isoniazid (Rx)

Brand and Other Names:
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablets

  • 50mg
  • 100mg
  • 300mg

oral syrup

  • 50mg/5mL

injectable solution

  • 100mg/mL

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

Dosage Forms & Strengths

tablets

  • 50mg
  • 100mg
  • 300mg

oral syrup

  • 50mg/5mL

injectable solution

  • 100mg/mL

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

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Interactions

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            Contraindicated (17)

            • 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.

            • 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.

            • 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

            • 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 (98)

            • 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.

            • 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.

            • 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.

            • 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

            • 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).

            • tizanidine

              isoniazid will increase the level or effect of tizanidine by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug.

            • 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.

            • voxelotor

              isoniazid will increase the level or effect of voxelotor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor is primarily metabolized by CYP3A4. Avoid coadministration with strong CYP3A4 inhibitors. If unable to avoid coadministration, reduce voxelotor dose (see Dosage Modifications).

            Monitor Closely (260)

            • 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.

            • abiraterone

              isoniazid increases levels of abiraterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid or use with caution, strong inhibitors of 3A4 during abiraterone therapy.

            • 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.

            • alitretinoin

              isoniazid will increase the level or effect of alitretinoin by affecting hepatic/intestinal enzyme CYP3A4 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 enzyme CYP1A2 metabolism. Use Caution/Monitor.

              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.

            • 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).

            • clobetasone

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

            • clomipramine

              isoniazid will increase the level or effect of clomipramine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

              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 enzyme CYP1A2 metabolism. Use Caution/Monitor.

              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

              cocaine 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.

            • 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

              isoniazid will increase the level or effect of duloxetine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

              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.

            • eltrombopag

              isoniazid will increase the level or effect of eltrombopag by affecting hepatic enzyme CYP1A2 metabolism. 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.

            • frovatriptan

              isoniazid will increase the level or effect of frovatriptan by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

              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.

            • 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

              isoniazid will increase the level or effect of hydroxyprogesterone caproate 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 CYP1A2 metabolism. Use Caution/Monitor.

              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).

            • 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.

            • lidocaine

              isoniazid will increase the level or effect of lidocaine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

            • 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.

            • 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

            • 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.

            • mexiletine

              isoniazid will increase the level or effect of mexiletine by affecting hepatic enzyme CYP1A2 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.

            • nortriptyline

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

            • olanzapine

              isoniazid will increase the level or effect of olanzapine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

            • 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 enzyme CYP1A2 metabolism. Use Caution/Monitor. CYP-450 inhibitors may decrease clearance of ondansetron. However, no dosage adjustment for ondansetron is recommended

              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.

            • 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.

            • ramelteon

              isoniazid will increase the level or effect of ramelteon by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

            • rasagiline

              isoniazid will increase the level or effect of rasagiline by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor. Isoniazid shows only negligible inhibition of CYP1A2, caution is advised. Recommended dose of rasagiline is 0.5mg daily in combination with CYP1A2 inhibitors.

              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.

            • riluzole

              isoniazid will increase the level or effect of riluzole by affecting hepatic enzyme CYP1A2 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.

            • ropinirole

              isoniazid will increase the level or effect of ropinirole by affecting hepatic enzyme CYP1A2 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 enzyme CYP1A2 metabolism. Use Caution/Monitor.

              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.

            • 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.

            • vardenafil

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

            • 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 affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor.

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

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

            • zanubrutinib

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

            • 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 (79)

            • 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.

            • antipyrine

              isoniazid will increase the level or effect of antipyrine by affecting hepatic enzyme CYP1A2 metabolism. Minor/Significance Unknown.

            • asenapine

              isoniazid will increase the level or effect of asenapine by affecting hepatic enzyme CYP1A2 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.

            • caffeine

              isoniazid will increase the level or effect of caffeine by affecting hepatic enzyme CYP1A2 metabolism. 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.

            • desipramine

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

            • 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.

            • 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.

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            Adverse Effects

            >10%

            Mild incr LFTs (10-20%)

            Peripheral neuropathy (dose-related incidence, 10-20% incidence with 10 mg/kg/d)

            Loss of appetite

            Nausea

            Vomiting

            Stomach pain

            Weakness

            1-10%

            Dizziness

            Slurred speech

            Lethargy

            Progressive liver damage (increases with age; 2.3% in pts > 50 yo)

            Hyperreflexia

            <1%

            Agranulocytosis

            Anemia

            Megaloblastic anemia

            Thrombocytopenia

            Systemic lupus erythematosus

            Seizure

            • other adverse reactions reported: pancreatitis; toxic epidermal necrolysis, and drug reaction with eosinophilia syndrome(DRESS)
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            Warnings

            Black Box Warnings

            Severe and sometimes fatal hepatitis may occur within the first 3 months of treatment and many months after treatment. Risk is related to age and increased with daily alcohol consumption.

            Patients should be instructed about signs and symptoms of hepatitis.

            Contraindications

            Prev INH hepatic injury or reaction; acute liver dz; pancreatitis

            Hypersensitivity

            • Isoniazid is contraindicated in patients who develop severe hypersensitivity reactions, including drug-induced hepatitis; previous isoniazid-associated hepatic injury; severe adverse reactions to isoniazid such as drug fever, chills, arthritis; and acute liver disease of any etiology

            Cautions

            Alcohol or illicit injectable drug use, predisposition to neuropathy, malnourished, severe renal impairment, chronic liver dz

            Use w/ other anti-TB agents

            Give pyridoxine (B6) concurrently for pregnant women, malnourished pts. or those with neuropathic diathesis

            Alcohol use, renal or hepatic dysfunction will affect serum levels

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            Pregnancy & Lactation

            Pregnancy Category: C

            Lactation: distributed into milk but safe for nursing infants

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.

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            Pharmacology

            Mechanism of Action

            Unknown: prob. inhibits cell-wall biosynthesis by interfering with lipid and DNA synthesis (bactericidal)

            Absorption

            Rapid and complete; rate can be slowed with food Peak Plasma Time: 1-2 hr

            Distribution

            All body tissues and fluids including CSF; crosses placenta; enters breast milk

            Protein Bound: 10-15%

            Metabolism

            Hepatic with decay rate determined genetically by acetylation phenotype

            Elimination

            Half-life elimination: fast acetylators: 30-100 min; slow acetylators: 2-5 hr; may be prolonged with hepatic or severe renal impairment

            Excretion: Urine (75-95%); feces

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            Administration

            IM Preparation

            At low temperatures, isoniazid in solution tends to crystallize; warm injection to room temperature to redissolve crystals prior to use

            IM Administration

            May be given by IM injection when oral therapy is not possible

            Storage

            Protect from light

            Store at <40°C, preferably between 15-30°C

            Protect from freezing

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            Images

            BRAND FORM. UNIT PRICE PILL IMAGE
            isoniazid oral
            -
            300 mg tablet
            isoniazid oral
            -
            100 mg tablet
            isoniazid oral
            -
            300 mg tablet
            isoniazid oral
            -
            300 mg tablet
            isoniazid oral
            -
            300 mg tablet
            isoniazid oral
            -
            100 mg tablet
            isoniazid oral
            -
            50 mg/5 mL solution

            Copyright © 2010 First DataBank, Inc.

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            Patient Handout

            Select a drug:
            Patient Education
            isoniazid oral

            ISONIAZID - ORAL

            (EYE-soe-NYE-a-zid)

            COMMON BRAND NAME(S): Niazid

            WARNING: Isoniazid has rarely caused very serious (possibly fatal) liver disease. The risk of liver disease is increased in people who are 35 years and older, who use alcohol or illegal injection drugs, or who currently have long-term liver problems. Tell your doctor right away if you develop symptoms of liver disease, including persistent nausea/vomiting, severe stomach/abdominal pain, unusual weakness/tiredness, dark urine, yellowing eyes/skin.Your doctor should order liver function tests while you are taking this medication. Keep all medical and laboratory appointments.

            USES: Isoniazid is used with other medications to treat active tuberculosis (TB) infections. It is also used alone to prevent active TB infections in people who may be infected with the bacteria (people with positive TB skin test). Isoniazid is an antibiotic and works by stopping the growth of bacteria.This antibiotic treats only bacterial infections. It will not work for viral infections (such as common cold, flu). Using any antibiotic when it is not needed can cause it to not work for future infections.

            HOW TO USE: Take this medication by mouth on an empty stomach (1 hour before or 2 hours after meals) as directed by your doctor. If you are using the liquid form of this medication, carefully measure the dose using a special measuring device/spoon. Do not use a household spoon because you may not get the correct dose.If you also take antacids that contain aluminum, take this medication at least 1 hour before the antacid.Dosage is based on your age, weight, medical condition, and response to treatment.For the best effect, take this drug at evenly spaced times. If you are taking this medication daily, take it at the same time each day. If you are taking this medication on a weekly schedule, take it on the same day(s) of the week and at the same time each day. Mark the days on the calendar when you need to take the medication.Continue to take this medication (and other TB medications) until the full prescribed amount is finished, even if symptoms disappear. Stopping the medication too early or skipping doses may allow the bacteria to continue to grow, which may result in a return of the infection and cause the infection to be more difficult to treat (resistant).Your doctor may also direct you to take vitamin B6 (pyridoxine) to help prevent certain side effects (such as nerve problems) from isoniazid. Follow your doctor's instructions carefully.Isoniazid may interact with foods containing tyramine/histamine (such as cheese, red wine, certain types of fish). This interaction may cause increased blood pressure, flushing of the skin, headache, dizziness, or fast/pounding heartbeat. Tell your doctor right away if any of these symptoms occur. Your doctor may recommend that you follow a special diet while taking this medication. Consult your doctor for more details.Tell your doctor if your condition persists or worsens.

            SIDE EFFECTS: See also Warning section.Nausea/vomiting or stomach upset may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor right away if any of these unlikely but serious side effects occur: numbness/tingling of arms/legs, painful/swollen joints.Tell your doctor right away if any of these rare but serious side effects occur: increased thirst/urination, vision changes, easy bruising/bleeding, mental/mood changes (such as confusion, psychosis), seizures.A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: fever that doesn't go away, new or worsening lymph node swelling, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

            PRECAUTIONS: See also Warning section.Before taking isoniazid, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: previous severe reaction from isoniazid (such as liver disease), liver disease, alcohol use, HIV infection, kidney disease, diabetes, numbness/tingling of arms/legs (peripheral neuropathy), recent childbirth.Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).Alcohol may increase the risk of liver disease. Avoid alcoholic beverages while using this medication.This product may cause live bacterial vaccines (such as BCG vaccine) to not work as well. Do not have any immunizations/vaccinations while using this medication unless your doctor tells you to.Liquid forms of this medication may contain sugar. Caution is advised if you have diabetes or any other condition that requires you to limit/avoid sugar. Ask your doctor or pharmacist about using this product safely.During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.This product passes into breast milk but is unlikely to harm a nursing infant. Consult your doctor before breast-feeding.

            DRUG INTERACTIONS: See also How to Use section.Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.Some products that may interact with this drug include: acetaminophen, certain azole antifungals (itraconazole, ketoconazole), disulfiram, MAO inhibitors (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine), phenytoin, SSRI antidepressants (such as fluoxetine, sertraline), valproic acid.This medication may interfere with certain laboratory tests (including urine glucose tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

            OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: vision changes, slow/shallow breathing, severe drowsiness.

            NOTES: Do not share this medication with others.Laboratory and/or medical tests (such as sputum test, kidney/liver function, complete blood count) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

            MISSED DOSE: It is important to take each dose of this medication as scheduled. If you are taking this medication daily and miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.If you are taking this drug on a weekly schedule and miss a dose, take it as soon as you remember if it is on the same day. If you remember on the next day or later, ask your doctor or pharmacist right away for a new dosing schedule. Do not double the dose to catch up.

            STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

            Information last revised August 2021. Copyright(c) 2021 First Databank, Inc.

            IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

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            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

            Adding plans allows you to:

            • View the formulary and any restrictions for each plan.
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            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.