| Item |
Information |
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Drug Groups
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approved |
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Description
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A bacteriostatic antibacterial agent that interferes with folic acid synthesis in susceptible bacteria. Its broad spectrum of activity has been limited by the development of resistance. (From Martindale, The Extra Pharmacopoeia, 30th ed, p208) |
| Indication |
For the treatment bacterial infections causing bronchitis, prostatitis and urinary tract infections. |
| Pharmacology |
Sulfamethoxazole is a sulfonamide drug that inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid (PABA) for binding to dihydropteroate synthetase (dihydrofolate synthetase). Sulfamethoxazole is bacteriostatic in nature. Inhibition of dihydrofolic acid synthesis decreases the synthesis of bacterial nucleotides and DNA. Sulfamethoxazole is normally given in combination with Trimethoprim, a dihydrofolate reductase inhibitor, which inhibits the reduction of dihydrofolic acid to tetrahydrofolic acid. Studies have shown that bacterial resistance develops more slowly with the combination of the two drugs than with either Trimethoprim or Sulfamethoxazole alone. |
| Toxicity |
Sulfamethoxazole may cause nausea, vomiting, diarrhea and hypersensitivity reactions. Hematologic effects such as anemia, agranulocytosis, thrombocytopenia and hemolytic anemia in patients with glucose-6-phosphate dehydrogenase deficiency may also occur. Sulfamethoxazole may displace bilirubin from albumin binding sites causing jaundice or kernicterus in newborns. |
| Affected Organisms |
| • |
Gram negative and gram positive bacteria |
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| Biotransformation |
Hepatic. The metabolism of sulfamethoxazole occurs predominately by N4-acetylation, although the glucuronide conjugate has been identified. |
| Absorption |
Rapidly absorbed following oral administration. Also well-absorbed topically. |
| Half Life |
10 hours |
| Protein Binding |
70% |
| External Links |
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