Carbamazepine and Isoniazid interaction
Carbamazepine and Isoniazid: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Carbamazepine (EQUETRO) label · effective 2025-08-19
Concomitant use of monoamine oxidase inhibitors (MAOIs).
Before beginning treatment with EQUETRO, MAOIs should be discontinued for a minimum of 14 days.
Concomitant use with monoamine oxidase inhibitors (MAOIs) or use within 14 days of discontinuing an MAOI ( 4 )
Pharmacodynamic Drug Interactions M onoamine O xidase I nhibitors Concomitant treatment with EQUETRO is contraindicated during use of an MAOI or within 14 days after discontinuing an MAOI.
Isoniazid Concomitant use of carbamazepine and isoniazid has been reported to increase isoniazid-induced hepatotoxicity.
From the Isoniazid label · effective 2026-04-27
To avoid phenytoin intoxication, appropriate adjustment of the anticonvulsant should be made 5,6 .
Carbamazepine Isoniazid is known to slow the metabolism of carbamazepine and increase its serum levels.
Carbamazepine levels should be determined prior to concurrent administration with isoniazid, signs and symptoms of carbamazepine toxicity should be monitored closely, and appropriate dosage adjustment of the anticonvulsant should be made 3 .
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.