Differences in metabolism of sulfonamides predisposing to idiosyncratic toxicity.
Individual differences in metabolism of the sulfonamides may predispose patients to idiosyncratic reactions. Sulfonamides are metabolized by N-acetylation (mediated by a genetically polymorphic enzyme) and oxidation to potentially toxic metabolites. We examined 6 patients who had severe reactions to sulfonamides and compared them with 20 controls. Acetylator phenotype was determined with caffeine, a safe in-vivo probe of enzyme activity. All 6 patients were slow acetylators (expected, 55%; p less than 0.05). Detoxification of oxidative metabolites was studied in vitro with a lymphocyte assay evaluating cell death from metabolites generated by a murine hepatic microsomal system. Cells from each patient showed increased toxicity from sulfonamide metabolites but not from the drugs themselves. Cells from parents of 3 patients had intermediate toxicity from sulfonamide metabolites, whereas cells from a sibling of 1 patient had a normal response. Susceptibility to sulfonamide reactions may be due to interaction of metabolic pathways, possibly under genetic control, regulating N-acetylation and specific detoxification of toxic metabolites of the drugs.[1]References
- Differences in metabolism of sulfonamides predisposing to idiosyncratic toxicity. Shear, N.H., Spielberg, S.P., Grant, D.M., Tang, B.K., Kalow, W. Ann. Intern. Med. (1986) [Pubmed]
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