A 53-yr-old man sequentially developed aplastic anemia from phenytoin and carbamazepine. Both compounds undergo metabolism to potentially toxic arene oxide intermediates. We tested the hypothesis that the patient's adverse reactions were due to a defect in detoxification of such metabolites by challenging his peripheral lymphocytes with drug metabolites generated by a murine hepatic microsomal system in vitro. The patient's cell viability was normal in the absence of drugs. However, his cells showed greater toxicity from both phenytoin and carbamazepine metabolites than did controls. Toxicity was dependent on microsomes and NADPH. Intermediate toxicity was noted in cells from the patient's mother. The results provide the first evidence for a role of arene oxide drug metabolites in aplastic anemia in humans and suggest that enhanced susceptibility to toxicity may be based on an inherited abnormality in metabolite detoxification.
A young woman with hypertrophic cardiomyopathy confirmed by echocardiography and cardiac catheterization presented with chest pain and features of a large left ventricular aneurysm. The initial diagnosis was myocardial ischemia with either an evolving or an ancient myocardial infarction. Subsequently, verapamil therapy was associated with complete resolution of the extensive left ventricular wall motion abnormalities, normalization of left ventricular ejection fraction and a minimal myocardial infarction. Normal thallium uptake on single photon emission computed tomographic scintigraphy early in the hospital course predicted myocardial viability in the region of the aneurysm. Thus, orally administered verapamil may reverse spontaneous extensive myocardial ischemia in hypertrophic cardiomyopathy and possibly limit the extent of myocardial infarction in such circumstances.
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