Sulfametoxydiazine (INN) or sulfamethoxydiazine (USAN: sulfameter) is a long-acting sulfonamide antibacterial. It is used as a leprostatic agent and in the treatment of urinary tract infections. Sulfametoxydiazine (INN) or sulfamethoxydiazine (USAN: sulfameter) is a long-acting sulfonamide antibacterial. It is used as a leprostatic agent and in the treatment of urinary tract infections.