Trimethoprim/sulfamethoxazole (TMP/SMX), also known as co-trimoxazole among other names, is an antibiotic used to treat a variety of bacterial infections. It consists of one part trimethoprim to five parts sulfamethoxazole. It is used for urinary tract infections, MRSA skin infections, travelers' diarrhea, respiratory tract infections, and cholera, among others. It may be used both to treat and prevent pneumocystis pneumonia in people with HIV/AIDS. It can be given by mouth or intravenously.