Drug interactions
Amitriptyline + Isoniazid
Severity: Moderate
Amitriptyline and Isoniazid: moderate 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 may increase amitriptyline concentrations by inhibiting CYP2C19 and other pathways, increasing anticholinergic and cardiac adverse effects. Isoniazid's weak MAO inhibition may also add serotonergic effects, though serious toxicity is uncommon.
What this interaction means in plain words
Amitriptyline and Isoniazid can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Amitriptyline belongs to Central Nervous System; Isoniazid belongs to Anti Bacterial.
Why it happens
Inhibition of CYP2C19/CYP3A4 metabolism of amitriptyline and weak MAO inhibition by isoniazid.
What to do
Start with a low amitriptyline dose and titrate to response, monitoring for anticholinergic effects, sedation and arrhythmia. Consider checking drug levels and ECG if symptoms occur.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Isoniazid
Other interactions of Amitriptyline
- Amitriptyline + Isocarboxazid Contraindicated
- Amitriptyline + Methylene blue Contraindicated
- Amitriptyline + Phenelzine Contraindicated
- Amitriptyline + Pimozide Contraindicated
- Amitriptyline + Procarbazine Contraindicated
- Amitriptyline + Safinamide Contraindicated
Frequently asked questions
Can I take Amitriptyline with Isoniazid?
MediHelp rates the interaction as moderate. Amitriptyline and Isoniazid can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Isoniazid may increase amitriptyline concentrations by inhibiting CYP2C19 and other pathways, increasing anticholinergic and cardiac adverse effects. Isoniazid's weak MAO inhibition may also add serotonergic effects, though serious toxicity is uncommon.
How serious is the interaction between Amitriptyline and Isoniazid?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Start with a low amitriptyline dose and titrate to response, monitoring for anticholinergic effects, sedation and arrhythmia. Consider checking drug levels and ECG if symptoms occur.
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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