Abstract
Idiosyncratic “hypersensitivity” reactions to sulphonamides may be mediated by reactive intermediates. The diagnosis of these reactions is often difficult; moreover, the pathogenesis ot these reactions has been extremely difficult to understand and study. We have demonstrated the cytochrome P-450 dependent production of hydroxylamine metabolites of the sulphonamides by murine microsomal preparations. In order to pursue the role of such a metabolite in mediating sulphonamide toxicity, we set out to synthesize and characterize the hydroxylamine (HA)derviative of sulfamethoxazole (SMX). Synthesis of the HA was initiated by mixing 4-nitrobenzene sulfonlyl chloride and 3-amino-5-methylisoxazole in pyridine. Nitro-sulfamethoxazole was recrystallised and dissolved in ethanol and reduced under hydrogen in the presence of a poisoned catalyst. The HA was recrystallized using a mixture of ethyl acetate and toluene. Analysis by TLC and HPLC demonstrated that the product was 95% pure. The HA was then used in a lymphocyte assay using cells from a normal volunteer. Toxicity was assessed by using MTT (tetrazolium) as a marker in an automated microtitre plate assay. Over a range of 0.1 to 10 mM, the HA produced concentration-dependent toxicity (39% deal cells at 10mM/ml). SMX was non-toxic even at 10 mM. In the presence of murine hepatic microsomes, SMX produces toxicity. At 750 mM, cell death is comparable to 2.5 mM HA, suggesting a 0.3% conversion to the metabolite by microsomes. Chemically-synthesized reactive intermediates such as this compound are useful in studying the pathogenesis of poorly-understood adverse reactions such as idiosyncratic reactions attributed to the sulphonamides; additionally, these compounds may be very useful in the development of diagnostic tests that will quickly, accurately and safely diagnose these adverse reactions.
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Rieder, M., Uetrecht, J. & Soielbera, S. CHEMICAL SYNTHESIS AND IN VITRO TOXICITY OF A REACTIVE INTERMEDIATE OF SULFAMETHOXAZOLE. Pediatr Res 21 (Suppl 4), 241 (1987). https://doi.org/10.1203/00006450-198704010-00443
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DOI: https://doi.org/10.1203/00006450-198704010-00443