicin liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• dronabinol

  Monitor Closely (1)ritonavir will increase the level or effect of dronabinol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dronabinol is a CYP3A4 substrate.

• dronedarone

  Monitor Closely (1)dronedarone will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (2)dronedarone will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• duloxetine

  Monitor Closely (1)ritonavir will increase the level or effect of duloxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• dutasteride

  Minor (1)ritonavir will increase the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• duvelisib

  Monitor Closely (2)ritonavir will increase the level or effect of duvelisib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of duvelisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with a strong CYP3A4 inhibitor increases duvelisib AUC, which may increase the risk of duvelisib toxicities. Reduce duvelisib dose to 15 mg BID when coadministered with a strong CYP3A4 inhibitor.

• edoxaban

  Serious - Use Alternative (1)ritonavir will increase the level or effect of edoxaban by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Dose adjustment may be required with strong P-gp inhibitors. DVT/PE treatment: Decrease dose to 30 mg PO once daily. NVAF: No dose reduction recommended

• efavirenz

  Monitor Closely (2)efavirenz will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir and efavirenz both increase risk of immune reconstitution syndrome. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• elagolix

  Contraindicated (1)ritonavir will increase the level or effect of elagolix by Other (see comment). Contraindicated. Concomitant use of elagolix and strong OATP1B1 inhibitors is contraindicated.Monitor Closely (2)elagolix will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  elagolix decreases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak-to-moderate CYP3A4 inducer. Monitor CYP3A substrates if coadministered. Consider increasing CYP3A substrate dose if needed.Serious - Use Alternative (1)ritonavir will increase the level or effect of elagolix by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• elbasvir/grazoprevir

  Serious - Use Alternative (1)ritonavir will increase the level or effect of elbasvir/grazoprevir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• eletriptan

  Monitor Closely (1)ritonavir will increase the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases levels of eletriptan by decreasing metabolism. Contraindicated. Separate by 72 hours.

• eliglustat

  Contraindicated (2)ritonavir will increase the level or effect of eliglustat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors are contraindicated with eliglustat poor or intermediate metabolizers; reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors
  
  ritonavir increases levels of eliglustat by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. If coadministered with strong or moderate CYP2D6 inhibitors, reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive and intermediate metabolizers; eliglustat is contraindiated if strong or moderate CYP2D6 inhibitors are given concomitantly with strong or moderate CYP3A inhibitors.Monitor Closely (2)eliglustat increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the P-gp substrate and titrate to clinical effect.
  
  eliglustat increases levels of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the concomitant drug and titrate to clinical effect.

• eluxadoline

  Monitor Closely (1)ritonavir increases levels of eluxadoline by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. As a precautionary measure due to incomplete information on the metabolism of eluxadoline, use caution when coadministered with strong CYP2D6 inhibitors.Serious - Use Alternative (1)ritonavir increases levels of eluxadoline by decreasing metabolism. Avoid or Use Alternate Drug. Decrease eluxadoline dose to 75 mg PO BID if coadministered with OATP1B1 inhibitors. .

• elvitegravir

  Monitor Closely (1)ritonavir will increase the level or effect of elvitegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  Contraindicated (2)ritonavir, elvitegravir/cobicistat/emtricitabine/tenofovir DF. Other (see comment). Contraindicated. Comment: Elvitegravir/cobicistat/emtricitabine/tenofovir is a complete regimen for HIV and should not be administered with other antiretrovirals.
  
  ritonavir will increase the level or effect of elvitegravir/cobicistat/emtricitabine/tenofovir DF by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• emtricitabine

  Monitor Closely (1)ritonavir and emtricitabine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• encainide

  Minor (1)ritonavir will increase the level or effect of encainide by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• encorafenib

  Monitor Closely (1)encorafenib, ritonavir. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Encorafenib both inhibits and induces CYP3A4 at clinically relevant plasma concentrations. Coadministration of encorafenib with sensitive CYP3A4 substrates may result in increased toxicity or decreased efficacy of these agents.Serious - Use Alternative (1)ritonavir will increase the level or effect of encorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant use of a strong CYP3A4 inhibitor is unavoidable, reduce encorafenib dose to one-third of the dose (eg, reduce from 450 mg/day to 150 mg/day). After discontinuing the inhibitor for 3-5 elimination half-lives, resume previous encorafenib dose.

• enfortumab vedotin

  Monitor Closely (1)ritonavir increases toxicity of enfortumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Enfortumab vedotin is an antibody-drug conjugate that releases monomethylauristatin E (MMAE) via proteolytic cleavage. MMAE is primarily metabolized by CYP3A4 in vitro. Coadministration with strong CYP3A4 inhibitors may increase free MMAE exposure, which may increase the incidence or severity of toxicities.

• enfuvirtide

  Monitor Closely (1)ritonavir and enfuvirtide both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• entrectinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of strong CYP3A4 inhibitors with entrectinib, a CYP3A4 substrate. If coadministration unavoidable, reduce entrectinib dose to 100 mg/day for patients aged 12 y or older with BSA >1.50m2. Resume previous entrectinib dose after discontinuing strong CYP3A inhibitor for 3-5 elimination half-lives.

• enzalutamide

  Contraindicated (2)ritonavir will increase the level or effect of enzalutamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  enzalutamide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• eplerenone

  Minor (1)ritonavir will increase the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• erdafitinib

  Serious - Use Alternative (2)ritonavir will increase the level or effect of erdafitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration with strong CYP3A4 inhibitors, monitor closely for adverse reactions and consider decreasing dose accordingly. If strong CYP3A4 inhibitor is discontinued, consider increasing erdafitinib dose in the absence of any drug-related toxicities.
  
  erdafitinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If coadministration unavoidable, separate administration by at least 6 hr before or after administration of P-gp substrates with narrow therapeutic index.

• ergoloid mesylates

  Contraindicated (1)ritonavir will increase the level or effect of ergoloid mesylates by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Serious - Use Alternative (1)ritonavir increases levels of ergoloid mesylates by decreasing metabolism. Contraindicated.

• ergonovine

  Contraindicated (1)ritonavir will increase the level or effect of ergonovine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• ergotamine

  Serious - Use Alternative (2)ritonavir will increase the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  ritonavir increases levels of ergotamine by decreasing metabolism. Contraindicated.

• erlotinib

  Monitor Closely (1)ritonavir will increase the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• erythromycin base

  Monitor Closely (1)erythromycin base will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir will increase the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  erythromycin base will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin ethylsuccinate

  Monitor Closely (1)erythromycin ethylsuccinate will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir will increase the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  erythromycin ethylsuccinate will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin lactobionate

  Monitor Closely (1)erythromycin lactobionate will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir will increase the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  erythromycin lactobionate will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin stearate

  Monitor Closely (1)erythromycin stearate will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir will increase the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  erythromycin stearate will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• escitalopram

  Monitor Closely (1)ritonavir increases levels of escitalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of serotonin syndrome.

• eslicarbazepine acetate

  Monitor Closely (1)eslicarbazepine acetate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• esomeprazole

  Monitor Closely (1)ritonavir will increase the level or effect of esomeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estradiol

  Monitor Closely (2)ritonavir will increase the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of estradiol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• estradiol vaginal

  Monitor Closely (1)ritonavir will increase the level or effect of estradiol vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with CYP3A4 inhibitors may increase plasma concentrations of estrogens and toxicities.

• estrogens conjugated synthetic

  Monitor Closely (2)ritonavir will increase the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of estrogens conjugated synthetic by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• estrogens esterified

  Monitor Closely (1)ritonavir will increase the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estropipate

  Monitor Closely (2)ritonavir will increase the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of estropipate by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• eszopiclone

  Monitor Closely (1)ritonavir increases levels of eszopiclone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce eszopiclone starting dose to 1 mg/day.

• ethinylestradiol

  Serious - Use Alternative (2)ritonavir will increase the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir, ethinylestradiol. Other (see comment). Avoid or Use Alternate Drug. Comment: Significant changes (increase or decrease) can occur in estrogen plasma levels. Efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended. .

• ethosuximide

  Monitor Closely (1)ritonavir increases levels of ethosuximide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• etonogestrel

  Monitor Closely (1)ritonavir will increase the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• etoposide

  Monitor Closely (2)ritonavir will increase the level or effect of etoposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of etoposide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• etravirine

  Monitor Closely (1)ritonavir will increase the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (2)etravirine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir, etravirine. Other (see comment). Contraindicated. Comment: Different preparations of ritonavir have varying effects on etravirine, due to alterations in metabolism. The following preparations are contraindicated with etravirine: ritonavir 600 mg bid; tipranavir/ritonavir; fosamprenavir/ritonavir; atazanavir/ritonavir. The following preparation should be co-admin. with caution: lopinavir/ritonavir. The following preparations need no dose adjustment: darunavir/ritonavir; saquinavir/ritonavir.

• eucalyptus

  Minor (1)ritonavir will increase the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• everolimus

  Serious - Use Alternative (2)ritonavir will increase the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  ritonavir will increase the level or effect of everolimus by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

• exenatide injectable solution

  Monitor Closely (1)ritonavir decreases effects of exenatide injectable solution by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• exenatide injectable suspension

  Monitor Closely (1)ritonavir decreases effects of exenatide injectable suspension by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors.

• ezogabine

  Monitor Closely (1)ezogabine, ritonavir. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Slight and transient QT-prolongation observed with ezogabine, particularly when dose titrated to 1200 mg/day. QT interval should be monitored when ezogabine is prescribed with agents known to increase QT interval.

• fedratinib

  Monitor Closely (2)fedratinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP3A4 substrates as necessary.
  
  fedratinib will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP2D6 substrates as necessary.Serious - Use Alternative (2)ritonavir will increase the level or effect of fedratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid fedratinib coadministration with strong CYP3A4 inhibitors, decrease fedratinib dose to 200 mg/day. If CYP3A4 inhibitor discontinued, increase fedratinib dose to 300 mg/day for 2 weeks, and then 400 mg/day thereafter as tolerated.
  
  ritonavir will increase the level or effect of fedratinib by Other (see comment). Avoid or Use Alternate Drug. Avoid coadministration of fedratinib (a CYP3A4 and CYP2C19 substrate) with dual CYP3A4 and CYP2C19 inhibitor. Effect of coadministration of a dual CYP3A4 and CYP2C19 inhibitor with fedratinib has not been studied.

• felbamate

  Serious - Use Alternative (1)ritonavir will increase the level or effect of felbamate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• felodipine

  Monitor Closely (2)ritonavir will increase the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  felodipine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• fentanyl

  Serious - Use Alternative (1)ritonavir will increase the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fentanyl intranasal

  Serious - Use Alternative (1)ritonavir will increase the level or effect of fentanyl intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fentanyl transdermal

  Serious - Use Alternative (1)ritonavir will increase the level or effect of fentanyl transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fentanyl transmucosal

  Serious - Use Alternative (1)ritonavir will increase the level or effect of fentanyl transmucosal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

• fesoterodine

  Monitor Closely (1)ritonavir will increase the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of fesoterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fexinidazole

  Serious - Use Alternative (2)ritonavir will decrease the level or effect of fexinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration, monitor fexinidazole for decreased efficacy owing to decreased plasma concentrations of active M1 and M2 metabolites.
  
  fexinidazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Fexinidazole inhibits CYP3A4. Coadministration may increase risk for adverse effects of CYP3A4 substrates.

• fexofenadine

  Minor (1)ritonavir will increase the level or effect of fexofenadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• finasteride

  Minor (1)ritonavir will increase the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• finerenone

  Contraindicated (1)ritonavir will increase the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• flecainide

  Serious - Use Alternative (2)ritonavir will increase the level or effect of flecainide by affecting hepatic enzyme CYP2D6 metabolism. Contraindicated. Concurrent use of flecainide and ritonavir is contraindicated.
  
  ritonavir increases levels of flecainide by decreasing metabolism. Contraindicated.

• flibanserin

  Contraindicated (1)ritonavir will increase the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of flibanserin with moderate or strong CYP3A4 inhibitors is contraindicated. Severe hypotension or syncope can occur.

• fluconazole

  Monitor Closely (1)fluconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fludrocortisone

  Monitor Closely (3)ritonavir will increase the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  fludrocortisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of fludrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• flunisolide inhaled

  Monitor Closely (1)ritonavir will increase the level or effect of flunisolide inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fluoxetine

  Minor (1)ritonavir will increase the level or effect of fluoxetine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• fluphenazine

  Minor (1)ritonavir will increase the level or effect of fluphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• flurazepam

  Monitor Closely (1)ritonavir increases levels of flurazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Use alternatives if available. Consider lowering benzodiazepine dose.

• fluticasone furoate

  Monitor Closely (1)ritonavir will increase the level or effect of fluticasone furoate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inhibitors may increase fluticasone systemic exposure

• fluticasone inhaled

  Monitor Closely (1)ritonavir will increase the level or effect of fluticasone inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inhibitors may increase fluticasone systemic exposure

• fluticasone intranasal

  Serious - Use Alternative (1)ritonavir will increase the level or effect of fluticasone intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inhibitors may increase systemic corticosteroid adverse effects; monitor for signs/symptoms of high corticosteroid concentrations including Cushing type signs/symptoms.

• fluvastatin

  Monitor Closely (1)ritonavir increases toxicity of fluvastatin by Other (see comment). Use Caution/Monitor. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• fluvoxamine

  Monitor Closely (1)fluvoxamine will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• food

  Minor (1)food increases levels of ritonavir by enhancing GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• fosamprenavir

  Monitor Closely (2)fosamprenavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  fosamprenavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of fosamprenavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• fosphenytoin

  Monitor Closely (2)fosphenytoin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  fosphenytoin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• fostamatinib

  Monitor Closely (2)fostamatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Concomitant use of fostamatinib may increase concentrations of P-gp substrates. Monitor for toxicities of the P-gp substrate drug that may require dosage reduction when given concurrently with fostamatinib.
  
  ritonavir will increase the level or effect of fostamatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong CYP3A4 inhibitors may increase exposure to R406 (fostamatinib major active metabolite). Monitor for toxicities that may require fostamatinib dose reduction.

• galantamine

  Minor (2)ritonavir will increase the level or effect of galantamine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ganaxolone

  Minor (1)ritonavir, ganaxolone. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. Changes in ganaxolone exposures when coadministered with strong, moderate, or weak CYP3A4 inhibitors are not expected to be clinically significant.

• garlic

  Monitor Closely (1)garlic decreases levels of ritonavir by unknown mechanism. Use Caution/Monitor.

• gefitinib

  Monitor Closely (1)ritonavir increases levels of gefitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of strong CYP3A4 inhibitors may increase risk for gefitinib adverse effects.

• gentamicin

  Monitor Closely (1)ritonavir will increase the level or effect of gentamicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• gilteritinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of gilteritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Consider alternatives to any strong CYP3A4 inhibitor when coadministered with gilteritinib. If such a combination cannot be avoided, closely monitor for gilteritinib-related adverse effects. Interrupt and reduce gilteritinib dosage in patients with serious or life-threatening toxicity.

• givosiran

  Serious - Use Alternative (1)givosiran will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP2D6 substrates with givosiran. If unavoidable, decrease the CYP2D6 substrate dosage in accordance with approved product labeling.

• glasdegib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of glasdegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Consider alternate therapies that are not strong CYP3A inhibitors or monitor for increased risk of adverse effects, including QTc interval prolongation.

• glecaprevir/pibrentasvir

  Monitor Closely (1)glecaprevir/pibrentasvir will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of glecaprevir/pibrentasvir by decreasing metabolism. Avoid or Use Alternate Drug. Avoid coadministration of glecaprevir/pibrentasvir with ritonavir (P-gp and a strong CYP3A4 inhibitor).

• glimepiride

  Monitor Closely (1)ritonavir, glimepiride. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of glimepiride. Use alternatives if available. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• glipizide

  Monitor Closely (1)ritonavir, glipizide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of glipizide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• glyburide

  Monitor Closely (1)ritonavir, glyburide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of glyburide. Use alternatives if available. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• grapefruit

  Monitor Closely (1)grapefruit will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• griseofulvin

  Monitor Closely (1)griseofulvin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• guanfacine

  Monitor Closely (1)ritonavir will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

• haloperidol

  Monitor Closely (3)ritonavir will increase the level or effect of haloperidol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of haloperidol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  haloperidol and ritonavir both increase QTc interval. Use Caution/Monitor.

• hydrocodone

  Monitor Closely (2)ritonavir will increase the level or effect of hydrocodone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Hydromorphone (<3% of the circulating parent hydrocodone) is mainly formed by CYP2D6 mediated O-demethylation of hydrocodone. Hydromorphone may contribute to the total analgesic effect of hydrocodone.
  
  ritonavir will increase the level or effect of hydrocodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with CYP3A4 inhibitors may increase hydrocodone plasma concentrations and can result in potentially fatal respiratory depression

• hydrocortisone

  Monitor Closely (3)ritonavir will increase the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  hydrocortisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of hydrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• hydromorphone

  Monitor Closely (1)ritonavir will increase the level or effect of hydromorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• hydroxychloroquine sulfate

  Serious - Use Alternative (1)hydroxychloroquine sulfate and ritonavir both increase QTc interval. Avoid or Use Alternate Drug.

• hydroxyprogesterone caproate

  Monitor Closely (1)ritonavir will increase the level or effect of hydroxyprogesterone caproate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ibrutinib

  Serious - Use Alternative (1)ritonavir increases levels of ibrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of ibrutinib and strong CYP3A4 inhibitors. If a strong CYP3A4 inhibitor must be used short-term (eg, anti-infectives for =7 days), interrupt ibrutinib therapy until strong CYP3A4 inhibitor is discontinued.

• idelalisib

  Serious - Use Alternative (2)ritonavir will increase the level or effect of idelalisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministered with strong CYP3A inhibitors, monitor for signs of idelalisib toxicity; follow recommendations for dosage modifications if adverse reactions occur
  
  idelalisib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Idelalisib is a strong CYP3A inhibitor; avoid coadministration with sensitive CYP3A substrates

• ifosfamide

  Monitor Closely (2)ritonavir will decrease the level or effect of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of CYP3A4 inhibitors may decrease the metabolism of ifosfamide to its active alkylating metabolites and decrease the efficacy of ifosfamide.
  
  ritonavir increases effects of ifosfamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Coadministration of ifosfamide with CYP2B6 inducers may increase metabolism of ifosfamide to its metabolite. Monitor for increased effects/toxicities if combined with CYP2B6 inducers.

• iloperidone

  Monitor Closely (3)ritonavir will increase the level or effect of iloperidone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  iloperidone increases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Iloperidone is a time-dependent CYP3A inhibitor and may lead to increased plasma levels of drugs predominantly eliminated by CYP3A4.

• imatinib

  Monitor Closely (1)ritonavir will increase the level or effect of imatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• imipramine

  Monitor Closely (2)ritonavir will increase the level or effect of imipramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• indacaterol, inhaled

  Monitor Closely (2)indacaterol, inhaled, ritonavir. QTc interval. Use Caution/Monitor. Drugs that are known to prolong the QTc interval may have an increased the risk of ventricular arrhythmias.
  
  ritonavir increases levels of indacaterol, inhaled by Other (see comment). Use Caution/Monitor. Comment: Data suggests that systemic clearance is influenced by modulation of both P-gp and CYP3A4 activities. No dose adjustment is warranted at the 75 mcg dose.

• indinavir

  Monitor Closely (4)indinavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  indinavir will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  indinavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• infigratinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of infigratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• insulin aspart

  Monitor Closely (1)ritonavir decreases effects of insulin aspart by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin degludec

  Monitor Closely (1)ritonavir decreases effects of insulin degludec by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. HIV protease inhibitors may cause new onset diabetes mellitus (DM), exacerbate existing DM, and cause hyperglycemia due to insulin resistance.

• insulin degludec/insulin aspart

  Monitor Closely (1)ritonavir decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. HIV protease inhibitors may cause new onset diabetes mellitus (DM), exacerbate existing DM, and cause hyperglycemia due to insulin resistance.

• insulin detemir

  Monitor Closely (1)ritonavir decreases effects of insulin detemir by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin glargine

  Monitor Closely (1)ritonavir decreases effects of insulin glargine by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin glulisine

  Monitor Closely (1)ritonavir decreases effects of insulin glulisine by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin inhaled

  Monitor Closely (1)ritonavir decreases effects of insulin inhaled by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. HIV protease inhibitors may cause new onset diabetes mellitus (DM), exacerbate existing DM, and cause hyperglycemia due to insulin resistance.

• insulin lispro

  Monitor Closely (1)ritonavir decreases effects of insulin lispro by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin NPH

  Monitor Closely (1)ritonavir decreases effects of insulin NPH by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• insulin regular human

  Monitor Closely (1)ritonavir decreases effects of insulin regular human by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• irinotecan

  Contraindicated (1)ritonavir will increase the level or effect of irinotecan by P-glycoprotein (MDR1) efflux transporter. Contraindicated.Serious - Use Alternative (1)ritonavir will increase the level or effect of irinotecan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• irinotecan liposomal

  Contraindicated (1)ritonavir will increase the level or effect of irinotecan liposomal by P-glycoprotein (MDR1) efflux transporter. Contraindicated.Serious - Use Alternative (1)ritonavir will increase the level or effect of irinotecan liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• isavuconazonium sulfate

  Monitor Closely (1)ritonavir will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• isoniazid

  Monitor Closely (1)isoniazid will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• isradipine

  Minor (1)ritonavir will increase the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• istradefylline

  Monitor Closely (3)istradefylline will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of CYP3A4 substrates in clinical trials. This effect was not observed with istradefylline 20 mg/day. Consider dose reduction of sensitive CYP3A4 substrates.
  
  istradefylline will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of P-gp substrates in clinical trials. Consider dose reduction of sensitive P-gp substrates.
  
  ritonavir will increase the level or effect of istradefylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Do not exceed istradefylline 20 mg/day if coadministered with strong CYP3A4 inhibitors.

• itraconazole

  Monitor Closely (1)ritonavir will increase the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Limit itraconazole dose to 200 mg/day in patients receiving ritonavir.

• ivabradine

  Contraindicated (1)ritonavir will increase the level or effect of ivabradine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of ivabradine with strong CYP3A4 inhibitors is contraindicated.

• ivacaftor

  Monitor Closely (2)ivacaftor increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Ivacaftor and its M1 metabolite has the potential to inhibit P-gp; may significantly increase systemic exposure to sensitive P-gp substrates with a narrow therapeutic index.
  
  ritonavir will increase the level or effect of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce ivacaftor dose if coadministered with strong CYP3A4 inhibitors. See specific ivacaftor-containing product for precise dosage modification.

• ivermectin

  Monitor Closely (1)ritonavir will increase the level or effect of ivermectin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• ivosidenib

  Serious - Use Alternative (2)ritonavir will increase the level or effect of ivosidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of strong CYP3A4 inhibitors with ivosidenib or replace with alternate therapies. If coadministration of a strong CYP3A4 inhibitor is unavoidable, reduce ivosidenib dose to 250 mg qDay. If the strong inhibitor is discontinued, increase ivosidenib dose (after at least 5 half-lives of the strong CYP3A4 inhibitor) to the recommended dose of 500 mg qDay. Monitor for increased risk of QTc interval prolongation.
  
  ivosidenib will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP3A4 substrates with ivosidenib or replace with alternative therapies. If coadministration is unavoidable, monitor patients for loss of therapeutic effect of these drugs.

• ixabepilone

  Monitor Closely (1)ritonavir will increase the level or effect of ixabepilone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ixazomib

  Minor (1)ritonavir, ixazomib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. In clinical trials, coadministration of ixazomib with strong CYP3A inhibitors did not result in a clinically meaningful change in the systemic exposure of ixazomib.

• ketamine

  Monitor Closely (1)ritonavir will decrease the level or effect of ketamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ketoconazole

  Monitor Closely (2)ketoconazole will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ketoconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ketoconazole dose is not to exceed 200 mg/day when concurrently used with ritonavir. Minor (1)ritonavir will increase the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• lacosamide

  Monitor Closely (2)ritonavir increases levels of lacosamide by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Potential for increased toxicity. Use alternatives if available. Increased risk of PR prolongation and cardiac arrhythmias.
  
  ritonavir, lacosamide. Either increases levels of the other by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider decreasing lacosamide dose when coadministered with strong CYP3A4 inhibitors.

• lamivudine

  Monitor Closely (1)ritonavir and lamivudine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• lamotrigine

  Monitor Closely (1)ritonavir will decrease the level or effect of lamotrigine by increasing metabolism. Use Caution/Monitor. Combination may decrease lamotrigine levels by 50%. Adjust lamotrigine dose as needed when starting, stopping, or changing ritonavir dose. Similar interactions are possible with other RTV-boosted PIs.

• lansoprazole

  Minor (1)ritonavir will increase the level or effect of lansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• lapatinib

  Monitor Closely (2)lapatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  lapatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• larotrectinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of larotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of larotrectinib with strong CYP3A4 inhibitors is unavoidable, reduce larotrectinib dose by 50%. Resume prior larotrectinib dose once CYP3A4 inhibitor discontinued for 3-5 half-lives.

• lasmiditan

  Serious - Use Alternative (1)lasmiditan increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• lefamulin

  Serious - Use Alternative (1)ritonavir will increase the level or effect of lefamulin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lefamulin with strong CYP3A inhibitors.

• lemborexant

  Serious - Use Alternative (1)ritonavir will increase the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lemborexant with moderate or strong CYP3A inhibitors.

• letermovir

  Monitor Closely (2)ritonavir increases levels of letermovir by decreasing metabolism. Use Caution/Monitor. Coadminstration of letermovir, an OATP1B1/3 substrate, with OATP1B1/3 inhibitors may increase letermovir plasma concentrations.
  
  letermovir increases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levamlodipine

  Monitor Closely (1)ritonavir will increase the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levocetirizine

  Monitor Closely (1)ritonavir increases levels of levocetirizine by decreasing metabolism. Use Caution/Monitor.

• levoketoconazole

  Monitor Closely (2)levoketoconazole will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  levoketoconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ketoconazole dose is not to exceed 200 mg/day when concurrently used with ritonavir. Minor (1)ritonavir will increase the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• levomilnacipran

  Monitor Closely (1)ritonavir will increase the level or effect of levomilnacipran by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Do not exceed 80 mg/day of levomilnacipran when coadministered with strong CYP3A4 inhibitors

• levonorgestrel intrauterine

  Serious - Use Alternative (1)ritonavir will increase the level or effect of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• levonorgestrel oral

  Serious - Use Alternative (1)ritonavir will increase the level or effect of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate

  Serious - Use Alternative (1)ritonavir, levonorgestrel oral/ethinylestradiol/ferrous bisglycinate. Other (see comment). Avoid or Use Alternate Drug. Comment: Significant changes (increase or decrease) can occur in estrogen plasma levels. Efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.

• linagliptin

  Monitor Closely (2)ritonavir increases levels of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .
  
  ritonavir decreases effects of linagliptin by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• liraglutide

  Monitor Closely (1)ritonavir decreases effects of liraglutide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• lofepramine

  Monitor Closely (1)ritonavir will increase the level or effect of lofepramine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• lofexidine

  Monitor Closely (1)ritonavir will increase the level or effect of lofexidine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Concomitant use of lofexidine with strong CYP2D6 inhibitors may increase lofexidine plasma levels. Monitor for symptoms of orthostasis and bradycardia if coadministered with a CYP2D6 inhibitor. Consider lofexidine dose reduction.

• lomitapide

  Contraindicated (1)ritonavir increases levels of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Increases lomitapide levels several folds.Monitor Closely (1)lomitapide increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Consider reducing dose when used concomitantly with lomitapide.

• lonafarnib

  Contraindicated (1)ritonavir will increase the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Lonafarnib is a sensitive CYP3A4 substrate. Coadministration with strong or moderate CYP3A4 inhibitors is contraindicated.

• loperamide

  Monitor Closely (1)ritonavir will increase the level or effect of loperamide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• lopinavir

  Monitor Closely (1)ritonavir will increase the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• loratadine

  Monitor Closely (2)ritonavir will increase the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  loratadine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (2)ritonavir will increase the level or effect of loratadine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.
  
  ritonavir will increase the level or effect of loratadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

• lorcaserin

  Monitor Closely (1)lorcaserin will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• lorlatinib

  Serious - Use Alternative (2)lorlatinib will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of lorlatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministering lorlatinib with strong CYP3A inhibitors. If unavoidable, reduce lorlatinib dose by 25 mg/day. If strong CYP3A inhibitor discontinued, increase to previous lorlatinib (dose after 3 plasma half-lives of strong CYP3A inhibitor). See monograph for further details.

• losartan

  Monitor Closely (1)ritonavir will increase the level or effect of losartan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lovastatin

  Contraindicated (2)ritonavir will increase the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors increase systemic statin exposure and risk of myopathy, including rhabdomyolysis
  
  lovastatin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

• lumacaftor/ivacaftor

  Monitor Closely (1)ritonavir increases levels of lumacaftor/ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong CYP3A inhibitors do not impact lumacaftor exposure, but increased ivacaftor exposure by 4.3-fold. Due to the induction effect of lumacaftor on CYP3A, at steady-state the net exposure of ivacaftor is not expected to exceed that when given in the absence of lumacaftor at a dose of 150 mg q12hr (the approved dose of ivacaftor monotherapy). Therefore, no dose adjustment is necessary when CYP3A inhibitors are initiated in patients currently taking lumacaftor/ivacaftor. However, when initiating lumacaftor/ivacaftor in patients taking strong CYP3A inhibitors, reduce the dose to 1 tablet daily (lumacaftor 200 mg/ivacaftor 125 mg total daily dose) for the first week of treatment to allow for the steady-state induction effect of lumacaftor. Following this period, continue with the recommended daily dose. No dose adjustment is required for moderate or weak CYP3A4 inhibitors.

• lumateperone

  Monitor Closely (1)ritonavir will increase the level or effect of lumateperone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce lumateperone dose to 10.5 mg/day if coadministered with strong CYP3A4 inhibitors.

• lumefantrine

  Monitor Closely (1)ritonavir, lumefantrine. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ritonavir may increase or decrease levels of lumefantrine.

• lurasidone

  Contraindicated (1)ritonavir will increase the level or effect of lurasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of lurasidone and strong CYP3A4 inhibitors is contraindicated.

• lurbinectedin

  Serious - Use Alternative (1)ritonavir will increase the level or effect of lurbinectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• macitentan

  Serious - Use Alternative (1)ritonavir will increase the level or effect of macitentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministering macitentan with strong CYP3A4 inhibitors

• maraviroc

  Monitor Closely (2)ritonavir will increase the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Decrease maraviroc dose to 150 mg BID when coadministered with strong CYP3A4 inhibitors
  
  ritonavir will increase the level or effect of maraviroc by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• marijuana

  Monitor Closely (2)marijuana will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of marijuana by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• mavacamten

  Contraindicated (1)ritonavir will increase the level or effect of mavacamten by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors may increase mavacamten systemic exposure, resulting in heart failure due to systolic dysfunction.

• medroxyprogesterone

  Serious - Use Alternative (1)ritonavir will increase the level or effect of medroxyprogesterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• mefloquine

  Serious - Use Alternative (2)ritonavir increases levels of mefloquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Potential for increased toxicity. Avoid coadministration during and for 15 weeks after discontinuing mefloquine. .
  
  ritonavir increases toxicity of mefloquine by QTc interval. Avoid or Use Alternate Drug.Minor (1)mefloquine decreases levels of ritonavir by unknown mechanism. Minor/Significance Unknown.

• meperidine

  Monitor Closely (1)ritonavir increases levels of meperidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.Minor (1)ritonavir decreases levels of meperidine by increasing metabolism. Minor/Significance Unknown. Ritonavir induces the metabolism of meperidine to normeperidine, increasing CNS toxicity.

• mestranol

  Monitor Closely (3)ritonavir will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir decreases levels of mestranol by increasing metabolism. Use Caution/Monitor. May result in contraceptive failure; use additional or alternative method.

• metformin

  Monitor Closely (1)ritonavir decreases effects of metformin by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• methadone

  Monitor Closely (2)ritonavir will increase the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir decreases effects of methadone by Other (see comment). Use Caution/Monitor. Comment: Ritonavir may induce the metabolism of methadone and/or induce the p glycoprotein pathway that pumps drugs out of the CNS.

• methamphetamine

  Monitor Closely (1)ritonavir will increase the level or effect of methamphetamine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• methylergonovine

  Contraindicated (1)ritonavir will increase the level or effect of methylergonovine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Serious - Use Alternative (1)ritonavir increases levels of methylergonovine by decreasing metabolism. Contraindicated.

• methylprednisolone

  Monitor Closely (3)ritonavir will increase the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  methylprednisolone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of methylprednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• metoclopramide intranasal

  Serious - Use Alternative (1)ritonavir will increase the level or effect of metoclopramide intranasal by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of metoclopramide intranasal and strong CYP2D6 inhibitors is not recommended since the metoclopramide intranasal dose cannot be adjusted.

• metoprolol

  Monitor Closely (1)ritonavir will increase the level or effect of metoprolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• metronidazole

  Monitor Closely (1)metronidazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• mexiletine

  Monitor Closely (1)ritonavir will increase the level or effect of mexiletine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Monitor patients for signs and symptoms of mexiletine toxicity (nausea, dizziness, cardiac arrhythmias). Therapeutic concentration monitoring is recommended for mexiletine, if available. Reduce doses of mexiletine as required.

• miconazole vaginal

  Monitor Closely (1)miconazole vaginal will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• midazolam

  Monitor Closely (1)ritonavir will increase the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases levels of midazolam by decreasing metabolism. Contraindicated.

• midazolam intranasal

  Serious - Use Alternative (1)ritonavir will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of strong CYP3A4 inhibitors with midazolam intranasal causes higher midazolam systemic exposure, which may prolong sedation.

• midostaurin

  Serious - Use Alternative (1)ritonavir will increase the level or effect of midostaurin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong CYP3A4 inhibitors cannot be avoided, monitor midostaurin for increased risk of adverse reactions, especially during the first week of treatment.

• mifepristone

  Monitor Closely (3)ritonavir will increase the level or effect of mifepristone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Do not exceed mifepristone 300 mg/day for Cushing syndrome when coadministered with strong CYP3A4 inhibitors
  
  mifepristone, ritonavir. QTc interval. Modify Therapy/Monitor Closely. Use alternatives if available.
  
  mifepristone will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• miglitol

  Monitor Closely (1)ritonavir decreases effects of miglitol by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• mipomersen

  Monitor Closely (1)mipomersen, ritonavir. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Both drugs have potential to increase hepatic enzymes; monitor LFTs.

• mirabegron

  Monitor Closely (1)mirabegron will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• mirtazapine

  Monitor Closely (1)ritonavir increases levels of mirtazapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• mitotane

  Monitor Closely (1)mitotane decreases levels of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Mitotane is a strong inducer of cytochrome P-4503A4; monitor when coadministered with CYP3A4 substrates for possible dosage adjustments.

• mobocertinib

  Serious - Use Alternative (2)ritonavir will increase the level or effect of mobocertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  mobocertinib and ritonavir both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.

• modafinil

  Serious - Use Alternative (1)ritonavir will increase the level or effect of modafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• mometasone inhaled

  Monitor Closely (1)ritonavir increases levels of mometasone inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of Cushing's syndrome or adrenal suppression.

• mometasone, intranasal

  Monitor Closely (1)ritonavir will increase the level or effect of mometasone, intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• montelukast

  Minor (1)ritonavir will increase the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• morphine

  Monitor Closely (1)ritonavir will increase the level or effect of morphine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• nafcillin

  Monitor Closely (1)nafcillin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• naldemedine

  Monitor Closely (2)ritonavir increases levels of naldemedine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor naldemedine for potential adverse effects if coadministered with strong or moderate CYP3A4 inhibitors.
  
  ritonavir increases levels of naldemedine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor naldemedine for potential adverse effects if coadministered with P-gp inhibitors.

• naloxegol

  Contraindicated (1)ritonavir will increase the level or effect of naloxegol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of naloxegol with strong CYP3A4 inhibitors can significantly increase naloxegol systemic exposure which may precipitate opioid withdrawal symptoms

• nateglinide

  Monitor Closely (1)ritonavir decreases effects of nateglinide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• nebivolol

  Monitor Closely (1)ritonavir will increase the level or effect of nebivolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• nefazodone

  Monitor Closely (2)nefazodone will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nefazodone will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of nefazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• nelfinavir

  Monitor Closely (4)nelfinavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of nelfinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  nelfinavir and ritonavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• neomycin PO

  Monitor Closely (1)ritonavir will increase the level or effect of neomycin PO by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• neratinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of neratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of neratinib with strong/moderate CYP3A4 inhibitors.

• netupitant/palonosetron

  Monitor Closely (1)ritonavir will increase the level or effect of netupitant/palonosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Netupitant is mainly metabolized by CYP3A4; no dosage adjustment is required

• nevirapine

  Monitor Closely (3)nevirapine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of nevirapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir and nevirapine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• nicardipine

  Monitor Closely (2)ritonavir will increase the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nicardipine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• nifedipine

  Monitor Closely (2)nifedipine will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nifedipine will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nilotinib

  Monitor Closely (2)nilotinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  nilotinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. May require decreased nilotinib dose or adjustment of dosing interval. Both ritonavir and nilotinib are CYP3A4 inhibitor, however, ritonavir is a strong CYP3A4 inhibitor and more likely to increase nilotinib levels and increase risk for toxicity including prolonged QT interval

• nimodipine

  Minor (1)ritonavir will increase the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nintedanib

  Monitor Closely (1)ritonavir increases levels of nintedanib by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. If nintedanib adverse effects occur, management may require interruption, dose reduction, or discontinuation of therapy .

• nisoldipine

  Monitor Closely (1)ritonavir will increase the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nitrendipine

  Minor (1)ritonavir will increase the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• norethindrone

  Monitor Closely (1)ritonavir will increase the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• norgestrel

  Serious - Use Alternative (1)ritonavir will increase the level or effect of norgestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• nortriptyline

  Monitor Closely (1)ritonavir will increase the level or effect of nortriptyline by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• olanzapine

  Monitor Closely (1)ritonavir decreases levels of olanzapine by increasing metabolism. Use Caution/Monitor.

• olaparib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of olaparib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong CYP3A inhibitors cannot be avoided, reduce olaparib dose to 150 mg (capsule) or 100 mg (tablet) PO BID. Do not substitute tablets with capsules.

• oliceridine

  Monitor Closely (2)ritonavir will increase the level or effect of oliceridine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.
  
  ritonavir will increase the level or effect of oliceridine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.

• olodaterol inhaled

  Monitor Closely (1)ritonavir and olodaterol inhaled both increase QTc interval. Use Caution/Monitor. Drugs that prolong the QTc interval and may potentiate the effects of beta2 agonists on the cardiovascular system; increased risk of ventricular arrhythmias

• ombitasvir/paritaprevir/ritonavir

  Serious - Use Alternative (1)ritonavir will increase the level or effect of ombitasvir/paritaprevir/ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC)

  Serious - Use Alternative (1)ritonavir will increase the level or effect of ombitasvir/paritaprevir/ritonavir & dasabuvir (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• omeprazole

  Monitor Closely (1)ritonavir will increase the level or effect of omeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ondansetron

  Monitor Closely (2)ritonavir and ondansetron both increase QTc interval. Use Caution/Monitor. Avoid with congenital long QT syndrome; ECG monitoring recommended with concomitant medications that prolong QT interval, electrolyte abnormalities, CHF, or bradyarrhythmias. May increase ondansetron levels.
  
  ritonavir will increase the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• orlistat

  Monitor Closely (1)orlistat will decrease the level or effect of ritonavir by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Loss of virological control reported in HIV-infected patients taking orlistat concomitantly. Exact mechanism is unclear, but may include a drug-drug interaction that inhibits systemic absorption of the antiretroviral drug. Monitor HIV RNA levels frequently and if increased HIV viral load confirmed, discontinue orlistat.

• osilodrostat

  Monitor Closely (1)ritonavir will increase the level or effect of osilodrostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce dose of osilodrostat, a CYP3A4 substrate, by half when coadministered with a strong CYP3A4 inhibitor.

• osimertinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of osimertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of osimertinib with strong CYP3A4 inhibitors. If no other alternative treatment exists, monitor patient more closely for adverse effects.

• ospemifene

  Monitor Closely (1)ritonavir increases levels of ospemifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• oxcarbazepine

  Monitor Closely (1)oxcarbazepine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• oxybutynin

  Minor (1)ritonavir will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• oxycodone

  Serious - Use Alternative (2)ritonavir increases levels of oxycodone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Oxycodone dose reduction may be warranted when coadministered with strong CYP3A4 inhibitors.
  
  ritonavir increases levels of oxycodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Oxycodone dose reduction may be warranted when coadministered with strong CYP3A4 inhibitors.

• oxymorphone

  Monitor Closely (1)ritonavir will increase the level or effect of oxymorphone by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• ozanimod

  Monitor Closely (2)ritonavir will increase the level or effect of ozanimod by Other (see comment). Modify Therapy/Monitor Closely. Coadministration of ozanimod (a CYP2C8 substrate) with strong CYP2C8 inhibitors increases the exposure of the active metabolites (CC112273 and CC1084037) of ozanimod, which may increase the risk of ozanimod adverse reactions. Therefore, coadministration of ozanimod with strong CYP2C8 inhibitors is not recommended.
  
  ozanimod and ritonavir both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties.

• paclitaxel

  Monitor Closely (2)ritonavir will increase the level or effect of paclitaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of paclitaxel by Other (see comment). Modify Therapy/Monitor Closely. Paclitaxel levels/toxicity may increase when coadministered with CYP2C8 inhibitorsMinor (1)ritonavir will increase the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paclitaxel protein bound

  Monitor Closely (2)ritonavir will increase the level or effect of paclitaxel protein bound by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of paclitaxel protein bound by Other (see comment). Modify Therapy/Monitor Closely. Paclitaxel levels/toxicity may increase when coadministered with CYP2C8 inhibitorsMinor (1)ritonavir will increase the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pacritinib

  Serious - Use Alternative (1)ritonavir will decrease the level or effect of pacritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• palbociclib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of palbociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of palbociclib with strong CYP3A inhibitors. If unable to avoid, reduce palbociclib dose to 75 mg/day.

• paliperidone

  Monitor Closely (1)ritonavir will increase the level or effect of paliperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• panobinostat

  Monitor Closely (1)ritonavir increases levels of panobinostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce panobinostat starting dose to 10 mg if coadministered with strong CYP3A4 inhibitors.

• parecoxib

  Minor (1)ritonavir will increase the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paricalcitol

  Monitor Closely (1)ritonavir increases levels of paricalcitol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity.

• paromomycin

  Monitor Closely (1)ritonavir will increase the level or effect of paromomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• paroxetine

  Monitor Closely (1)ritonavir will increase the level or effect of paroxetine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• pazopanib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of pazopanib with strong CYP3A4 inhibitors if possible; if must coadminister, decrease pazopanib dose to 400 mg/day

• peginterferon alfa 2b

  Monitor Closely (1)peginterferon alfa 2b, ritonavir. Other (see comment). Use Caution/Monitor. Comment: When patients are administered peginterferon alpha-2b with CYP2D6 substrates, the therapeutic effect of these drugs may be altered. Peginterferon alpha-2b may increase or decrease levels of CYP2D6 substrate. The concomitant use of interferons and anti-retroviral protease inhibitors should be done with caution as both can cause hepatic damage. .

• pemigatinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of pemigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors is unavoidable, reduce pemigatinib dose (refer to drug monograph dosage modifications). After discontinuing the CYP3A4 inhibitor for 3 elimination half-lives, may resume previous pemigatinib dose.

• pentobarbital

  Monitor Closely (1)pentobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• perampanel

  Monitor Closely (1)ritonavir will increase the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• perhexiline

  Minor (1)ritonavir will increase the level or effect of perhexiline by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• perphenazine

  Minor (1)ritonavir will increase the level or effect of perphenazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• pexidartinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of pexidartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors is unavoidable, reduce pexidartinib dose (refer to drug monograph dosage modifications). After discontinuing the CYP3A4 inhibitor for 3 elimination half-lives, may resume previous pexidartinib dose.

• phenobarbital

  Monitor Closely (2)phenobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  phenobarbital will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• phenytoin

  Monitor Closely (2)phenytoin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  phenytoin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• pimavanserin

  Serious - Use Alternative (1)ritonavir will increase the level or effect of pimavanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Decrease dose to 17 mg/day if pimavanserin is coadministered with strong CYP3A4 inhibitors.

• pimozide

  Contraindicated (1)ritonavir increases levels of pimozide by decreasing metabolism. Contraindicated. Risk of QT interval prolongation.Minor (1)ritonavir will increase the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pioglitazone

  Minor (1)ritonavir will increase the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pitavastatin

  Monitor Closely (1)ritonavir increases toxicity of pitavastatin by Other (see comment). Use Caution/Monitor. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• pitolisant

  Monitor Closely (1)ritonavir will increase the level or effect of pitolisant by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. If coadministered with strong CYP2D6 inhibitors, initiate pitolisant at 8.9 mg/day and increase after 7 days to maximum of 17.8 mg/day. For patients currently taking pitolisant, reduce pitolisant dose by half upon initiating strong CYP2D6 inhibitors.

• polatuzumab vedotin

  Monitor Closely (1)ritonavir will increase the level or effect of polatuzumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Polatuzumab undergoes catabolism to small peptides, amino acids, monomethyl auristatin E (MMAE), and unconjugated MMAE-related catabolites. MMAE is a CYP3A4 substrate. Coadministration of polatuzumab vedotin with a strong CYP3A4 inhibitor may increase unconjugated MMAE AUC, which may increase polatuzumab vedotin toxicities.

• pomalidomide

  Serious - Use Alternative (2)ritonavir increases levels of pomalidomide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir increases levels of pomalidomide by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• ponatinib

  Monitor Closely (1)ponatinib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases levels of ponatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Decrease ponatinib starting dose to 30 mg qDay if coadministration with strong CYP3A4 inhibitors cannot be avoided.

• posaconazole

  Monitor Closely (2)posaconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of posaconazole by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• pralsetinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of pralsetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• pramlintide

  Monitor Closely (1)ritonavir decreases effects of pramlintide by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• pravastatin

  Monitor Closely (1)ritonavir increases toxicity of pravastatin by Other (see comment). Use Caution/Monitor. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• praziquantel

  Monitor Closely (1)ritonavir will increase the level or effect of praziquantel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• prednisolone

  Monitor Closely (2)ritonavir will increase the level or effect of prednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of prednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• prednisone

  Monitor Closely (3)ritonavir will increase the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  prednisone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of prednisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• primidone

  Monitor Closely (1)primidone will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• prochlorperazine

  Minor (1)ritonavir will increase the level or effect of prochlorperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• progesterone intravaginal gel

  Monitor Closely (1)ritonavir will increase the level or effect of progesterone intravaginal gel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• progesterone micronized

  Monitor Closely (1)ritonavir will increase the level or effect of progesterone micronized by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• progesterone, natural

  Monitor Closely (1)ritonavir will increase the level or effect of progesterone, natural by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• promazine

  Minor (1)ritonavir will increase the level or effect of promazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• promethazine

  Minor (1)ritonavir will increase the level or effect of promethazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• propafenone

  Serious - Use Alternative (2)ritonavir will increase the level or effect of propafenone by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Concurrent use of propafenone and ritonavir is contraindicated.
  
  ritonavir increases levels of propafenone by decreasing metabolism. Contraindicated.Minor (1)ritonavir will increase the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• propranolol

  Monitor Closely (1)ritonavir will increase the level or effect of propranolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.

• quazepam

  Serious - Use Alternative (1)ritonavir will increase the level or effect of quazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• quercetin

  Monitor Closely (1)quercetin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• quetiapine

  Monitor Closely (2)ritonavir will increase the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  quetiapine, ritonavir. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Avoid use with drugs that prolong QT and in patients with risk factors for prolonged QT interval. Postmarketing cases show QT prolongation with overdose in patients with concomitant illness or with drugs known to cause electrolyte imbalance or prolong QT.

• quinidine

  Monitor Closely (1)ritonavir will increase the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir increases levels of quinidine by decreasing metabolism. Contraindicated.
  
  quinidine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• quinine

  Serious - Use Alternative (1)ritonavir will increase the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Prescribing information for quinine recommends avoiding combination

• quinupristin/dalfopristin

  Monitor Closely (1)quinupristin/dalfopristin will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• rabeprazole

  Minor (1)ritonavir will increase the level or effect of rabeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ramelteon

  Minor (1)ritonavir will increase the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ranolazine

  Monitor Closely (1)ranolazine will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• red yeast rice

  Serious - Use Alternative (1)ritonavir will increase the level or effect of red yeast rice by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. May increase creatine kinase levels and increase risk of myopathy or rhabdomyolysis; red yeast rice contains monocolin K (reportedly identical to lovastatin)

• regorafenib

  Contraindicated (1)ritonavir, regorafenib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Strong CYP3A4 inhibitors increase regorafenib levels and decrease exposure of the active metabolites M-2 and M-5.

• repaglinide

  Monitor Closely (1)ritonavir will increase the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• revefenacin

  Serious - Use Alternative (1)ritonavir increases levels of revefenacin by Other (see comment). Avoid or Use Alternate Drug. Comment: OATP1B1 and OATP1B3 transport inhibitors may increase systemic exposure of revefenacin's active metabolite. Coadministration not recommended.

• ribociclib

  Monitor Closely (1)ribociclib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)ritonavir will increase the level or effect of ribociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If a strong CYP3A inhibitor must be coadministered with ribociclib, reduce the ribociclib starting dose to 400 mg/day.

• rifabutin

  Monitor Closely (1)ritonavir increases levels of rifabutin by decreasing metabolism. Use Caution/Monitor.Serious - Use Alternative (2)ritonavir will increase the level or effect of rifabutin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  rifabutin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rifampin

  Monitor Closely (1)rifampin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)rifampin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rifapentine

  Monitor Closely (1)rifapentine will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)rifapentine decreases levels of ritonavir by increasing metabolism. Contraindicated.

• rifaximin

  Monitor Closely (1)ritonavir increases levels of rifaximin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• rilpivirine

  Monitor Closely (2)ritonavir increases levels of rilpivirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No dose adjustment is required during concurrent use.
  
  rilpivirine increases toxicity of ritonavir by QTc interval. Use Caution/Monitor. Rilpivirine should be used with caution when co-administered with a drug with a known risk of Torsade de Pointes.

• rimegepant

  Serious - Use Alternative (2)ritonavir will increase the level or effect of rimegepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of rimegepant by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

• riociguat

  Serious - Use Alternative (3)ritonavir will increase the level or effect of riociguat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ritonavir will increase the level or effect of riociguat by decreasing metabolism. Avoid or Use Alternate Drug. Coadministration of riociguat (substrate of CYP isoenzymes 1A1, 2C8, 3A, 2J2) with strong CYP inhibitors may require a decreased initial dose of 0.5 mg PO TID; monitor for signs of hypotension and reduce dose if needed
  
  ritonavir will increase the level or effect of riociguat by Other (see comment). Avoid or Use Alternate Drug. Coadministration of riociguat (an ABCG2 [BCRP] substrate) with strong ABCG2 inhibitors may require a decreased initial dose of 0.5 mg PO TID; monitor for signs of hypotension and reduce dose if needed

• ripretinib

  Monitor Closely (1)ritonavir will increase the level or effect of ripretinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with a strong CYP3A inhibitor will increase systemic exposure to ripretinib and its active metabolite (DP-5439), which may increase risk of adverse reactions.

• risperidone

  Monitor Closely (1)ritonavir will increase the level or effect of risperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of risperidone by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• rivaroxaban

  Serious - Use Alternative (1)ritonavir increases levels of rivaroxaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of rivaroxaban and combined Pgp and strong CYP3A4 inhibitors. Combination may lead to significant increases in rivaroxaban levels and increase bleeding risk.

• roflumilast

  Monitor Closely (1)ritonavir will decrease the level or effect of roflumilast by affecting hepatic enzyme CYP1A2 metabolism. Modify Therapy/Monitor Closely. Concomitant therapy may reduce therapeutic effectiveness.Serious - Use Alternative (1)ritonavir will increase the level or effect of roflumilast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rolapitant

  Monitor Closely (1)rolapitant will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Rolapitant may increase plasma concentrations of CYP2D6 substrates for at least 28 days following rolapitant administration.

• romidepsin

  Monitor Closely (1)ritonavir will increase the level or effect of romidepsin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong 3A4 inhibitors should be avoided if possible.

• rosiglitazone

  Monitor Closely (1)ritonavir decreases effects of rosiglitazone by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• rosuvastatin

  Monitor Closely (1)ritonavir will increase the level or effect of rosuvastatin by decreasing metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases toxicity of rosuvastatin by Other (see comment). Avoid or Use Alternate Drug. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• rucaparib

  Monitor Closely (1)rucaparib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP3A4 substrates, if clinically indicated.

• rufinamide

  Monitor Closely (1)rufinamide will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ruxolitinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Reduce ruxolitinib starting dose to 10 mg BID with platelet count 100 X 10^9/L or more and concurrent use of strong CYP3A4 inhibitors; avoid with platelet counts <100 X 10^9/L

• ruxolitinib topical

  Serious - Use Alternative (1)ritonavir will increase the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Reduce ruxolitinib starting dose to 10 mg BID with platelet count 100 X 10^9/L or more and concurrent use of strong CYP3A4 inhibitors; avoid with platelet counts <100 X 10^9/L

• sacubitril/valsartan

  Monitor Closely (2)ritonavir will increase the level or effect of sacubitril/valsartan by Other (see comment). Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic uptake transporter OATP1B1; coadministration with OATP1B1 inhibitors may increase valsartan systemic exposure
  
  ritonavir will increase the level or effect of sacubitril/valsartan by Mechanism: decreasing hepatic clearance. Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic efflux transporter MRP2; coadministration of inhibitors of the efflux transporter may increase the systemic exposure to valsartan

• salmeterol

  Contraindicated (1)ritonavir increases levels of salmeterol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Potential for increased toxicity.

• saquinavir

  Monitor Closely (3)ritonavir will increase the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Saquinavir is intended to be administered with ritonavir (boosted therapy). The combination has shown to cause dose-dependent QT and PR interval prolongation. Caution in treatment naïve patients. Reduce starting dose and perform an on-treatment ECG after approximately 10 days.
  
  ritonavir will increase the level or effect of saquinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir and saquinavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.Serious - Use Alternative (1)saquinavir will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• sarecycline

  Monitor Closely (1)sarecycline will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor for toxicities of P-gp substrates that may require dosage reduction when coadministered with P-gp inhibitors.

• saxagliptin

  Monitor Closely (1)ritonavir will increase the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Limit saxagliptin dose to 2.5 mg/day when coadministered with strong CYP3A4 inhibitors

• secobarbital

  Monitor Closely (1)secobarbital will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• selexipag

  Minor (1)ritonavir will increase the level or effect of selexipag by decreasing metabolism. Minor/Significance Unknown. Coadministration of selexipag with ritonavir may result in an increase in exposure to selexipag. Despite this pharmacokinetic change, this interaction is likely of little clinical significance

• selpercatinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of selpercatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• selumetinib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of selumetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors cannot be avoided, reduce selumetinib dosage (refer to selumetinib monograph for further information). After discontinuation of the strong or moderate CYP3A4 inhibitor for 3 elimination half-lives, resume selumetinib dose that was taken before initiating the inhibitor.

• sertraline

  Monitor Closely (1)ritonavir increases levels of sertraline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased risk of serotonin syndrome.

• sildenafil

  Serious - Use Alternative (1)ritonavir will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If used concomitantly, monitor for toxicities. Patients receiving indinavir with ritonavir should receive not more than 25 mg of sildenafil for treatment of erectile dysfunction in a 48-hour period, and patients receiving other protease inhibitors should use a lower initial sildenafil dose of 25 mg. Patient taking sildenafil for PAH with ritonavir is not recommended.

• silodosin

  Monitor Closely (1)ritonavir will increase the level or effect of silodosin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• simvastatin

  Contraindicated (3)ritonavir will increase the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  simvastatin will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Contraindicated.
  
  ritonavir increases toxicity of simvastatin by Other (see comment). Contraindicated. Comment: OATP1B1 inhibitors may increase risk of myopathy.

• siponimod

  Serious - Use Alternative (1)ritonavir will increase the level or effect of siponimod by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of siponimod with a moderate or strong CYP3A4 inhibitor PLUS a moderate or strong CYP2C9 inhibitor is not recommended.

• sirolimus

  Monitor Closely (1)ritonavir will increase the level or effect of sirolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• sitagliptin

  Monitor Closely (1)ritonavir decreases effects of sitagliptin by Other (see comment). Use Caution/Monitor. Comment: Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• solifenacin

  Monitor Closely (1)ritonavir will increase the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sonidegib

  Serious - Use Alternative (1)ritonavir will increase the level or effect of sonidegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sonidegib with strong CYP3A4 inhibitors.

• sorafenib

  Monitor Closely (1)ritonavir will increase the level or effect of sorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sotorasib

  Serious - Use Alternative (1)sotorasib will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If use is unavoidable, refer to the prescribing information of the P-gp substrate for dosage modifications.

• St John's Wort

  Contraindicated (1)St John's Wort will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Monitor Closely (1)St John's Wort will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)St John's Wort decreases levels of ritonavir by increasing metabolism. Contraindicated.

• stavudine

  Monitor Closely (1)ritonavir and stavudine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• stiripentol

  Monitor Closely (2)stiripentol, ritonavir. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.
  
  stiripentol will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Consider reducing the dose of P-glycoprotein (P-gp) substrates, if adverse reactions are experienced when administered concomitantly with stiripentol.Serious - Use Alternative (1)ritonavir will increase the level or effect of stiripentol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• streptomycin

  Monitor Closely (1)ritonavir will increase the level or effect of streptomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• sufentanil

  Minor (1)ritonavir will increase the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• sufentanil SL

  Monitor Closely (1)ritonavir will increase the level or effect of sufentanil SL by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of sufentanil SL with any CYP3A4 inhibitor may increase sufentanil plasma concentration, and, thereby increase or prolonged adverse effects, including potentially fatal respiratory depression.

• sunitinib

  Monitor Closely (1)ritonavir will increase the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• suvorexant

  Serious - Use Alternative (1)ritonavir increases levels of suvorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Suvorexant not recommended with use of strong CYP3A4 inhibitors.

• tacrolimus

  Monitor Closely (2)ritonavir will increase the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of tacrolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• tacrolimus ointment

  Monitor Closely (1)ritonavir will increase the level or effect of tacrolimus ointment by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tadalafil

  Serious - Use Alternative (1)ritonavir will increase the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Stop tadalafil >24 hours prior to protease inhibitor (PI) initiation, restart 7 days after PI initiation at 20 mg once daily, and increase to 40 mg once daily based on tolerability.

• talazoparib

  Monitor Closely (1)ritonavir will increase the level or effect of talazoparib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Talazoparib is a P-glycoprotein (P-gp) substrate; coadministration with P-gp inhibitors may increase talazoparib systemic exposure.

• tamoxifen

  Monitor Closely (1)ritonavir, tamoxifen. affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. CYP2D6 inhibition decreases metabolism of tamoxifen to hydroxytamoxifen, and N-desmethyl tamoxifen to endoxifen (active metabolites with 100-fold greater affinity for estrogen receptor); decreased endoxifen levels may result in poor clinical outcome.Serious - Use Alternative (1)ritonavir, tamoxifen. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. CYP3A4 inhibition decreases metabolism of tamoxifen to N-desmethyl tamoxifen (active metabolite with similar biologic activity).

• tamsulosin

  Monitor Closely (1)ritonavir increases levels of tamsulosin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases levels of tamsulosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• tasimelteon

  Monitor Closely (1)ritonavir will increase the level or effect of tasimelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tazemetostat

  Monitor Closely (2)ritonavir will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  tazemetostat will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tecovirimat

  Monitor Closely (1)tecovirimat will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.

• temsirolimus

  Monitor Closely (1)ritonavir will increase the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• teniposide

  Monitor Closely (2)ritonavir will increase the level or effect of teniposide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of teniposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tenofovir DF

  Monitor Closely (2)ritonavir increases levels of tenofovir DF by decreasing elimination. Use Caution/Monitor.
  
  ritonavir and tenofovir DF both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• tepotinib

  Serious - Use Alternative (2)ritonavir will increase the level or effect of tepotinib by Other (see comment). Avoid or Use Alternate Drug. Interaction not studied clinically. Metabolism and data suggest drugs that are strong CYP3A4 and P-gp inhibitors may increase tepotinib (a P-gp and CYP3A4 substrate) effects and risk of toxicities.
  
  tepotinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If concomitant use unavoidable, reduce the P-gp substrate dosage if recommended in its approved product labeling.

• terbinafine

  Monitor Closely (2)ritonavir will increase the level or effect of terbinafine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  terbinafine will increase the level or effect of ritonavir by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Assess need to reduce dose of CYP2D6-metabolized drug.

• tetrabenazine

  Monitor Closely (1)ritonavir increases effects of tetrabenazine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Decrease tetrabenazine dose by 50% when coadministered with strong CYP2D6 inhibitors.

• tezacaftor

  Monitor Closely (1)ritonavir will increase the level or effect of tezacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust tezacaftor dosage regimen if coadministered with a strong CYP3A inhibitor.

• theophylline

  Monitor Closely (1)ritonavir will increase the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• thioridazine

  Serious - Use Alternative (1)ritonavir will increase the level or effect of thioridazine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug.

• tiagabine

  Monitor Closely (1)ritonavir will increase the level or effect of tiagabine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ticagrelor

  Monitor Closely (1)ritonavir increases levels of ticagrelor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Ticagrelor is metabolized by CYP3A4/5. Avoid use with strong CYP3A inhibitors.

• timolol

  Monitor Closely (1)ritonavir increases levels of timolol by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Potential for increased toxicity. Increased risk of hypotension, bradycardia, AV block, and prolonged PR interval. Consider lowering beta blocker dose.

• tinidazole

  Contraindicated (1)tinidazole increases toxicity of ritonavir by aldehyde dehydrogenase inhibition. Contraindicated. Interaction only associated with oral solution, which contains 42% alcohol.Monitor Closely (1)ritonavir will increase the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tipranavir

  Monitor Closely (2)ritonavir will increase the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of tipranavir with ritonavir is essential to achieve effective tipranavir plasma concentrations (boosted therapy).
  
  ritonavir and tipranavir both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• tisotumab vedotin

  Monitor Closely (1)ritonavir increases levels of tisotumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tisotumab vedotin?s active metabolite (MMAE) is a CYP3A4 substrate. Coadministration with strong CYP3A4 inhibitors may increase unconjugated MMAE systemic exposure and increase risk of adverse effects.

• tobramycin

  Monitor Closely (1)ritonavir will increase the level or effect of tobramycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• tofacitinib

  Serious - Use Alternative (1)ritonavir increases levels of tofacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Reduce tofacitinib dose to 5 mg qDay when coadministered with potent CYP3A4 inhibitors.

• tolazamide

  Monitor Closely (1)ritonavir, tolazamide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of tolazamide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• tolbutamide

  Monitor Closely (1)ritonavir, tolbutamide. Other (see comment). Use Caution/Monitor. Comment: Ritonavir may increase or decrease levels of tolbutamide. Reports of hyperglycemia due to insulin resistance with protease inhibitors. .

• tolterodine

  Monitor Closely (1)ritonavir will increase the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of tolterodine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• tolvaptan

  Monitor Closely (2)ritonavir will increase the level or effect of tolvaptan by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  tolvaptan will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir will increase the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

• topiramate

  Monitor Closely (1)topiramate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• topotecan

  Serious - Use Alternative (1)ritonavir will increase the level or effect of topotecan by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Product labeling for PO topotecan recommends avoiding concomitant use of P-gp inhibitors; the interaction with IV topotecan may be less severe but is still likely of clinical significance

• toremifene

  Monitor Closely (1)ritonavir increases levels of toremifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Metabolism of toremifene may be inhibited by drugs known to inhibit CYP3A4 hepatic enzymes.

• trabectedin

  Serious - Use Alternative (1)ritonavir will increase the level or effect of trabectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If strong CYP3A inhibitor must be used, short-term (eg, less than 14 days), administer strong CYP3A inhibitor 1 week after trabectedin infusion, and discontinue the day prior to next trabectedin infusion

• tramadol

  Monitor Closely (1)ritonavir will increase the level or effect of tramadol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. May require decreased tramadol dose or adjustment of dosing interval; increased risk for serious adverse events including seizures and serotonin syndrome

• trazodone

  Monitor Closely (2)trazodone will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  ritonavir will increase the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• triamcinolone acetonide injectable suspension

  Monitor Closely (1)ritonavir will increase the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• triazolam

  Monitor Closely (1)ritonavir will increase the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)ritonavir increases levels of triazolam by decreasing metabolism. Contraindicated.

• trifluoperazine

  Minor (1)ritonavir will increase the level or effect of trifluoperazine by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• trimipramine

  Monitor Closely (1)ritonavir will increase the level or effect of trimipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tropisetron

  Minor (1)ritonavir will increase the level or effect of tropisetron by affecting hepatic enzyme CYP2D6 metabolism. Minor/Significance Unknown.

• tucatinib

  Monitor Closely (1)tucatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Consider reducing the dosage of P-gp substrates, where minimal concentration changes may lead to serious or life-threatening toxicities.Serious - Use Alternative (2)ritonavir will increase the level or effect of tucatinib by Other (see comment). Avoid or Use Alternate Drug. Coadministration of tucatinib (a CYP2C8 substrate) with a strong or moderate CYP2C8 inhibitors increases tucatinib plasma concentrations and risk of toxicities.
  
  tucatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.

• ubrogepant

  Monitor Closely (1)ritonavir will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Dose adjustment is recommended with concomitant use of ubrogepant and moderate and weak CYP3A4 inducers. (see Dosage Modifications)

• ulipristal

  Monitor Closely (1)ritonavir will increase the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• umeclidinium bromide/vilanterol inhaled

  Monitor Closely (1)ritonavir will increase the level or effect of umeclidinium bromide/vilanterol inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Vilanterol is a CYP3A4 substrate; coadministration with potent CYP3A4 inhibitors may increase systemic exposure

• upadacitinib

  Monitor Closely (1)ritonavir will increase the level or effect of upadacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Caution if upadacitinib is coadministered with strong CYP3A4 inhibitors.

• valbenazine

  Monitor Closely (2)ritonavir will increase the level or effect of valbenazine by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Consider reducing valbenazine dose based on tolerability if coadministered with a strong CYP2D6 inhibitor.
  
  ritonavir will increase the level or effect of valbenazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce valbenazine dose to 40 mg once daily when coadministered with a strong CYP3A4 inhibitor.

• valsartan

  Monitor Closely (2)ritonavir will increase the level or effect of valsartan by Other (see comment). Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic uptake transporter OATP1B1; coadministration with OATP1B1 inhibitors may increase valsartan systemic exposure
  
  ritonavir will increase the level or effect of valsartan by Mechanism: decreasing hepatic clearance. Use Caution/Monitor. The results from an in vitro study with human liver tissue indicate that valsartan is a substrate of the hepatic efflux transporter MRP2; coadministration of inhibitors of the efflux transporter may increase the systemic exposure to valsartan

• vardenafil

  Monitor Closely (1)ritonavir will increase the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• vemurafenib

  Monitor Closely (2)ritonavir increases levels of vemurafenib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.
  
  vemurafenib increases levels of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Serious - Use Alternative (2)vemurafenib and ritonavir both increase QTc interval. Avoid or Use Alternate Drug. Concomitant use of vemurafenib with drugs that prolong QT interval is not recommended.
  
  ritonavir increases levels of vemurafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• venetoclax

  Contraindicated (1)ritonavir will increase the level or effect of venetoclax by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Use of strong CYP3A4 inhibitors is contraindicated with venetoclax during the initial ramp-up dosing phase. If a strong CYP3A inhibitor must be used after the ramp-up phase, reduce the venetoclax dose by at least 75%.

• venlafaxine

  Monitor Closely (1)ritonavir increases levels of venlafaxine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .

• verapamil

  Monitor Closely (2)ritonavir will increase the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  verapamil will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

• vilanterol/fluticasone furoate inhaled

  Monitor Closely (1)ritonavir will increase the level or effect of vilanterol/fluticasone furoate inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Fluticasone furoate and vilanterol are both CYP3A4 substrates; coadministration with potent CYP3A4 inhibitors may increase systemic exposure

• vilazodone

  Serious - Use Alternative (1)ritonavir increases levels of vilazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inhibitors may increase vilazodone plasma levels by 50% - Reduce daily dose to 20 mg.

• vinblastine

  Monitor Closely (1)ritonavir will increase the level or effect of vinblastine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of vinblastine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• vincristine

  Monitor Closely (1)ritonavir will increase the level or effect of vincristine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of vincristine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• vincristine liposomal

  Monitor Closely (1)ritonavir will increase the level or effect of vincristine liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.Minor (1)ritonavir will increase the level or effect of vincristine liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• vinorelbine

  Minor (1)ritonavir will increase the level or effect of vinorelbine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• voclosporin

  Contraindicated (1)ritonavir will increase the level or effect of voclosporin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Monitor Closely (1)voclosporin, ritonavir. Either increases effects of the other by QTc interval. Use Caution/Monitor.

• vorapaxar

  Serious - Use Alternative (1)ritonavir increases levels of vorapaxar by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• voriconazole

  Contraindicated (2)voriconazole will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.
  
  ritonavir decreases levels of voriconazole by increasing metabolism. Contraindicated. Ritonavir 400 mg BID decreases voriconazole levels; lower ritonavir doses have unknown effect.Serious - Use Alternative (1)ritonavir will increase the level or effect of voriconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• vortioxetine

  Serious - Use Alternative (1)ritonavir increases levels of vortioxetine by affecting hepatic enzyme CYP2D6 metabolism. Avoid or Use Alternate Drug. Decrease vortioxetine dose by 50% when coadministered with strong CYP2D6 inhibitors.

• voxelotor

  Serious - Use Alternative (1)voxelotor will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.

• warfarin

  Monitor Closely (1)ritonavir will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

• zafirlukast

  Monitor Closely (1)zafirlukast will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• zaleplon

  Minor (1)ritonavir will increase the level or effect of zaleplon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zanubrutinib

  Monitor Closely (1)ritonavir will increase the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce zanubrutinib dose when coadministered with a strong CYP3A4 inhibitor. Interrupt dose as recommended for adverse reactions. After discontinuing the CYP3A4 inhibitor, resume previous dose of zanubrutinib. See zanubrutinib Dosage Modifications for precise recommendation.

• zidovudine

  Monitor Closely (1)ritonavir and zidovudine both increase risk of immune reconstitution syndrome. Use Caution/Monitor.

• zileuton

  Monitor Closely (1)ritonavir increases levels of zileuton by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Potential for increased toxicity. .

• ziprasidone

  Minor (1)ritonavir will increase the level or effect of ziprasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zolpidem

  Minor (1)ritonavir will increase the level or effect of zolpidem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zonisamide

  Minor (1)ritonavir will increase the level or effect of zonisamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.