Isoniazid and Phentermine and topiramate interaction
Isoniazid and Phentermine and topiramate: 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 Isoniazid label · effective 2026-04-27
To avoid phenytoin intoxication, appropriate adjustment of the anticonvulsant should be made 5,6 .
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 .
From the Phentermine and topiramate label · effective 2026-05-18
…Warnings and Precautions (5.1) and Use in Specific Populations (8.1) ] With glaucoma [see Warnings and Precautions (5.3) ] With hyperthyroidism Taking or within 14 days of stopping a monoamine oxidase inhibitors [see Drug Interactions (7) ] With known hypersensitivity to phentermine, topiramate or any of the excipients in phentermine and topiramate extended-release…
Taking or within 14 days of stopping monoamine oxidase inhibitors ( 4 )
Intervention Concomitant use of phentermine and topiramate extended-release capsules are contraindicated during MAOI treatment and within 14 days of stopping an MAOI.
Clinically Significant Drug Interactions with Phentermine and Topiramate Extended-Release Capsules Monoamine Oxidase Inhibitors Clinical Impact Concomitant use of phentermine with monoamine oxidase inhibitors (MAOIs) increases the risk of hypertensive crisis.
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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.