Title: Sulfa drug | medicine | Britannica
Headings: Sulfa drug
Sulfa drug
medicine
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Content: Trisulfapyrimidine (triple sulfa), a combination of sulfadiazine, sulfamerazine, and sulfamethazine, is used in the treatment of vaginal infections, and several sulfa drugs are used in combination with antibiotics to treat a wide range of conditions, from skin burns to malaria to pneumonia in HIV/ AIDS patients. Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now
Sulfa drugs are bacteriostatic; i.e., they inhibit the growth and multiplication of bacteria but do not kill them. They act by interfering with the synthesis of folic acid (folate), a member of the vitamin B complex present in all living cells. Most bacteria make their own folic acid from simpler starting materials; humans and other higher animals, however, must obtain folic acid in the diet. Thus, sulfa drugs can inhibit the growth of invading microorganisms without harming the host. When trimethoprim (a dihydrofolate reductase inhibitor) is given with sulfamethoxazole, the sequential blockage of the pathway produced by the two drugs achieves markedly greater inhibition of folic acid synthesis. As a result, this combination is valuable in treating urinary tract infections and some systemic infections.