Sulfamethoxazole/trimethoprim is a prescription medication used to treat bacterial infections of the urinary tract, lungs, intestines, and ears. It also treats infections that cause traveler’s diarrhea. This medication is a single formulation containing 2 drugs, sulfamethoxazole and trimethoprim. Sulfamethoxazole/trimethoprim both belong to a group of drugs called antibiotics. These work by stopping bacterial growth.

Sulfamethoxazole/trimethoprim comes in tablet and oral (by mouth) suspension forms and is taken up to 4 times a day, with or without food.

Common side effects of sulfamethoxazole/trimethoprim include diarrhea, vomiting, anorexia, and skin reactions like hives or itching.