- Covalent binding of the nitroso metabolite of sulfamethoxazole leads to toxicity and major histocompatibility complex-restricted antigen presentation. Naisbitt, D.J., Farrell, J., Gordon, S.F., Maggs, J.L., Burkhart, C., Pichler, W.J., Pirmohamed, M., Park, B.K. Mol. Pharmacol. (2002)