SULFA DRUG

in full sulfonamide drug, sulfa also spelled sulpha, any member of a group of synthetic antibacterial drugs containing the sulfanilamide molecular structure, and including sulfanilamide, sulfadiazine, sulfapyridine, sulfathiazole, and other substances. The antibacterial effects of sulfonamides were first observed in 1932, when Gerhard Domagk, a German bacteriologist and pathologist, noted the effects of Prontosil (q.v.; a red dye) on streptococcal infections in mice. French investigators were first to prove that sulfonamide was the active principle in the dye. American researchers later helped create a rational basis for sulfonamide chemotherapy. Sulfonamides were the first chemical substances that were systematically used to cure and prevent bacterial infections in humans. They are bacteriostatic drugs; i.e., they inhibit the growth and multiplication of bacteria but do not kill them. They act by interfering with enzyme systems essential to normal metabolic and growth patterns of bacteria. Although more than 5,000 sulfa drugs have been prepared and tested, fewer than 20 continue to have therapeutic value because resistant strains of bacteria have developed. Sulfa drugs are assigned to four groups based on the rapidity with which they are absorbed and excreted. The most common side effects of sulfa drugs include nausea, vomiting, and mental confusion. Other side effects include fever, skin eruptions, anemia, leukopenia, and irritation of the liver or kidneys. More potent antibacterial drugs have largely replaced the sulfa drugs. They are still used, however, in the treatment of urinary tract infection.