Phentermine and topiramate and Valproic acid interaction
Phentermine and topiramate and Valproic acid: 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 Valproic acid label · effective 2024-05-02
Children under the age of two years are at a considerably increased risk of developing fatal hepatotoxicity, especially those on multiple anticonvulsants, those with congenital metabolic disorders, those with severe seizure disorders accompanied by mental retardation, and those with organic brain disease.
In patients over two years of age who are clinically suspected of having a hereditary mitochondrial disease, valproic acid oral solution should only be used after other anticonvulsants have failed.
Hyperammonemia and hyperammonemic encephalopathy; measure ammonia level if unexplained lethargy and vomiting or changes in mental status, and also with concomitant topiramate use; consider discontinuation of valproate therapy (5.6, 5.9, 5.10)
This adverse reaction can also occur in patients using concomitant topiramate with valproate after starting topiramate treatment or after increasing the daily dose of topiramate [see Drug Interactions (7.3) ].
Topiramate Concomitant administration of valproate and topiramate has been associated with hyperammonemia with and without encephalopathy [see Contraindications (4) and Warnings and Precautions (5.6, 5.9, 5.10 ) ].
From the Phentermine and topiramate label · effective 2026-05-18
Concomitant administration of valproic acid and topiramate has been associated with hyperammonemia with and without encephalopathy.
Concomitant administration of topiramate with valproic acid in patients has also been associated with hypothermia (with and without hyperammonemia).
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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.