Drug Interactions Aspirin - See WARNINGS Acetazolamide modifies phenytoin metabolism with increased serum levels of phenytoin. By decreasing the gastrointestinal absorption of primidone, acetazolamide may decrease serum concentrations of primidone and its metabolites, with a consequent possible decrease in anticonvulsant effect. Caution is advised when beginning, discontinuing, or changing the dose of acetazolamide in patients receiving primidone.
Source: FDA drug label - acetazolamide extended-release