Sulfonamides were the initial modern era antimicrobials and were first used in the treatment of humans in the early 1930's. SuThe sulfonamides are structural analogs of para-aminobenzoic acid (PABA), a compound required for growth and reproduction among many bacteria. These sulfur containing compounds act as competitive inhibitors of PABA giving them a bacteriostatic property.
Some antibiotics use a sulfonamide in combination with trimethoprim (TMP). TMP selectively inhibits the dihydrofolate reductases of bacterial cells but not human cells. DHT reductase is important in the generation of tetrahydrofolate, a derivative of folic acid which is essential for bacterial cell growth. Thus, the combination of sulfa and TMP produces a highly effective antibiotic. Click here for more information on Sulfamethoxazole- TMP, Sulfisoxazole-Erythromycin and Trimethoprim.