Sulfamethoxazole, usually combined with trimethoprim, is an antibiotic used to treat a variety of bacterial infections. Its common uses include:

• Urinary tract infections
• Middle ear infections (otitis media)
• Bronchitis and acute exacerbations of chronic bronchitis
• Traveler's diarrhea
• Shigellosis (bacillary dysentery)
• Pneumocystis jiroveci pneumonia (PCP), especially in people with weakened immune systems such as those with HIV/AIDS, cancer, or transplant patients
• Prostatitis
• Some gastrointestinal infections caused by bacteria

The combination works by inhibiting bacterial folic acid synthesis, which is essential for bacterial growth and replication, making it bacteriostatic