isoniazid (Rx)

Latent Tuberculosis Infection

Treatment of latent TB infection greatly reduces the risk that TB infection will progress to acitve disease

>30 kg: 300 mg PO qDay x9 months  

3-month regimen

• Recommended for patients aged 12 years and older who are at high risk for developing TB disease including anyone who has had recent exposure to contagious TB, conversion from negative to positive on a test for TB infection, or a chest X-ray indicating prior TB disease
• Persons with HIV who are otherwise healthy and not taking antiretrovirals may also use this regimen
• 900 mg PO once weekly x3 months (administer with rifapentine 900 mg once weekly)
• Administered as DOT
• Not recommended for children <2 years, pregnant women or women planning to become pregnant, HIV-infected persons taking antiretrovirals, and patients whose TB infection is presumed to be the result of exposure to a person with TB disease that is resistant to 1 of the 2 drugs
• References: CDC MMWR 2011;60:1650-3 and NEJM 2011;365:2155-2166

Active Tuberculosis Disease

5 mg/kg PO/IM qDay, not to exceed 300 mg qDay  

15 mg/kg PO/IM up; not to exceed 900 mg 1-3 times/week

Used in multi-drug regimen containing rifampin (or ribabutin or rifapentin), pyrazinamide, and ethambutol

Duration of treatment dependent on regimen consisting of an initial phase of treatment and a continutation phase of treatment

Note: Daily treatment has best results for HIV positive individuals

See Also Combos

With rifampin (Rifamate)

With rifampin and pyrizinamide (Rifater)

Other Indications & Uses

Newly infected patients

Household members and close associates of people recently diagnosed wtih TB

+ve TB skin test with +ve non-progressive chest x-ray

+ve TB skin test with underlying disease or immunosuppression

+ve TB skin test, <35 years old; >35 years old weigh use against risk of hepatitis

Latent Tuberculosis Infection

Treatment of latent TB infection greatly reduces the risk that TB infection will progress to acitve disease

10-15 mg/kg PO qDay; not to exceed 300 mg/day  

3-month regimen

• Recommended for patients aged 12 years and older who are at high risk for developing TB disease including anyone who has had recent exposure to contagious TB, conversion from negative to positive on a test for TB infection, or a chest X-ray indicating prior TB disease
• Use for children aged 2-11 years and patients with underlying conditions associated with TB should be considered on a case-by-case basis; preferred regimen for this age group is daily isoniazid for 9 months
• Not recommended for children <2 years
• >12 years: isoniazid 900 mg PO plus rifapentine 900 mg PO once weekly for 3 months
• References: CDC MMWR 2011;60:1650-3 and NEJM 2011;365:2155-2166

Active Tuberculosis Disease

10-15 mg/kg PO qDay; not to exceed 300 mg/day OR  

20-30 mg/kg (up to 900 mg) 2 times/week

Used in multi-drug regimen

Contraindicated (20)

• cobimetinib

  isoniazid 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

  isoniazid 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

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

• dihydroergotamine intranasal

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

• eliglustat

  isoniazid 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
  
  isoniazid 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.

• flibanserin

  isoniazid 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.

• infigratinib

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

• ivabradine

  isoniazid 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.

• ketoconazole

  isoniazid decreases levels of ketoconazole by unspecified interaction mechanism. Contraindicated.

• levoketoconazole

  isoniazid decreases levels of levoketoconazole by unspecified interaction mechanism. Contraindicated.

• lomitapide

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

• lonafarnib

  isoniazid 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

  isoniazid 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

• lurasidone

  isoniazid 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

  isoniazid will increase the level or effect of mavacamten by affecting hepatic enzyme CYP2C19 metabolism. Contraindicated. Strong or moderate CYP2C19 inhibitors may increase mavacamten systemic exposure, resulting in heart failure due to systolic dysfunction.

• naloxegol

  isoniazid 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

• pacritinib

  isoniazid will increase the level or effect of pacritinib by affecting hepatic enzyme CYP2E1 metabolism. Contraindicated.

• regorafenib

  isoniazid, 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.

• venetoclax

  isoniazid 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

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

Serious - Use Alternative (100)

• acalabrutinib

  isoniazid 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

  isoniazid 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.

• alfentanil

  isoniazid will increase the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Monitor for excessive CNS and respiratory depression

• alfuzosin

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

• avanafil

  isoniazid 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

  isoniazid 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 moderate CYP3A4 inhibitors. If unable to avoid, reduce avapritinib starting dose. See drug monograph Dosage Modifications.

• axitinib

  isoniazid 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

  isoniazid 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

• bosutinib

  isoniazid 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.

• brigatinib

  isoniazid 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.

• cabazitaxel

  isoniazid will increase the level or effect of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of cabazitaxel with strong CYP3A4 inhibitors should be avoided.

• cabozantinib

  isoniazid 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.

• ceritinib

  isoniazid 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.

• cilostazol

  isoniazid increases toxicity of cilostazol by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. Decrease cilostazol dose by 50%; serum levels of 3,4-dehydrocilostazol (active metabolite) increased by strong CYP2C19 inhibitors.

• clopidogrel

  isoniazid decreases effects of clopidogrel by decreasing metabolism. Avoid or Use Alternate Drug. Cytochrome P450 2C19 inhibitors decrease the conversion of clopidogrel to its active form.

• copanlisib

  isoniazid 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

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

• desvenlafaxine

  isoniazid and desvenlafaxine both increase serotonin levels. Avoid or Use Alternate Drug.

• dronedarone

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

• elacestrant

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

• encorafenib

  isoniazid 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

  isoniazid will increase the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of moderate CYP3A4 inhibitors with entrectinib, a CYP3A4 substrate. If coadministration unavoidable, reduce dose to 200 mg/day for patients aged 12 y or older with BSA >1.50m2. Resume previous entrectinib dose after discontinuing moderate CYP3A inhibitor for 3-5 elimination half-lives.

• eplerenone

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

• erdafitinib

  isoniazid 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.

• ergotamine

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

• erythromycin base

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

• erythromycin ethylsuccinate

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

• erythromycin lactobionate

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

• erythromycin stearate

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

• esomeprazole

  isoniazid will increase the level or effect of esomeprazole by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

• etravirine

  isoniazid will increase the level or effect of etravirine by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

• everolimus

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

• fedratinib

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

• fentanyl

  isoniazid 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

  isoniazid 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

  isoniazid 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

  isoniazid 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

  isoniazid 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.

• fluticasone intranasal

  isoniazid 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.

• gilteritinib

  isoniazid 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.

• glasdegib

  isoniazid 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.

• ibrutinib

  isoniazid 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

  isoniazid 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

• irinotecan

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

• irinotecan liposomal

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

• isocarboxazid

  isocarboxazid and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug.

• lefamulin

  isoniazid 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

  isoniazid 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.

• linezolid

  linezolid and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug. Linezolid may increase serotonin as a result of MAO-A inhibition. If linezolid must be administered, discontinue serotonergic drug immediately and monitor for CNS toxicity. Serotonergic therapy may be resumed 24 hours after last linezolid dose or after 2 weeks of monitoring, whichever comes first.

• lorcaserin

  isoniazid and lorcaserin both increase serotonin levels. Avoid or Use Alternate Drug.

• lorlatinib

  isoniazid 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.

• lurbinectedin

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

• macitentan

  isoniazid 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

• methylene blue

  methylene blue and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug. Methylene blue and isoniazid may increase serotonin as a result of MAO-A inhibition. If methylene blue must be administered, discontinue isoniazid immediately and monitor for CNS toxicity. Isoniazid may be resumed 24 hours after last methylene blue dose or after 2 weeks of monitoring, whichever comes first.

• midazolam intranasal

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

• midostaurin

  isoniazid 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.

• mirtazapine

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

• mobocertinib

  isoniazid will increase the level or effect of mobocertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If use of moderate CYP3A4 inhibitor unavoidable, reduce mobocertinib dose by ~50% (eg, 160 to 80 mg); closely monitor QTc interval.

• neratinib

  isoniazid 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

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

• nisoldipine

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

• olaparib

  isoniazid 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.

• omaveloxolone

  isoniazid will increase the level or effect of omaveloxolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unavoidable, reduce omaveloxolone dose to 100 mg/day. Closely monitor for adverse effects. If adverse effects emerge, further reduce to 50 mg/day.

• omeprazole

  isoniazid will increase the level or effect of omeprazole by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

• osimertinib

  isoniazid 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

  isoniazid 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

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

• palbociclib

  isoniazid 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.

• pemigatinib

  isoniazid 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

  isoniazid 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.
  
  isoniazid and pexidartinib both increase inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug. Pexidartinib can cause hepatotoxicity. Avoid coadministration of pexidartinib with other products know to cause hepatoxicity.

• phenelzine

  phenelzine and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug.

• pimavanserin

  isoniazid 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

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

• pomalidomide

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

• ponatinib

  isoniazid 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

  isoniazid will increase the level or effect of pralsetinib by affecting hepatic enzyme CYP2E1 metabolism. Avoid or Use Alternate Drug.

• pretomanid

  isoniazid, pretomanid. Either increases toxicity of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Pretomanid regimen associated with hepatotoxicity. Avoid alcohol and hepatotoxic agents, including herbal supplements and drugs other than bedaquiline and linezolid.

• ranolazine

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

• red yeast rice

  isoniazid 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)

• rifampin

  rifampin increases toxicity of isoniazid by increasing metabolism. Avoid or Use Alternate Drug. Rifampin enhances the metabolism of isoniazid to hepatotoxic metabolites.

• rimegepant

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

• riociguat

  isoniazid 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

• ruxolitinib

  isoniazid 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

  isoniazid 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

• selumetinib

  isoniazid 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.

• silodosin

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

• simvastatin

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

• siponimod

  isoniazid 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

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

• sonidegib

  isoniazid 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.

• suvorexant

  isoniazid 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.

• tamsulosin

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

• tazemetostat

  isoniazid will increase the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of tazemetostat with moderate CYP3A4 inhibitors. If coadministration is unavoidable, reduce tazemetostat current dose (see drug monograph Dosage Modifications).

• tofacitinib

  isoniazid 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

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

• trabectedin

  isoniazid 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

• tranylcypromine

  tranylcypromine and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug.

• vemurafenib

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

• vilazodone

  isoniazid, vilazodone. Either increases toxicity of the other by serotonin levels. Avoid or Use Alternate Drug. Concomitant therapy should be discontinued immediately if signs or symptoms of serotonin syndrome emerge and supportive symptomatic treatment should be initiated. .
  
  isoniazid 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

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

Monitor Closely (262)

• 5-HTP

  5-HTP and isoniazid both increase serotonin levels. Use Caution/Monitor.

• abemaciclib

  isoniazid 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.

• abrocitinib

  isoniazid will increase the level or effect of abrocitinib by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Start abrocitinib 50 mg qDay when coadministered with CYP2C19 inhibitors. If adequate response not achieved after 12 weeks, may increase to 100 mg qDay. Discontinue if inadequate response after dosage increase.

• acetaminophen

  isoniazid will increase the level or effect of acetaminophen by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• acetaminophen IV

  isoniazid will increase the level or effect of acetaminophen IV by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• acetaminophen rectal

  isoniazid will increase the level or effect of acetaminophen rectal by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• almotriptan

  isoniazid will increase the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  almotriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• alosetron

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

• alprazolam

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

• aluminum hydroxide

  aluminum hydroxide decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• amifampridine

  isoniazid increases toxicity of amifampridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Amifampridine can cause seizures. Coadministration with drugs that lower seizure threshold may increase this risk.

• amiodarone

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

• amitriptyline

  isoniazid will increase the level or effect of amitriptyline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  amitriptyline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• amoxapine

  amoxapine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• apalutamide

  isoniazid 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

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

• aripiprazole

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

• armodafinil

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

• artemether/lumefantrine

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

• atazanavir

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

• atogepant

  isoniazid 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.

• atorvastatin

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

• belzutifan

  isoniazid will increase the level or effect of belzutifan by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Belzutifan is a CYP2C19 substrate. Coadministration with CYP2C19 inhibitors may increase incidence or severity of adverse effects. Monitor for anemia and hypoxia and reduce belzutifan dose as recommended.

• benzhydrocodone/acetaminophen

  isoniazid 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.

• bexarotene

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

• bortezomib

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

• bosentan

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

• brentuximab vedotin

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

• brexpiprazole

  isoniazid 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.
  
  isoniazid will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer a quarter of brexpiprazole dose if coadministered with a moderate CYP2D6 inhibitor PLUS a strong/moderate CYP3A4 inhibitor.

• budesonide

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

• buprenorphine subdermal implant

  isoniazid 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, long-acting injection

  isoniazid 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.

• buspirone

  isoniazid will increase the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  buspirone and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• calcifediol

  isoniazid, 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.

• calcium carbonate

  calcium carbonate decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• cannabidiol

  isoniazid 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.
  
  isoniazid will increase the level or effect of cannabidiol by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider reducing the cannabidiol dose when coadministered with a strong CYP2C19 inhibitor.

• carbamazepine

  isoniazid 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

  isoniazid 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.

• cevimeline

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

• cilostazol

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

• cimetidine

  isoniazid will increase the level or effect of cimetidine by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• cinacalcet

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

• citalopram

  isoniazid will increase the level or effect of citalopram by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Citalopram 20 mg/day is the maximum recommended dose for patients taking CYP2C19 inhibitors because of the risk of QT prolongation.

• clarithromycin

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

• clobazam

  isoniazid will increase the level or effect of clobazam by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Dosage adjustment may be required; CYP2C19 inhibitors may result in increased exposure to N-desmethylclobazam (active metabolite).

• clomipramine

  clomipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• clopidogrel

  isoniazid 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

• clorazepate

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

• clozapine

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

• cobicistat

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

• cocaine topical

  cocaine topical and isoniazid both increase serotonin levels. Use Caution/Monitor.

• codeine

  isoniazid decreases effects of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.

• cortisone

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

• crizotinib

  isoniazid increases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use of strong CYP3A inhibitors should be avoided. .

• cycloserine

  isoniazid increases toxicity of cycloserine by decreasing metabolism. Use Caution/Monitor. Enhanced CNS toxicity; risk of seizure.

• dapsone

  isoniazid will increase the level or effect of dapsone by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.
  
  isoniazid will increase the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• daridorexant

  isoniazid will increase the level or effect of daridorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Daridorexant dose should not exceed 25 mg per night when coadministered with moderate CYP3A4 inhibitors.

• darifenacin

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

• darunavir

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

• dasatinib

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

• deflazacort

  isoniazid 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

  desipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• dexamethasone

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

• dexfenfluramine

  dexfenfluramine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• dextroamphetamine

  dextroamphetamine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• dextromethorphan

  dextromethorphan and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• diazepam

  isoniazid will increase the level or effect of diazepam by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  isoniazid will increase the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• diazepam intranasal

  isoniazid will increase the level or effect of diazepam intranasal by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Strong or moderate CYP2C19 inhibitors may decrease rate of diazepam elimination, thereby increasing adverse reactions to diazepam.
  
  isoniazid 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.

• dichlorphenamide

  dichlorphenamide, isoniazid. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Both drugs can cause metabolic acidosis.

• dienogest/estradiol valerate

  isoniazid will increase the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor for potential adverse effects such as nausea, irregular uterine bleeding, breast tenderness and headache.

• dihydroergotamine

  dihydroergotamine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• dihydroergotamine intranasal

  dihydroergotamine intranasal and isoniazid both increase serotonin levels. Use Caution/Monitor.

• disopyramide

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

• disulfiram

  disulfiram will increase the level or effect of isoniazid by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.
  
  isoniazid increases toxicity of disulfiram by decreasing metabolism. Use Caution/Monitor. Enhanced CNS toxicity.

• docetaxel

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

• doravirine

  isoniazid 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

  doxepin and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• doxorubicin

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

• doxorubicin liposomal

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

• dronabinol

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

• duloxetine

  duloxetine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• dutasteride

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

• efavirenz

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

• elagolix

  isoniazid will increase the level or effect of elagolix by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of elagolix 200 mg BID with strong CYP3A inhibitors for >1 month is not recommended. Limit elagolix dose to 150 mg qDay and CYP3A inhibitor duration of use to 6 months if coadministered.

• eletriptan

  isoniazid will increase the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  eletriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• eluxadoline

  isoniazid increases levels of eluxadoline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. As a precautionary measure due to incomplete information on the metabolism of eluxadoline, use caution when coadministered with strong CYP2C19 inhibitors.

• elvitegravir

  isoniazid increases levels of elvitegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Elvitegravir is a CYP3A4 substrate; if coadministered with strong CYP3A4 inhibitors may increase levels.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  isoniazid will increase the level or effect of elvitegravir/cobicistat/emtricitabine/tenofovir DF by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• enfortumab vedotin

  isoniazid 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.

• ergotamine

  ergotamine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• erlotinib

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

• escitalopram

  isoniazid will increase the level or effect of escitalopram by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  escitalopram and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• estradiol vaginal

  isoniazid 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.

• ethanol

  isoniazid will increase the level or effect of ethanol by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor. Generally avoid; increased risk of hepatotoxicity

• ethionamide

  ethionamide increases levels of isoniazid by unspecified interaction mechanism. Use Caution/Monitor.

• etonogestrel

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

• etoposide

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

• etravirine

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

• felodipine

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

• fenfluramine

  fenfluramine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• fesoterodine

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

• finasteride

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

• finerenone

  isoniazid will increase the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor serum potassium during initiation and dosage adjustment of either finererone or moderate CYP3A4 inhibitors. Adjust finererone dosage as needed.

• flibanserin

  isoniazid will increase the level or effect of flibanserin by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Coadministration of flibanserin with strong CYP2C19 inhibitors may increase flibanserin exposure and increase the risk of hypotension, syncope, and CNS depression.

• fludrocortisone

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

• fluoxetine

  fluoxetine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• fluticasone furoate

  isoniazid 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

  isoniazid 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

• fluvoxamine

  fluvoxamine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• fosamprenavir

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

• fosaprepitant

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

• frovatriptan

  frovatriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• galantamine

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

• gefitinib

  isoniazid 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.

• gepirone

  isoniazid will increase the level or effect of gepirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce gepirone dose by 50% when used concomitantly with a moderate CYP3A4 inhibitor.
  
  gepirone and isoniazid both increase serotonin levels. Use Caution/Monitor. Monitor for symptoms of serotonin syndrome when gepirone is used gepirone with other drugs that may affect the serotonergic neurotransmitter systems. If serotonin syndrome occurs, consider discontinue gepirone and/or concomitant serotonergic drug.

• glecaprevir/pibrentasvir

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

• green tea

  green tea, isoniazid. Other (see comment). Use Caution/Monitor. Comment: Avoid combination or excessive consumption of green tea. Combination may increase risk of cardiac arrhythmias or severe hypertension can occur due to caffeine component of green tea.

• guanfacine

  isoniazid 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

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

• hydrocodone

  isoniazid 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

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

• hydroxyprogesterone caproate (DSC)

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

• iloperidone

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

• imatinib

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

• imipramine

  isoniazid will increase the level or effect of imipramine by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  imipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• indinavir

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

• insulin degludec

  isoniazid decreases effects of insulin degludec by pharmacodynamic antagonism. Use Caution/Monitor. Isoniazid may increase blood glucose (rare).

• insulin degludec/insulin aspart

  isoniazid decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Use Caution/Monitor. Isoniazid may increase blood glucose (rare).

• insulin inhaled

  isoniazid decreases effects of insulin inhaled by pharmacodynamic antagonism. Use Caution/Monitor. Isoniazid may increase blood glucose (rare).

• isavuconazonium sulfate

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

• isradipine

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

• istradefylline

  isoniazid 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

  isoniazid decreases levels of itraconazole by unspecified interaction mechanism. Use Caution/Monitor.

• ivacaftor

  isoniazid 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.

• ixabepilone

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

• L-tryptophan

  isoniazid and L-tryptophan both increase serotonin levels. Use Caution/Monitor.

• lacosamide

  isoniazid increases levels of lacosamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider decreasing lacosamide dose when coadministered with strong CYP3A4 inhibitors.

• lansoprazole

  isoniazid will increase the level or effect of lansoprazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• lapatinib

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

• levamlodipine

  isoniazid will increase the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with moderate and strong CYP3A inhibitors results in increased systemic exposure to amlodipine and may require dose reduction. Monitor for symptoms of hypotension and edema when amlodipine is coadministered with CYP3A inhibitors to determine the need for dose adjustment.

• levodopa inhaled

  isoniazid decreases effects of levodopa inhaled by altering metabolism. Use Caution/Monitor. Isoniazid may inhibit dopa-decarboxylase in the brain; thereby, preventing conversion of levodopa to active dopamine.

• levomilnacipran

  levomilnacipran and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.
  
  isoniazid 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 oral/ethinylestradiol/ferrous bisglycinate

  isoniazid will increase the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with CYP3A4 inhibitors may increase the plasma hormone concentrations. Use of a nonhormonal contraceptive is recommended.

• lithium

  isoniazid and lithium both increase serotonin levels. Use Caution/Monitor.

• lofepramine

  lofepramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• lopinavir

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

• loratadine

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

• lsd

  isoniazid and lsd both increase serotonin levels. Use Caution/Monitor.

• lumacaftor/ivacaftor

  isoniazid 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

  isoniazid will increase the level or effect of lumateperone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce lumateperone dose to 21 mg/day if coadministered with moderate CYP3A4 inhibitors.

• lumefantrine

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

• maprotiline

  maprotiline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• maraviroc

  isoniazid 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

• mavacamten

  isoniazid will increase the level or effect of mavacamten by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Inititiation of moderate CYP3A4 inhibitors may require decreased mavacamten dose.

• medroxyprogesterone

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

• mefloquine

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

• meperidine

  isoniazid and meperidine both increase serotonin levels. Modify Therapy/Monitor Closely.

• metformin

  isoniazid decreases effects of metformin by unspecified interaction mechanism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.

• methadone

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

• methylprednisolone

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

• metronidazole

  metronidazole will increase the level or effect of isoniazid by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• midazolam

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

• milnacipran

  milnacipran and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• mipomersen

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

• mirtazapine

  isoniazid and mirtazapine both increase serotonin levels. Use Caution/Monitor.

• morphine

  isoniazid and morphine both increase serotonin levels. Use Caution/Monitor.

• naldemedine

  isoniazid 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.

• naratriptan

  naratriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• nefazodone

  nefazodone and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• nelfinavir

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

• netupitant/palonosetron

  isoniazid 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

• nicardipine

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

• nifedipine

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

• nimodipine

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

• nitrendipine

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

• norgestrel

  isoniazid will increase the level or effect of norgestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inhibitors may increase systemic concentration of norgestrel, which may increase risk for adverse effects

• nortriptyline

  nortriptyline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• oliceridine

  isoniazid 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.
  
  isoniazid 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.

• ondansetron

  isoniazid will increase the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP-450 inhibitors may decrease clearance of ondansetron. However, no dosage adjustment for ondansetron is recommended

• osilodrostat

  isoniazid 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

  isoniazid increases levels of ospemifene by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  isoniazid increases levels of ospemifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• paclitaxel

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

• paclitaxel protein bound

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

• palovarotene

  isoniazid will increase the level or effect of palovarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Avoid coadministration of palovarotene, a CYP3A substrate, with moderate CYP3A inhibitors. If unavoidable, reduce palovarotene dose by 50%.

• panobinostat

  isoniazid 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.

• paroxetine

  paroxetine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• pazopanib

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

• pentazocine

  isoniazid and pentazocine both increase serotonin levels. Use Caution/Monitor.

• pimozide

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

• polatuzumab vedotin

  isoniazid 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.

• prednisolone

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

• prednisone

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

• propafenone

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

• protriptyline

  protriptyline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• quetiapine

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

• quinidine

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

• quinine

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

• rasagiline

  rasagiline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• repaglinide

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

• rilpivirine

  isoniazid increases levels of rilpivirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ripretinib

  isoniazid 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.

• ritonavir

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

• rizatriptan

  rizatriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• romidepsin

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

• safinamide

  isoniazid, safinamide. Either increases toxicity of the other by serotonin levels. Modify Therapy/Monitor Closely. Monitor for hypertension and reaction to dietary tyramine in patients treated concomitantly with isoniazid and safinamide.

• SAMe

  isoniazid and SAMe both increase serotonin levels. Use Caution/Monitor.

• saquinavir

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

• saxagliptin

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

• selegiline

  selegiline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• selegiline transdermal

  selegiline transdermal and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• sertraline

  sertraline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• sevoflurane

  isoniazid will increase the level or effect of sevoflurane by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• sildenafil

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

• sodium bicarbonate

  sodium bicarbonate decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• sodium citrate/citric acid

  sodium citrate/citric acid decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• sodium picosulfate/magnesium oxide/anhydrous citric acid

  isoniazid decreases effects of sodium picosulfate/magnesium oxide/anhydrous citric acid by altering metabolism. Use Caution/Monitor. Coadministration with antibiotics decreases efficacy by altering colonic bacterial flora needed to convert sodium picosulfate to active drug.

• sodium sulfate/?magnesium sulfate/potassium chloride

  sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of isoniazid by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• sodium sulfate/potassium sulfate/magnesium sulfate

  sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of isoniazid by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• solifenacin

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

• St John's Wort

  isoniazid and St John's Wort both increase serotonin levels. Modify Therapy/Monitor Closely.

• sufentanil

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

• sufentanil SL

  isoniazid 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.

• sumatriptan

  sumatriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• sumatriptan intranasal

  sumatriptan intranasal and isoniazid both increase serotonin levels. Use Caution/Monitor.

• sunitinib

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

• tacrolimus

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

• tadalafil

  isoniazid will increase the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For ED limit tadalafil to max of 2.5 mg/day (for daily use) or 10 mg dose every 72 hr (for use as needed). Avoid concurrent use of tadalafil for pulmonary HTN in patients taking strong CYP3A4 inhibitors.

• tamoxifen

  isoniazid, tamoxifen. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. CYP3A4 inhibition decreases metabolism of tamoxifen to N-desmethyl tamoxifen (active metabolite with similar biologic activity).

• tamsulosin

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

• tasimelteon

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

• temsirolimus

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

• terbinafine

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

• tezacaftor

  isoniazid 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

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

• tipranavir

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

• tisotumab vedotin

  isoniazid 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.

• tofacitinib

  isoniazid increases levels of tofacitinib by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. No specific dose adjustment recommended when tofacitinib coadministered with potent CYP2C19 inhibitors; decrease tofacitinib dose if coadministered with both moderate CYP3A4 and potent CYP2C19 inhibitors .

• tolterodine

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

• toremifene

  isoniazid 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

  isoniazid and tramadol both increase serotonin levels. Use Caution/Monitor.

• trazodone

  isoniazid will increase the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  trazodone and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• triamcinolone acetonide injectable suspension

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

• triazolam

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

• trimipramine

  trimipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• ubrogepant

  isoniazid 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)

• umeclidinium bromide/vilanterol inhaled

  isoniazid 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

  isoniazid 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

  isoniazid 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.

• valoctocogene roxaparvovec

  isoniazid and valoctocogene roxaparvovec both increase Other (see comment). Use Caution/Monitor. Medications that may cause hepatotoxicity when combined with valoctogene roxaparvovec may potentiate the risk of elevated liver enzymes. Closely monitor these medications and consider alternative medications in case of potential drug interactions.

• vardenafil

  isoniazid will increase the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Vardenafil dose may need to be reduced if coadministered with moderate or strong CYP3A4 inhibitors

• venlafaxine

  venlafaxine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• verapamil

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

• vilanterol/fluticasone furoate inhaled

  isoniazid 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

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

• vincristine

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

• vincristine liposomal

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

• vinorelbine

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

• voriconazole

  isoniazid will increase the level or effect of voriconazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• warfarin

  isoniazid will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• zanubrutinib

  isoniazid will increase the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce zanubrutinib (a CYP3A4 substrate) to 80 mg PO BID to when coadministered with a moderate CYP3A4 inhibitor. Interrupt dose as recommended for adverse reactions. After discontinuing the CYP3A4 inhibitor, resume previous dose of zanubrutinib.

• zolmitriptan

  zolmitriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• zonisamide

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

Minor (77)

• acarbose

  isoniazid decreases effects of acarbose by unspecified interaction mechanism. Minor/Significance Unknown.

• acetaminophen

  isoniazid increases toxicity of acetaminophen by unknown mechanism. Minor/Significance Unknown.

• acetaminophen IV

  isoniazid increases toxicity of acetaminophen IV by unknown mechanism. Minor/Significance Unknown.

• acetaminophen rectal

  isoniazid increases toxicity of acetaminophen rectal by unknown mechanism. Minor/Significance Unknown.

• ambrisentan

  isoniazid will increase the level or effect of ambrisentan by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.
  
  isoniazid will increase the level or effect of ambrisentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• amitriptyline

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

• bazedoxifene/conjugated estrogens

  isoniazid will increase the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• budesonide

  budesonide decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• calcium acetate

  isoniazid decreases levels of calcium acetate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium carbonate

  isoniazid decreases levels of calcium carbonate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium chloride

  isoniazid decreases levels of calcium chloride by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium citrate

  isoniazid decreases levels of calcium citrate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium gluconate

  isoniazid decreases levels of calcium gluconate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• chlorpropamide

  isoniazid decreases effects of chlorpropamide by unspecified interaction mechanism. Minor/Significance Unknown.

• clomipramine

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

• conjugated estrogens

  isoniazid will increase the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• conjugated estrogens, vaginal

  isoniazid will increase the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• cortisone

  cortisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• deflazacort

  deflazacort decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• dexamethasone

  dexamethasone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• didanosine

  didanosine, isoniazid. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Enhanced risk of peripheral neuropathy.

• donepezil

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

• estradiol

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

• estrogens conjugated synthetic

  isoniazid will increase the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• estrogens esterified

  isoniazid will increase the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• estropipate

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

• ethanol

  isoniazid increases toxicity of ethanol by decreasing metabolism. Minor/Significance Unknown. Enhanced hepatotoxicity.

• ethotoin

  isoniazid increases levels of ethotoin by decreasing metabolism. Minor/Significance Unknown.

• eucalyptus

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

• fludrocortisone

  fludrocortisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• food

  food decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• fosphenytoin

  isoniazid increases levels of fosphenytoin by decreasing metabolism. Minor/Significance Unknown.

• ganaxolone

  isoniazid, 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.

• glimepiride

  isoniazid decreases effects of glimepiride by unspecified interaction mechanism. Minor/Significance Unknown.

• glipizide

  isoniazid decreases effects of glipizide by unspecified interaction mechanism. Minor/Significance Unknown.

• glyburide

  isoniazid decreases effects of glyburide by unspecified interaction mechanism. Minor/Significance Unknown.

• hydrocortisone

  hydrocortisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• imipramine

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

• insulin aspart

  isoniazid decreases effects of insulin aspart by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin detemir

  isoniazid decreases effects of insulin detemir by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin glargine

  isoniazid decreases effects of insulin glargine by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin glulisine

  isoniazid decreases effects of insulin glulisine by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin lispro

  isoniazid decreases effects of insulin lispro by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin NPH

  isoniazid decreases effects of insulin NPH by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin regular human

  isoniazid decreases effects of insulin regular human by unspecified interaction mechanism. Minor/Significance Unknown.

• ixazomib

  isoniazid, 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

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

• levoketoconazole

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

• mestranol

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

• methylprednisolone

  methylprednisolone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• miglitol

  isoniazid decreases effects of miglitol by unspecified interaction mechanism. Minor/Significance Unknown.

• montelukast

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

• nateglinide

  isoniazid decreases effects of nateglinide by unspecified interaction mechanism. Minor/Significance Unknown.

• niacin

  isoniazid decreases levels of niacin by pharmacodynamic antagonism. Minor/Significance Unknown.

• oxybutynin

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

• parecoxib

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

• phenytoin

  isoniazid increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

• pioglitazone

  isoniazid will increase the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  isoniazid decreases effects of pioglitazone by unspecified interaction mechanism. Minor/Significance Unknown.

• prednisolone

  prednisolone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• prednisone

  prednisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• primaquine

  primaquine, isoniazid. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Risk of hemolysis in G6PD deficient pts.

• pyrazinamide

  isoniazid, pyrazinamide. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive hepatotoxicity.

• pyridoxine

  isoniazid decreases levels of pyridoxine by unspecified interaction mechanism. Minor/Significance Unknown. If INH dose >10 mg/kg/day, supplement 50 100mg pyridoxine/day.

• pyridoxine (Antidote)

  isoniazid decreases levels of pyridoxine (Antidote) by unspecified interaction mechanism. Minor/Significance Unknown. If INH dose >10 mg/kg/day, supplement 50 100mg pyridoxine/day.

• rabeprazole

  isoniazid will increase the level or effect of rabeprazole by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.

• ramelteon

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

• repaglinide

  isoniazid decreases effects of repaglinide by unspecified interaction mechanism. Minor/Significance Unknown.

• rosiglitazone

  isoniazid decreases effects of rosiglitazone by unspecified interaction mechanism. Minor/Significance Unknown.

• sitagliptin

  isoniazid decreases effects of sitagliptin by unspecified interaction mechanism. Minor/Significance Unknown.

• tolazamide

  isoniazid decreases effects of tolazamide by unspecified interaction mechanism. Minor/Significance Unknown.

• tolbutamide

  isoniazid decreases effects of tolbutamide by unspecified interaction mechanism. Minor/Significance Unknown.

• triamcinolone acetonide injectable suspension

  triamcinolone acetonide injectable suspension decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• valproic acid

  isoniazid increases levels of valproic acid by decreasing metabolism. Minor/Significance Unknown.

• vildagliptin

  isoniazid decreases effects of vildagliptin by unspecified interaction mechanism. Minor/Significance Unknown.

• zaleplon

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

• ziprasidone

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

• zolpidem

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

• 5-HTP

  Monitor Closely (1)5-HTP and isoniazid both increase serotonin levels. Use Caution/Monitor.

• abemaciclib

  Monitor Closely (1)isoniazid 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.

• abrocitinib

  Monitor Closely (1)isoniazid will increase the level or effect of abrocitinib by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Start abrocitinib 50 mg qDay when coadministered with CYP2C19 inhibitors. If adequate response not achieved after 12 weeks, may increase to 100 mg qDay. Discontinue if inadequate response after dosage increase.

• acalabrutinib

  Serious - Use Alternative (1)isoniazid 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

  Minor (1)isoniazid decreases effects of acarbose by unspecified interaction mechanism. Minor/Significance Unknown.

• acetaminophen

  Monitor Closely (1)isoniazid will increase the level or effect of acetaminophen by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.Minor (1)isoniazid increases toxicity of acetaminophen by unknown mechanism. Minor/Significance Unknown.

• acetaminophen IV

  Monitor Closely (1)isoniazid will increase the level or effect of acetaminophen IV by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.Minor (1)isoniazid increases toxicity of acetaminophen IV by unknown mechanism. Minor/Significance Unknown.

• acetaminophen rectal

  Monitor Closely (1)isoniazid will increase the level or effect of acetaminophen rectal by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.Minor (1)isoniazid increases toxicity of acetaminophen rectal by unknown mechanism. Minor/Significance Unknown.

• ado-trastuzumab emtansine

  Serious - Use Alternative (1)isoniazid 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.

• alfentanil

  Serious - Use Alternative (1)isoniazid will increase the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Monitor for excessive CNS and respiratory depression

• alfuzosin

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

• almotriptan

  Monitor Closely (2)isoniazid will increase the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  almotriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• alosetron

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

• alprazolam

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

• aluminum hydroxide

  Monitor Closely (1)aluminum hydroxide decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• ambrisentan

  Minor (2)isoniazid will increase the level or effect of ambrisentan by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.
  
  isoniazid will increase the level or effect of ambrisentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• amifampridine

  Monitor Closely (1)isoniazid increases toxicity of amifampridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Amifampridine can cause seizures. Coadministration with drugs that lower seizure threshold may increase this risk.

• amiodarone

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

• amitriptyline

  Monitor Closely (2)amitriptyline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.
  
  isoniazid will increase the level or effect of amitriptyline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.Minor (1)isoniazid will increase the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• amoxapine

  Monitor Closely (1)amoxapine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• apalutamide

  Monitor Closely (1)isoniazid 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

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

• aripiprazole

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

• armodafinil

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

• artemether/lumefantrine

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

• atazanavir

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

• atogepant

  Monitor Closely (1)isoniazid 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.

• atorvastatin

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

• avanafil

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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 moderate CYP3A4 inhibitors. If unable to avoid, reduce avapritinib starting dose. See drug monograph Dosage Modifications.

• axitinib

  Serious - Use Alternative (1)isoniazid 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%.

• bazedoxifene/conjugated estrogens

  Minor (1)isoniazid will increase the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• bedaquiline

  Serious - Use Alternative (1)isoniazid 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

• belzutifan

  Monitor Closely (1)isoniazid will increase the level or effect of belzutifan by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Belzutifan is a CYP2C19 substrate. Coadministration with CYP2C19 inhibitors may increase incidence or severity of adverse effects. Monitor for anemia and hypoxia and reduce belzutifan dose as recommended.

• benzhydrocodone/acetaminophen

  Monitor Closely (1)isoniazid 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.

• bexarotene

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

• bortezomib

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

• bosentan

  Monitor Closely (1)isoniazid will increase the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• bosutinib

  Serious - Use Alternative (1)isoniazid 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.

• brentuximab vedotin

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

• brexpiprazole

  Monitor Closely (2)isoniazid 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.
  
  isoniazid will increase the level or effect of brexpiprazole by affecting hepatic enzyme CYP2D6 metabolism. Modify Therapy/Monitor Closely. Administer a quarter of brexpiprazole dose if coadministered with a moderate CYP2D6 inhibitor PLUS a strong/moderate CYP3A4 inhibitor.

• brigatinib

  Serious - Use Alternative (1)isoniazid 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.

• budesonide

  Monitor Closely (1)isoniazid will increase the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)budesonide decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• buprenorphine subdermal implant

  Monitor Closely (1)isoniazid 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, long-acting injection

  Monitor Closely (1)isoniazid 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.

• buspirone

  Monitor Closely (2)isoniazid will increase the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  buspirone and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• cabazitaxel

  Serious - Use Alternative (1)isoniazid will increase the level or effect of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of cabazitaxel with strong CYP3A4 inhibitors should be avoided.

• cabozantinib

  Serious - Use Alternative (1)isoniazid 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)isoniazid, 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.

• calcium acetate

  Minor (1)isoniazid decreases levels of calcium acetate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium carbonate

  Monitor Closely (1)calcium carbonate decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.Minor (1)isoniazid decreases levels of calcium carbonate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium chloride

  Minor (1)isoniazid decreases levels of calcium chloride by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium citrate

  Minor (1)isoniazid decreases levels of calcium citrate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• calcium gluconate

  Minor (1)isoniazid decreases levels of calcium gluconate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• cannabidiol

  Monitor Closely (2)isoniazid 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.
  
  isoniazid will increase the level or effect of cannabidiol by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider reducing the cannabidiol dose when coadministered with a strong CYP2C19 inhibitor.

• carbamazepine

  Monitor Closely (1)isoniazid 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

  Monitor Closely (1)isoniazid 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.

• ceritinib

  Serious - Use Alternative (1)isoniazid 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.

• cevimeline

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

• chlorpropamide

  Minor (1)isoniazid decreases effects of chlorpropamide by unspecified interaction mechanism. Minor/Significance Unknown.

• cilostazol

  Monitor Closely (1)isoniazid will increase the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)isoniazid increases toxicity of cilostazol by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. Decrease cilostazol dose by 50%; serum levels of 3,4-dehydrocilostazol (active metabolite) increased by strong CYP2C19 inhibitors.

• cimetidine

  Monitor Closely (1)isoniazid will increase the level or effect of cimetidine by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• cinacalcet

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

• citalopram

  Monitor Closely (1)isoniazid will increase the level or effect of citalopram by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Citalopram 20 mg/day is the maximum recommended dose for patients taking CYP2C19 inhibitors because of the risk of QT prolongation.

• clarithromycin

  Monitor Closely (1)isoniazid will increase the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• clobazam

  Monitor Closely (1)isoniazid will increase the level or effect of clobazam by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Dosage adjustment may be required; CYP2C19 inhibitors may result in increased exposure to N-desmethylclobazam (active metabolite).

• clomipramine

  Monitor Closely (1)clomipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.Minor (1)isoniazid will increase the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• clopidogrel

  Monitor Closely (1)isoniazid will decrease the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Inhibition of CYP3A4 will reduce clopidogrel bioactivationSerious - Use Alternative (1)isoniazid decreases effects of clopidogrel by decreasing metabolism. Avoid or Use Alternate Drug. Cytochrome P450 2C19 inhibitors decrease the conversion of clopidogrel to its active form.

• clorazepate

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

• clozapine

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

• cobicistat

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

• cobimetinib

  Contraindicated (1)isoniazid 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 topical

  Monitor Closely (1)cocaine topical and isoniazid both increase serotonin levels. Use Caution/Monitor.

• codeine

  Monitor Closely (1)isoniazid decreases effects of codeine by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor. Prevents conversion of codeine to its active metabolite morphine.

• conivaptan

  Contraindicated (1)isoniazid 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.

• conjugated estrogens

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

• conjugated estrogens, vaginal

  Minor (1)isoniazid will increase the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• copanlisib

  Serious - Use Alternative (1)isoniazid 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 (1)isoniazid will increase the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)cortisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• crizotinib

  Monitor Closely (1)isoniazid increases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use of strong CYP3A inhibitors should be avoided. .

• cycloserine

  Monitor Closely (1)isoniazid increases toxicity of cycloserine by decreasing metabolism. Use Caution/Monitor. Enhanced CNS toxicity; risk of seizure.

• dabrafenib

  Serious - Use Alternative (1)isoniazid increases levels of dabrafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• dapsone

  Monitor Closely (2)isoniazid will increase the level or effect of dapsone by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.
  
  isoniazid will increase the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• daridorexant

  Monitor Closely (1)isoniazid will increase the level or effect of daridorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Daridorexant dose should not exceed 25 mg per night when coadministered with moderate CYP3A4 inhibitors.

• darifenacin

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

• darunavir

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

• dasatinib

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

• deflazacort

  Monitor Closely (1)isoniazid 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.Minor (1)deflazacort decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• desipramine

  Monitor Closely (1)desipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• desvenlafaxine

  Serious - Use Alternative (1)isoniazid and desvenlafaxine both increase serotonin levels. Avoid or Use Alternate Drug.

• dexamethasone

  Monitor Closely (1)isoniazid will increase the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)dexamethasone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• dexfenfluramine

  Monitor Closely (1)dexfenfluramine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• dextroamphetamine

  Monitor Closely (1)dextroamphetamine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• dextromethorphan

  Monitor Closely (1)dextromethorphan and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• diazepam

  Monitor Closely (2)isoniazid will increase the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  isoniazid will increase the level or effect of diazepam by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• diazepam intranasal

  Monitor Closely (2)isoniazid will increase the level or effect of diazepam intranasal by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Strong or moderate CYP2C19 inhibitors may decrease rate of diazepam elimination, thereby increasing adverse reactions to diazepam.
  
  isoniazid 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.

• dichlorphenamide

  Monitor Closely (1)dichlorphenamide, isoniazid. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Both drugs can cause metabolic acidosis.

• didanosine

  Minor (1)didanosine, isoniazid. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Enhanced risk of peripheral neuropathy.

• dienogest/estradiol valerate

  Monitor Closely (1)isoniazid will increase the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor for potential adverse effects such as nausea, irregular uterine bleeding, breast tenderness and headache.

• dihydroergotamine

  Contraindicated (1)isoniazid will increase the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Monitor Closely (1)dihydroergotamine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• dihydroergotamine intranasal

  Contraindicated (1)isoniazid will increase the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.Monitor Closely (1)dihydroergotamine intranasal and isoniazid both increase serotonin levels. Use Caution/Monitor.

• disopyramide

  Monitor Closely (1)isoniazid will increase the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• disulfiram

  Monitor Closely (2)disulfiram will increase the level or effect of isoniazid by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.
  
  isoniazid increases toxicity of disulfiram by decreasing metabolism. Use Caution/Monitor. Enhanced CNS toxicity.

• docetaxel

  Monitor Closely (1)isoniazid will increase the level or effect of docetaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• donepezil

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

• doravirine

  Monitor Closely (1)isoniazid 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)doxepin and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• doxorubicin

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

• doxorubicin liposomal

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

• dronabinol

  Monitor Closely (1)isoniazid will increase the level or effect of dronabinol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dronabinol is a CYP3A4 substrate.

• dronedarone

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

• duloxetine

  Monitor Closely (1)duloxetine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• dutasteride

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

• efavirenz

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

• elacestrant

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

• elagolix

  Monitor Closely (1)isoniazid will increase the level or effect of elagolix by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of elagolix 200 mg BID with strong CYP3A inhibitors for >1 month is not recommended. Limit elagolix dose to 150 mg qDay and CYP3A inhibitor duration of use to 6 months if coadministered.

• eletriptan

  Monitor Closely (2)isoniazid will increase the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  eletriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• eliglustat

  Contraindicated (2)isoniazid 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
  
  isoniazid 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.

• eluxadoline

  Monitor Closely (1)isoniazid increases levels of eluxadoline by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. As a precautionary measure due to incomplete information on the metabolism of eluxadoline, use caution when coadministered with strong CYP2C19 inhibitors.

• elvitegravir

  Monitor Closely (1)isoniazid increases levels of elvitegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Elvitegravir is a CYP3A4 substrate; if coadministered with strong CYP3A4 inhibitors may increase levels.

• elvitegravir/cobicistat/emtricitabine/tenofovir DF

  Monitor Closely (1)isoniazid will increase the level or effect of elvitegravir/cobicistat/emtricitabine/tenofovir DF by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• encorafenib

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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.

• entrectinib

  Serious - Use Alternative (1)isoniazid will increase the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of moderate CYP3A4 inhibitors with entrectinib, a CYP3A4 substrate. If coadministration unavoidable, reduce dose to 200 mg/day for patients aged 12 y or older with BSA >1.50m2. Resume previous entrectinib dose after discontinuing moderate CYP3A inhibitor for 3-5 elimination half-lives.

• eplerenone

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

• erdafitinib

  Serious - Use Alternative (1)isoniazid 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.

• ergotamine

  Monitor Closely (1)ergotamine and isoniazid both increase serotonin levels. Use Caution/Monitor.Serious - Use Alternative (1)isoniazid will increase the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erlotinib

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

• erythromycin base

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

• erythromycin ethylsuccinate

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

• erythromycin lactobionate

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

• erythromycin stearate

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

• escitalopram

  Monitor Closely (2)isoniazid will increase the level or effect of escitalopram by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  escitalopram and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• esomeprazole

  Serious - Use Alternative (1)isoniazid will increase the level or effect of esomeprazole by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

• estradiol

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

• estradiol vaginal

  Monitor Closely (1)isoniazid 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

  Minor (1)isoniazid will increase the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• estrogens esterified

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

• estropipate

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

• ethanol

  Monitor Closely (1)isoniazid will increase the level or effect of ethanol by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor. Generally avoid; increased risk of hepatotoxicityMinor (1)isoniazid increases toxicity of ethanol by decreasing metabolism. Minor/Significance Unknown. Enhanced hepatotoxicity.

• ethionamide

  Monitor Closely (1)ethionamide increases levels of isoniazid by unspecified interaction mechanism. Use Caution/Monitor.

• ethotoin

  Minor (1)isoniazid increases levels of ethotoin by decreasing metabolism. Minor/Significance Unknown.

• etonogestrel

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

• etoposide

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

• etravirine

  Monitor Closely (1)isoniazid will increase the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)isoniazid will increase the level or effect of etravirine by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

• eucalyptus

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

• everolimus

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

• fedratinib

  Serious - Use Alternative (2)isoniazid will increase the level or effect of fedratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  isoniazid 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.

• felodipine

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

• fenfluramine

  Monitor Closely (1)fenfluramine and isoniazid both increase serotonin levels. Use Caution/Monitor.

• fentanyl

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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)isoniazid 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)isoniazid 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)isoniazid will increase the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fexinidazole

  Serious - Use Alternative (1)isoniazid 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.

• finasteride

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

• finerenone

  Monitor Closely (1)isoniazid will increase the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor serum potassium during initiation and dosage adjustment of either finererone or moderate CYP3A4 inhibitors. Adjust finererone dosage as needed.

• flibanserin

  Contraindicated (1)isoniazid 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.Monitor Closely (1)isoniazid will increase the level or effect of flibanserin by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Coadministration of flibanserin with strong CYP2C19 inhibitors may increase flibanserin exposure and increase the risk of hypotension, syncope, and CNS depression.

• fludrocortisone

  Monitor Closely (1)isoniazid will increase the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)fludrocortisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• fluoxetine

  Monitor Closely (1)fluoxetine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• fluticasone furoate

  Monitor Closely (1)isoniazid 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)isoniazid 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)isoniazid 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.

• fluvoxamine

  Monitor Closely (1)fluvoxamine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• food

  Minor (1)food decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• fosamprenavir

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

• fosaprepitant

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

• fosphenytoin

  Minor (1)isoniazid increases levels of fosphenytoin by decreasing metabolism. Minor/Significance Unknown.

• frovatriptan

  Monitor Closely (1)frovatriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• galantamine

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

• ganaxolone

  Minor (1)isoniazid, 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.

• gefitinib

  Monitor Closely (1)isoniazid 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.

• gepirone

  Monitor Closely (2)gepirone and isoniazid both increase serotonin levels. Use Caution/Monitor. Monitor for symptoms of serotonin syndrome when gepirone is used gepirone with other drugs that may affect the serotonergic neurotransmitter systems. If serotonin syndrome occurs, consider discontinue gepirone and/or concomitant serotonergic drug.
  
  isoniazid will increase the level or effect of gepirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce gepirone dose by 50% when used concomitantly with a moderate CYP3A4 inhibitor.

• gilteritinib

  Serious - Use Alternative (1)isoniazid 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.

• glasdegib

  Serious - Use Alternative (1)isoniazid 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)isoniazid will increase the level or effect of glecaprevir/pibrentasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• glimepiride

  Minor (1)isoniazid decreases effects of glimepiride by unspecified interaction mechanism. Minor/Significance Unknown.

• glipizide

  Minor (1)isoniazid decreases effects of glipizide by unspecified interaction mechanism. Minor/Significance Unknown.

• glyburide

  Minor (1)isoniazid decreases effects of glyburide by unspecified interaction mechanism. Minor/Significance Unknown.

• green tea

  Monitor Closely (1)green tea, isoniazid. Other (see comment). Use Caution/Monitor. Comment: Avoid combination or excessive consumption of green tea. Combination may increase risk of cardiac arrhythmias or severe hypertension can occur due to caffeine component of green tea.

• guanfacine

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

• hydrocodone

  Monitor Closely (1)isoniazid 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 (1)isoniazid will increase the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)hydrocortisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• hydroxyprogesterone caproate (DSC)

  Monitor Closely (1)isoniazid will increase the level or effect of hydroxyprogesterone caproate (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ibrutinib

  Serious - Use Alternative (1)isoniazid 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 (1)isoniazid 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

• iloperidone

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

• imatinib

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

• imipramine

  Monitor Closely (2)imipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.
  
  isoniazid will increase the level or effect of imipramine by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.Minor (1)isoniazid will increase the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• indinavir

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

• infigratinib

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

• insulin aspart

  Minor (1)isoniazid decreases effects of insulin aspart by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin degludec

  Monitor Closely (1)isoniazid decreases effects of insulin degludec by pharmacodynamic antagonism. Use Caution/Monitor. Isoniazid may increase blood glucose (rare).

• insulin degludec/insulin aspart

  Monitor Closely (1)isoniazid decreases effects of insulin degludec/insulin aspart by pharmacodynamic antagonism. Use Caution/Monitor. Isoniazid may increase blood glucose (rare).

• insulin detemir

  Minor (1)isoniazid decreases effects of insulin detemir by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin glargine

  Minor (1)isoniazid decreases effects of insulin glargine by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin glulisine

  Minor (1)isoniazid decreases effects of insulin glulisine by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin inhaled

  Monitor Closely (1)isoniazid decreases effects of insulin inhaled by pharmacodynamic antagonism. Use Caution/Monitor. Isoniazid may increase blood glucose (rare).

• insulin lispro

  Minor (1)isoniazid decreases effects of insulin lispro by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin NPH

  Minor (1)isoniazid decreases effects of insulin NPH by unspecified interaction mechanism. Minor/Significance Unknown.

• insulin regular human

  Minor (1)isoniazid decreases effects of insulin regular human by unspecified interaction mechanism. Minor/Significance Unknown.

• irinotecan

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

• irinotecan liposomal

  Serious - Use Alternative (1)isoniazid 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)isoniazid will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• isocarboxazid

  Serious - Use Alternative (1)isocarboxazid and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug.

• isradipine

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

• istradefylline

  Monitor Closely (1)isoniazid 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)isoniazid decreases levels of itraconazole by unspecified interaction mechanism. Use Caution/Monitor.

• ivabradine

  Contraindicated (1)isoniazid 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 (1)isoniazid 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.

• ixabepilone

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

• ixazomib

  Minor (1)isoniazid, 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

  Contraindicated (1)isoniazid decreases levels of ketoconazole by unspecified interaction mechanism. Contraindicated.Minor (1)isoniazid will increase the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• L-tryptophan

  Monitor Closely (1)isoniazid and L-tryptophan both increase serotonin levels. Use Caution/Monitor.

• lacosamide

  Monitor Closely (1)isoniazid increases levels of lacosamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider decreasing lacosamide dose when coadministered with strong CYP3A4 inhibitors.

• lansoprazole

  Monitor Closely (1)isoniazid will increase the level or effect of lansoprazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• lapatinib

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

• lefamulin

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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.

• levamlodipine

  Monitor Closely (1)isoniazid will increase the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with moderate and strong CYP3A inhibitors results in increased systemic exposure to amlodipine and may require dose reduction. Monitor for symptoms of hypotension and edema when amlodipine is coadministered with CYP3A inhibitors to determine the need for dose adjustment.

• levodopa inhaled

  Monitor Closely (1)isoniazid decreases effects of levodopa inhaled by altering metabolism. Use Caution/Monitor. Isoniazid may inhibit dopa-decarboxylase in the brain; thereby, preventing conversion of levodopa to active dopamine.

• levoketoconazole

  Contraindicated (1)isoniazid decreases levels of levoketoconazole by unspecified interaction mechanism. Contraindicated.Minor (1)isoniazid will increase the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• levomilnacipran

  Monitor Closely (2)levomilnacipran and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.
  
  isoniazid 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 oral/ethinylestradiol/ferrous bisglycinate

  Monitor Closely (1)isoniazid will increase the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with CYP3A4 inhibitors may increase the plasma hormone concentrations. Use of a nonhormonal contraceptive is recommended.

• linezolid

  Serious - Use Alternative (1)linezolid and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug. Linezolid may increase serotonin as a result of MAO-A inhibition. If linezolid must be administered, discontinue serotonergic drug immediately and monitor for CNS toxicity. Serotonergic therapy may be resumed 24 hours after last linezolid dose or after 2 weeks of monitoring, whichever comes first.

• lithium

  Monitor Closely (1)isoniazid and lithium both increase serotonin levels. Use Caution/Monitor.

• lofepramine

  Monitor Closely (1)lofepramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• lomitapide

  Contraindicated (1)isoniazid increases levels of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Increases lomitapide levels several folds.

• lonafarnib

  Contraindicated (1)isoniazid 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.

• lopinavir

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

• loratadine

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

• lorcaserin

  Serious - Use Alternative (1)isoniazid and lorcaserin both increase serotonin levels. Avoid or Use Alternate Drug.

• lorlatinib

  Serious - Use Alternative (1)isoniazid 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.

• lovastatin

  Contraindicated (1)isoniazid 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

• lsd

  Monitor Closely (1)isoniazid and lsd both increase serotonin levels. Use Caution/Monitor.

• lumacaftor/ivacaftor

  Monitor Closely (1)isoniazid 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)isoniazid will increase the level or effect of lumateperone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce lumateperone dose to 21 mg/day if coadministered with moderate CYP3A4 inhibitors.

• lumefantrine

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

• lurasidone

  Contraindicated (1)isoniazid 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)isoniazid 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)isoniazid 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

• maprotiline

  Monitor Closely (1)maprotiline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• maraviroc

  Monitor Closely (1)isoniazid 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

• mavacamten

  Contraindicated (1)isoniazid will increase the level or effect of mavacamten by affecting hepatic enzyme CYP2C19 metabolism. Contraindicated. Strong or moderate CYP2C19 inhibitors may increase mavacamten systemic exposure, resulting in heart failure due to systolic dysfunction. Monitor Closely (1)isoniazid will increase the level or effect of mavacamten by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Inititiation of moderate CYP3A4 inhibitors may require decreased mavacamten dose.

• medroxyprogesterone

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

• mefloquine

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

• meperidine

  Monitor Closely (1)isoniazid and meperidine both increase serotonin levels. Modify Therapy/Monitor Closely.

• mestranol

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

• metformin

  Monitor Closely (1)isoniazid decreases effects of metformin by unspecified interaction mechanism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.

• methadone

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

• methylene blue

  Serious - Use Alternative (1)methylene blue and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug. Methylene blue and isoniazid may increase serotonin as a result of MAO-A inhibition. If methylene blue must be administered, discontinue isoniazid immediately and monitor for CNS toxicity. Isoniazid may be resumed 24 hours after last methylene blue dose or after 2 weeks of monitoring, whichever comes first.

• methylprednisolone

  Monitor Closely (1)isoniazid will increase the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)methylprednisolone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• metronidazole

  Monitor Closely (1)metronidazole will increase the level or effect of isoniazid by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• midazolam

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

• midazolam intranasal

  Serious - Use Alternative (1)isoniazid will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of moderate CYP3A4 inhibitors with midazolam intranasal causes higher midazolam systemic exposure, which may prolong sedation.

• midostaurin

  Serious - Use Alternative (1)isoniazid 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.

• miglitol

  Minor (1)isoniazid decreases effects of miglitol by unspecified interaction mechanism. Minor/Significance Unknown.

• milnacipran

  Monitor Closely (1)milnacipran and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• mipomersen

  Monitor Closely (1)mipomersen, isoniazid. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Both drugs have potential to increase hepatic enzymes; monitor LFTs.

• mirtazapine

  Monitor Closely (1)isoniazid and mirtazapine both increase serotonin levels. Use Caution/Monitor.Serious - Use Alternative (1)isoniazid will increase the level or effect of mirtazapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• mobocertinib

  Serious - Use Alternative (1)isoniazid will increase the level or effect of mobocertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If use of moderate CYP3A4 inhibitor unavoidable, reduce mobocertinib dose by ~50% (eg, 160 to 80 mg); closely monitor QTc interval.

• montelukast

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

• morphine

  Monitor Closely (1)isoniazid and morphine both increase serotonin levels. Use Caution/Monitor.

• naldemedine

  Monitor Closely (1)isoniazid 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.

• naloxegol

  Contraindicated (1)isoniazid 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

• naratriptan

  Monitor Closely (1)naratriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• nateglinide

  Minor (1)isoniazid decreases effects of nateglinide by unspecified interaction mechanism. Minor/Significance Unknown.

• nefazodone

  Monitor Closely (1)nefazodone and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• nelfinavir

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

• neratinib

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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

• niacin

  Minor (1)isoniazid decreases levels of niacin by pharmacodynamic antagonism. Minor/Significance Unknown.

• nicardipine

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

• nifedipine

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

• nilotinib

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

• nimodipine

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

• nisoldipine

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

• nitrendipine

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

• norgestrel

  Monitor Closely (1)isoniazid will increase the level or effect of norgestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inhibitors may increase systemic concentration of norgestrel, which may increase risk for adverse effects

• nortriptyline

  Monitor Closely (1)nortriptyline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• olaparib

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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.
  
  isoniazid 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.

• omaveloxolone

  Serious - Use Alternative (1)isoniazid will increase the level or effect of omaveloxolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unavoidable, reduce omaveloxolone dose to 100 mg/day. Closely monitor for adverse effects. If adverse effects emerge, further reduce to 50 mg/day.

• omeprazole

  Serious - Use Alternative (1)isoniazid will increase the level or effect of omeprazole by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug.

• ondansetron

  Monitor Closely (1)isoniazid will increase the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP-450 inhibitors may decrease clearance of ondansetron. However, no dosage adjustment for ondansetron is recommended

• osilodrostat

  Monitor Closely (1)isoniazid 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)isoniazid 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 (2)isoniazid increases levels of ospemifene by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.
  
  isoniazid increases levels of ospemifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• oxybutynin

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

• oxycodone

  Serious - Use Alternative (1)isoniazid 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.

• paclitaxel

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

• paclitaxel protein bound

  Monitor Closely (1)isoniazid will increase the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• pacritinib

  Contraindicated (1)isoniazid will increase the level or effect of pacritinib by affecting hepatic enzyme CYP2E1 metabolism. Contraindicated.Serious - Use Alternative (1)isoniazid 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)isoniazid 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.

• palovarotene

  Monitor Closely (1)isoniazid will increase the level or effect of palovarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Avoid coadministration of palovarotene, a CYP3A substrate, with moderate CYP3A inhibitors. If unavoidable, reduce palovarotene dose by 50%.

• panobinostat

  Monitor Closely (1)isoniazid 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)isoniazid will increase the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paroxetine

  Monitor Closely (1)paroxetine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• pazopanib

  Monitor Closely (1)isoniazid will increase the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid coadministration of pazopanib with strong CYP3A4 inhibitors if possible; if must coadminister, decrease pazopanib dose to 400 mg/day

• pemigatinib

  Serious - Use Alternative (1)isoniazid 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.

• pentazocine

  Monitor Closely (1)isoniazid and pentazocine both increase serotonin levels. Use Caution/Monitor.

• pexidartinib

  Serious - Use Alternative (2)isoniazid 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.
  
  isoniazid and pexidartinib both increase inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug. Pexidartinib can cause hepatotoxicity. Avoid coadministration of pexidartinib with other products know to cause hepatoxicity.

• phenelzine

  Serious - Use Alternative (1)phenelzine and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug.

• phenytoin

  Minor (1)isoniazid increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

• pimavanserin

  Serious - Use Alternative (1)isoniazid 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

  Monitor Closely (1)isoniazid will increase the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)isoniazid increases levels of pimozide by decreasing metabolism. Contraindicated. Risk of QT interval prolongation.

• pioglitazone

  Minor (2)isoniazid will increase the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
  
  isoniazid decreases effects of pioglitazone by unspecified interaction mechanism. Minor/Significance Unknown.

• polatuzumab vedotin

  Monitor Closely (1)isoniazid 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 (1)isoniazid increases levels of pomalidomide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• ponatinib

  Serious - Use Alternative (1)isoniazid 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

  Serious - Use Alternative (1)isoniazid will increase the level or effect of pralsetinib by affecting hepatic enzyme CYP2E1 metabolism. Avoid or Use Alternate Drug.

• prednisolone

  Monitor Closely (1)isoniazid will increase the level or effect of prednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)prednisolone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• prednisone

  Monitor Closely (1)isoniazid will increase the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)prednisone decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• pretomanid

  Serious - Use Alternative (1)isoniazid, pretomanid. Either increases toxicity of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Pretomanid regimen associated with hepatotoxicity. Avoid alcohol and hepatotoxic agents, including herbal supplements and drugs other than bedaquiline and linezolid.

• primaquine

  Minor (1)primaquine, isoniazid. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Risk of hemolysis in G6PD deficient pts.

• propafenone

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

• protriptyline

  Monitor Closely (1)protriptyline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• pyrazinamide

  Minor (1)isoniazid, pyrazinamide. Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown. Additive hepatotoxicity.

• pyridoxine

  Minor (1)isoniazid decreases levels of pyridoxine by unspecified interaction mechanism. Minor/Significance Unknown. If INH dose >10 mg/kg/day, supplement 50 100mg pyridoxine/day.

• pyridoxine (Antidote)

  Minor (1)isoniazid decreases levels of pyridoxine (Antidote) by unspecified interaction mechanism. Minor/Significance Unknown. If INH dose >10 mg/kg/day, supplement 50 100mg pyridoxine/day.

• quetiapine

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

• quinidine

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

• quinine

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

• rabeprazole

  Minor (1)isoniazid will increase the level or effect of rabeprazole by affecting hepatic enzyme CYP2C19 metabolism. Minor/Significance Unknown.

• ramelteon

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

• ranolazine

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

• rasagiline

  Monitor Closely (1)rasagiline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• red yeast rice

  Serious - Use Alternative (1)isoniazid 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)isoniazid, 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)isoniazid will increase the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)isoniazid decreases effects of repaglinide by unspecified interaction mechanism. Minor/Significance Unknown.

• rifampin

  Serious - Use Alternative (1)rifampin increases toxicity of isoniazid by increasing metabolism. Avoid or Use Alternate Drug. Rifampin enhances the metabolism of isoniazid to hepatotoxic metabolites.

• rilpivirine

  Monitor Closely (1)isoniazid increases levels of rilpivirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• rimegepant

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

• riociguat

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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.

• ritonavir

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

• rizatriptan

  Monitor Closely (1)rizatriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• romidepsin

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

• rosiglitazone

  Minor (1)isoniazid decreases effects of rosiglitazone by unspecified interaction mechanism. Minor/Significance Unknown.

• ruxolitinib

  Serious - Use Alternative (1)isoniazid 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)isoniazid 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

• safinamide

  Monitor Closely (1)isoniazid, safinamide. Either increases toxicity of the other by serotonin levels. Modify Therapy/Monitor Closely. Monitor for hypertension and reaction to dietary tyramine in patients treated concomitantly with isoniazid and safinamide.

• SAMe

  Monitor Closely (1)isoniazid and SAMe both increase serotonin levels. Use Caution/Monitor.

• saquinavir

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

• saxagliptin

  Monitor Closely (1)isoniazid will increase the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limit saxagliptin dose to 2.5 mg/day when coadministered with strong CYP3A4 inhibitors

• selegiline

  Monitor Closely (1)selegiline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• selegiline transdermal

  Monitor Closely (1)selegiline transdermal and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• selumetinib

  Serious - Use Alternative (1)isoniazid 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)sertraline and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• sevoflurane

  Monitor Closely (1)isoniazid will increase the level or effect of sevoflurane by affecting hepatic enzyme CYP2E1 metabolism. Use Caution/Monitor.

• sildenafil

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

• silodosin

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

• simvastatin

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

• siponimod

  Serious - Use Alternative (1)isoniazid 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

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

• sitagliptin

  Minor (1)isoniazid decreases effects of sitagliptin by unspecified interaction mechanism. Minor/Significance Unknown.

• sodium bicarbonate

  Monitor Closely (1)sodium bicarbonate decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• sodium citrate/citric acid

  Monitor Closely (1)sodium citrate/citric acid decreases levels of isoniazid by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.

• sodium picosulfate/magnesium oxide/anhydrous citric acid

  Monitor Closely (1)isoniazid decreases effects of sodium picosulfate/magnesium oxide/anhydrous citric acid by altering metabolism. Use Caution/Monitor. Coadministration with antibiotics decreases efficacy by altering colonic bacterial flora needed to convert sodium picosulfate to active drug.

• sodium sulfate/?magnesium sulfate/potassium chloride

  Monitor Closely (1)sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of isoniazid by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• sodium sulfate/potassium sulfate/magnesium sulfate

  Monitor Closely (1)sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of isoniazid by Other (see comment). Use Caution/Monitor. Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

• solifenacin

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

• sonidegib

  Serious - Use Alternative (1)isoniazid 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.

• St John's Wort

  Monitor Closely (1)isoniazid and St John's Wort both increase serotonin levels. Modify Therapy/Monitor Closely.

• sufentanil

  Monitor Closely (1)isoniazid will increase the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

• sufentanil SL

  Monitor Closely (1)isoniazid 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.

• sumatriptan

  Monitor Closely (1)sumatriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• sumatriptan intranasal

  Monitor Closely (1)sumatriptan intranasal and isoniazid both increase serotonin levels. Use Caution/Monitor.

• sunitinib

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

• suvorexant

  Serious - Use Alternative (1)isoniazid 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 (1)isoniazid will increase the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tadalafil

  Monitor Closely (1)isoniazid will increase the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For ED limit tadalafil to max of 2.5 mg/day (for daily use) or 10 mg dose every 72 hr (for use as needed). Avoid concurrent use of tadalafil for pulmonary HTN in patients taking strong CYP3A4 inhibitors.

• tamoxifen

  Monitor Closely (1)isoniazid, tamoxifen. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. CYP3A4 inhibition decreases metabolism of tamoxifen to N-desmethyl tamoxifen (active metabolite with similar biologic activity).

• tamsulosin

  Monitor Closely (1)isoniazid increases levels of tamsulosin by affecting hepatic enzyme CYP2D6 metabolism. Use Caution/Monitor.Serious - Use Alternative (1)isoniazid increases levels of tamsulosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• tasimelteon

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

• tazemetostat

  Serious - Use Alternative (1)isoniazid will increase the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of tazemetostat with moderate CYP3A4 inhibitors. If coadministration is unavoidable, reduce tazemetostat current dose (see drug monograph Dosage Modifications).

• temsirolimus

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

• terbinafine

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

• tezacaftor

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

• tipranavir

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

• tisotumab vedotin

  Monitor Closely (1)isoniazid 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.

• tofacitinib

  Monitor Closely (1)isoniazid increases levels of tofacitinib by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. No specific dose adjustment recommended when tofacitinib coadministered with potent CYP2C19 inhibitors; decrease tofacitinib dose if coadministered with both moderate CYP3A4 and potent CYP2C19 inhibitors .Serious - Use Alternative (1)isoniazid 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

  Minor (1)isoniazid decreases effects of tolazamide by unspecified interaction mechanism. Minor/Significance Unknown.

• tolbutamide

  Minor (1)isoniazid decreases effects of tolbutamide by unspecified interaction mechanism. Minor/Significance Unknown.

• tolterodine

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

• tolvaptan

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

• toremifene

  Monitor Closely (1)isoniazid 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)isoniazid 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)isoniazid and tramadol both increase serotonin levels. Use Caution/Monitor.

• tranylcypromine

  Serious - Use Alternative (1)tranylcypromine and isoniazid both increase serotonin levels. Avoid or Use Alternate Drug.

• trazodone

  Monitor Closely (2)isoniazid will increase the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  trazodone and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• triamcinolone acetonide injectable suspension

  Monitor Closely (1)isoniazid will increase the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.Minor (1)triamcinolone acetonide injectable suspension decreases effects of isoniazid by unknown mechanism. Minor/Significance Unknown.

• triazolam

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

• trimipramine

  Monitor Closely (1)trimipramine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• ubrogepant

  Monitor Closely (1)isoniazid 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)

• umeclidinium bromide/vilanterol inhaled

  Monitor Closely (1)isoniazid 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)isoniazid 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 (1)isoniazid 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.

• valoctocogene roxaparvovec

  Monitor Closely (1)isoniazid and valoctocogene roxaparvovec both increase Other (see comment). Use Caution/Monitor. Medications that may cause hepatotoxicity when combined with valoctogene roxaparvovec may potentiate the risk of elevated liver enzymes. Closely monitor these medications and consider alternative medications in case of potential drug interactions.

• valproic acid

  Minor (1)isoniazid increases levels of valproic acid by decreasing metabolism. Minor/Significance Unknown.

• vardenafil

  Monitor Closely (1)isoniazid will increase the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Vardenafil dose may need to be reduced if coadministered with moderate or strong CYP3A4 inhibitors

• vemurafenib

  Serious - Use Alternative (1)isoniazid increases levels of vemurafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• venetoclax

  Contraindicated (1)isoniazid 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)venlafaxine and isoniazid both increase serotonin levels. Modify Therapy/Monitor Closely.

• verapamil

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

• vilanterol/fluticasone furoate inhaled

  Monitor Closely (1)isoniazid 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 (2)isoniazid, vilazodone. Either increases toxicity of the other by serotonin levels. Avoid or Use Alternate Drug. Concomitant therapy should be discontinued immediately if signs or symptoms of serotonin syndrome emerge and supportive symptomatic treatment should be initiated. .
  
  isoniazid 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.

• vildagliptin

  Minor (1)isoniazid decreases effects of vildagliptin by unspecified interaction mechanism. Minor/Significance Unknown.

• vinblastine

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

• vincristine

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

• vincristine liposomal

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

• vinorelbine

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

• voclosporin

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

• vorapaxar

  Serious - Use Alternative (1)isoniazid increases levels of vorapaxar by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• voriconazole

  Monitor Closely (1)isoniazid will increase the level or effect of voriconazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

• warfarin

  Monitor Closely (1)isoniazid will increase the level or effect of warfarin by Other (see comment). Use Caution/Monitor. Warfarin's less potent R-enantiomer is metabolized in part by CYP3A4 (and also CYP1A2 and CYP2C19). Monitor INR more frequently if coadministered with inhibitors of these isoenzymes and adjust warfarin dose if needed.

• zaleplon

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

• zanubrutinib

  Monitor Closely (1)isoniazid will increase the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce zanubrutinib (a CYP3A4 substrate) to 80 mg PO BID to when coadministered with a moderate CYP3A4 inhibitor. Interrupt dose as recommended for adverse reactions. After discontinuing the CYP3A4 inhibitor, resume previous dose of zanubrutinib.

• ziprasidone

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

• zolmitriptan

  Monitor Closely (1)zolmitriptan and isoniazid both increase serotonin levels. Use Caution/Monitor.

• zolpidem

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

• zonisamide

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