Sulfanilamide is a sulfonamide antibacterial. Chemically, it is an organic compound consisting of an aniline derivatized with a sulfonamide group. Powdered sulfanilamide was used by the Allies in World War II to reduce infection rates and contributed to a dramatic reduction in mortality rates compared to previous wars. Modern antibiotics have supplanted sulfanilamide on the battlefield; however, sulfanilamide remains in use for treatment of vaginal yeast infections. As a sulfonamide antibiotic, sulfanilamide functions by competitively inhibiting enzymatic reactions involving para-aminobenzoic acid (PABA). PABA is needed in enzymatic reactions that produce folic acid, which acts as a coenzyme in the synthesis of purines and pyrimidines. Mammals do not synthesize their own folic acid so are unaffected by PABA inhibitors, which selectively kill bacteria.
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