Definition of Sulfa drug

موضوع: Definition of Sulfa drug الجمعة 28 نوفمبر 2008, 2:48 am

Sulfa drug: One of the sulfonamides, the sulfa-related antibiotics which are used to treat bacterial and some fungal infections.

The first sulfa drug was prontosil. It was discovered by the German physician and chemist Gerhard Domagk in 1935. The sulfa family of drugs includes sulfadiazine, sulfamethizole (brand name: Thiosulfil Forte), sulfamethoxazole (Gantanol), sulfasalazine (Azulfidine), sulfisoxazole (Gantrisin), and various high-strength combinations of three sulfonamides.

Sulfa drugs kill bacteria and fungi by interfering with their metabolism. They were the "wonder drugs" before penicillin and are still used today. Because sulfa drugs concentrate in the urine before being excreted, treating urinary tract infections is one of their most common uses. Sulfa drugs can have a number of interactions with prescription and over-the-counter drugs (including PABA sunscreens), and are not appropriate for people with some health conditions.

Antibacterial Agents - Sulfa Drugs

Sulfonamides or Sulfa Drugs as Antimetabolites:

The sulfonamides are synthetic antimicrobial agents with a wide spectrum encompassing most gram-positive and many gram-negative organisms. These drugs were the first efficient treatment to be employed systematically for the prevention and cure of bacterial infections.

Their use introduced and substantiated the concept of metabolic antagonism. Sulfonamides, as antimetabolites, compete with para-aminobenzoic acid (PABA) for incorporation into folic acid. The action of sulfonamides illustrates the principle of selective toxicity where some difference between mammal cells and bacterial cells is exploited. All cells require folic acid for growth. Folic acid (as a vitamin is in food) diffuses or is transported into human cells. However, folic acid cannot cross bacterial cell walls by diffusion or active transport. For this reason bacteria must synthesize folic acid from p-aminobenzoic acid.

Sulfonamides or sulfa drugs have the following general structures as shown in the graphic

Sulfanilamide which was the first compound used of this type has H's at R1 and R4. To date about 15,000 sulfonamide derivatives, analogues, and related compounds have been synthesized.

This has lead to the discovery of many useful drugs which are effective for diuretics, antimalerial and leprosy agents, and antithyroid agents. The basic structure of sulfonamide cannot be modified if it is to be an effective competitive "mimic" for p-aminobenzoic acid. Essential structural features are the benzene ring with two substituents para to each other; an amino group in the fourth position; and the singly substituted 1-sulfonamido group.

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