Drug interactions
Isoniazid + Niacin
Severity: Minor
Isoniazid and Niacin: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Isoniazid can interfere with niacin (nicotinamide) status because it disrupts pyridoxine-dependent conversion of tryptophan to niacin, and pellagra-like syndromes have been reported with isoniazid. Supplemental niacin used therapeutically is unlikely to be blunted in a clinically important way.
What this interaction means in plain words
Isoniazid and Niacin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Isoniazid belongs to Anti Bacterial; Niacin belongs to Cardiovascular.
Why it happens
Isoniazid impairs pyridoxine-dependent niacin synthesis and may interfere with nicotinamide metabolism.
What to do
No dose change is typically needed; ensure pyridoxine supplementation with isoniazid and watch for pellagra signs in malnourished patients.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Isoniazid
Other interactions of Niacin
- Alogliptin-metformin + Niacin Moderate
- Atorvastatin + Niacin Moderate
- Canagliflozin-metformin + Niacin Moderate
- Cholestyramine + Niacin Moderate
- Colestipol + Niacin Moderate
- Dapagliflozin-metformin + Niacin Moderate
Frequently asked questions
Can I take Isoniazid with Niacin?
MediHelp rates the interaction as minor. Isoniazid and Niacin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Isoniazid can interfere with niacin (nicotinamide) status because it disrupts pyridoxine-dependent conversion of tryptophan to niacin, and pellagra-like syndromes have been reported with isoniazid. Supplemental niacin used therapeutically is unlikely to be blunted in a clinically important way.
How serious is the interaction between Isoniazid and Niacin?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No dose change is typically needed; ensure pyridoxine supplementation with isoniazid and watch for pellagra signs in malnourished patients.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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