Sulfasalazine. Pharmacology, clinical use, toxicity, and related new drug development.

Sulfasalazine is metabolized by intestinal bacteria, resulting in the release of sulfapyridine and 5-aminosalicylate. The drug is useful in the treatment of active ulcerative colitis as well as in preventing relapses of the disease in remission. Although effective in active Crohn's disease as well, sulfasalazine appears to be of greater benefit to patients with colitis and ileocolitis than those with ileitis alone. 5-Aminosalicylate itself is efficacious when given in enema and suppository form; oral agents capable of delivering 5-aminosalicylate to distal disease sites are now under study. The drug's mechanism of action may relate to its effects on prostaglandin synthesis or interference with arachidonic acid metabolism by the lipoxygenase pathway. Common adverse reactions of sulfasalazine, including nausea, headache, and anorexia, as well as hemolysis, are associated with high serum sulfapyridine levels and often can be avoided by lowering the dose of sulfasalazine. Mild allergic reactions, such as rash and fever, may be overcome by gradual desensitization.