We read with interest the extensive review of drug interactions with warfarin by Holbrook et al.1 We strongly believe that sulfamethoxazole should be listed in the table stratifying warfarin drug interaction as a highly probable clinically significant interaction.
We recognize that in their comments, “azoles,” which include sulfamethoxazole, were mentioned as a class of medications inhibiting CYP1A2 or CYP3A4. There was no further discussion of this potentially dangerous drug interaction.
Campbell JE, Carter WH. Comments on the Important Drug Interaction of Warfarin and Sulfamethoxazole. Arch Intern Med. 2005;165(21):2540. doi:10.1001/archinte.165.21.2540-a