Trimethoprim/sulphamethoxazole+glibenclamide Interactions

Two patients stabilised on glibenclamide for their diabetes became hypoglycaemic when they commenced trimethoprim/sulphamethoxazole for a bacterial infection. One patient had previously taken trimethoprim with glibenclamide without adverse effect. This interaction occurs because sulphonamides inhibit the hepatic metabolism of sulphonylureas by CYP2C9. In addition, high dose sulphonamides alone may, rarely, have a hypoglycaemic effect.

Reference

1. Juurlink DN, Mamdani M, Kopp A, Laupacis A, Redelmeier DA. Drug-drug interactions among elderly patients hospitalized for drug toxicity. JAMA 2003;289:1652-58.