Drug interactions
Carbamazepine + Isoniazid
Severity: Major
Carbamazepine and Isoniazid: major 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 raises carbamazepine concentrations, leading to toxicity such as dizziness, ataxia, diplopia and nausea, and both drugs are hepatotoxic. Carbamazepine may in turn increase the formation of toxic isoniazid metabolites.
What this interaction means in plain words
Carbamazepine and Isoniazid can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Carbamazepine belongs to Central Nervous System; Isoniazid belongs to Anti Bacterial.
Why it happens
Isoniazid inhibits CYP3A4 metabolism of carbamazepine, and carbamazepine induction may increase hepatotoxic isoniazid metabolites.
What to do
Monitor carbamazepine levels and reduce the dose if needed. Check liver function regularly and watch for signs of hepatotoxicity.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Isoniazid
Other interactions of Carbamazepine
- Artemether / lumefantrine + Carbamazepine Contraindicated
- Cabotegravir + Carbamazepine Contraindicated
- Carbamazepine + Delamanid Contraindicated
- Carbamazepine + Dienogest / estradiol valerate Contraindicated
- Carbamazepine + Doravirine Contraindicated
- Carbamazepine + Elbasvir / grazoprevir Contraindicated
Frequently asked questions
Can I take Carbamazepine with Isoniazid?
MediHelp rates the interaction as major. Carbamazepine and Isoniazid can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Isoniazid raises carbamazepine concentrations, leading to toxicity such as dizziness, ataxia, diplopia and nausea, and both drugs are hepatotoxic. Carbamazepine may in turn increase the formation of toxic isoniazid metabolites.
How serious is the interaction between Carbamazepine and Isoniazid?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor carbamazepine levels and reduce the dose if needed. Check liver function regularly and watch for signs of hepatotoxicity.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Didanosine. The full list is on the Isoniazid page.
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