Isoniazid

Name: Isoniazid Drug Interactions
Creator: Dr. Brian Staiger, PharmD, BCPS

25 interactions 1 explained in plain English

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated Jul 4, 2026 · Editorial policy · Data sources

Sources: FDA prescribing information (Structured Product Labeling), the published literature cited in each entry, DDInter 2.0 (a major open-access drug-interaction database), and legacy DrugBank interaction data distributed by the NIH's RxNav service (decommissioned in 2024) — analyzed and reviewed by our pharmacist team. How we build this library →

Most serious with: Glimepiride Nifedipine Mercaptopurine Loperamide Azathioprine Methotrexate Injection

18 Major 7 Moderate

All (25) Major (18) Moderate (7)

Moderate

Isoniazid Clopidogrel Plavix Reduced clopidogrel active metabolite exposure and reduced platelet inhibition Details Isoniazid Disulfiram Antabuse Increased risk of disulfiram CNS effects (changes in behavior, coordination, and mood) Details Isoniazid Dofetilide Tikosyn Increased dofetilide exposure Details Isoniazid Folic Acid Folacin Reduced folic acid exposure and reduced efficacy of folic acid Details Isoniazid Hydrocortisone Ala-Cort Increased hydrocortisone exposure and an increased risk of hydrocortisone-related adverse reactions Details Isoniazid Hydrocortisone Injection A-Hydrocort® Increased hydrocortisone exposure and an increased risk of hydrocortisone-related adverse reactions Details Isoniazid Metformin Fortamet® An increased risk of hyperglycemia and potential loss of glycemic control Details

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Educational information only, not medical advice. Always confirm interactions with your pharmacist or prescriber before making any change to your medications.