Isoniazid Drug Interactions

Antibiotic interactions vary significantly by class. Key interactions affect anticoagulation, other drug metabolism, and absorption.

Key Drug Interactions

→Warfarin: many antibiotics enhance anticoagulant effect — monitor INR
→Oral contraceptives: some antibiotics may reduce efficacy (mainly rifampicin)
→Antacids / iron / dairy (quinolones, tetracyclines): reduced absorption
→Class-specific interactions vary widely

Alcohol Interactions

→Avoid alcohol with metronidazole and tinidazole (causes severe reaction). Some other antibiotics can cause GI upset when combined with alcohol. Check specific guidance.

Supplement and Food Interactions

→Probiotics may help reduce antibiotic-associated diarrhoea. Iron and calcium supplements can reduce absorption of quinolones and tetracyclines.

Safety Note

Always tell your doctor and pharmacist about all prescription medicines, non-prescription medicines, vitamins, and herbal or dietary supplements before starting Isoniazid. Keep an up-to-date medicines list to share with all healthcare providers.

Frequently Asked Questions

Can I take Isoniazid with common over-the-counter medicines?

Some OTC medications interact with Isoniazid. NSAIDs, aspirin, antihistamines, antacids, and herbal products can all have interactions. Ask your pharmacist to check for interactions before taking any new OTC product.

Can I drink alcohol while taking Isoniazid?

Avoid alcohol with metronidazole and tinidazole (causes severe reaction). Some other antibiotics can cause GI upset when combined with alcohol. Check specific guidance.

More About Isoniazid

Dosage & Administration

Side Effects

Warnings & Precautions

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Medical Disclaimer: This drug reference is provided for informational purposes only and is not a substitute for professional medical advice. Always consult your physician or pharmacist before changing your medication. Information reviewed by the vHospital Editorial Team · Sources: WHO, BNF, FDA prescribing information.