COLIPRIM injection is a sterile solution formulated as soluble injectable preparation composed of trimethoprim and Sulphadiazine. The action of the combination proved to be bactericidal, whereas the components separately were only bacteriostatic in action. Sulphonamides act as an analogue for para-aminobenzoic acid, (PABA) which itself a part of the vitamin, folic acid. In organisms that synthesis their own folic acid, sulphonamides as sulphadiazine acts by blocking the synthesis of folic acid. Sulphonamides are active against bacteria but not against higher organisms as bacteria synthetic their own folic acid whereas higher animals or higher organisms obtained folic acid from the diet