Bactrim (sulfamethoxazole / trimethoprim) is a sulfa antibiotic that treats bacterial infections. The most common Bactrim side effects are nausea, diarrhea, and skin changes. Medscape - Indication-specific dosing for Bactrim, Bactrim DS, Septra, Septra DS, Cotrim, cotrimoxazole, Sulfatrim (trimethoprim, sulfamethoxazole), frequency-based adverse effects. Sulfamethoxazole and trimethoprim is a combination antibiotic used to treat ear infections, urinary tract infections, bronchitis, traveler's diarrhea, shigellosis, and Pneumocystis jiroveci pneumonia. Sulfamethoxazole and trimethoprim may also be used for purposes not listed in this medication guide. Treatment options Trimethoprim-sulfamethoxazole (TMP-SMX) (sold as Bactrim,* Septra,* or Cotrim*) is the treatment of choice for cyclosporiasis. Sulfamethoxazole and trimethoprim combination is used to treat infections including urinary tract infections, middle ear infections (otitis media), bronchitis, traveler's diarrhea, and shigellosis (bacillary dysentery). Trimethoprim/sulfamethoxazole, sold under the trade names Bactrim, Cotrim (a short form of the British Approved Name, Co-trimoxazole) and Septra, among others, is a fixed-dose combination antibiotic medication used to treat a variety of bacterial infections. [2] Bactrim (Trimethoprim and Sulfamethoxazole) may treat UTI, side effects, dosage, drug interactions, warnings, patient labeling, and more Find patient medical information for Sulfamethoxazole/Trimethoprim (Bactrim, Septra, others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user. Learn about uses, side effects, dosage, and more for Bactrim. It's a prescription oral tablet used to treat certain types of infection in adults and some children. Bactrim and Bactrim DS are antibiotics used to treat ear infections, urinary tract infections, bronchitis, traveler's diarrhea, shigellosis, and Pneumocystis jiroveci pneumonia.