Co-trimoxazole (abbreviated SXT, TMP-SMX, TMP-SMZ or TMP- sulfa) is a sulfonamide antibiotic combination of trimethoprim and sulfamethoxazole, in the ratio of 1 to 5, used in the treatment of a variety of bacterial infections. The name co-trimoxazole is the British Approved Name, and has been marketed worldwide under many trade names including Septra (GSK), Bactrim (Roche), and various generic preparations. Sources differ as to whether co- trimoxazole usually is bactericidal or bacteriostatic.