(Generic) Sulfamethoxazole and trimethoprim is an antibiotic used to treat a wide range of infections in horses, dogs, cats and other species of animals. Each 5 ml (1 tsp) SMZ/TMP Oral Suspension contains 200 mg sulfamethoxazole and 40 mg trimethoprim. SMZ/TMP Oral Suspension may be used to treat bacterial and protozoal infections. SMZ/TMP may be used in horses where control of bacterial infections is required during treatment of acute strangles, respiratory tract infections, acute urogenital infections, wound infections and abscesses. Sulfamethoxazole and trimethoprim.