Summary
Because of the large interethnic differences in the incidence of poor metabolizer phenotypes, French Caucasians have been studied for two independant polymorphisms, debrisoquine/dextromethorphan and mephenytoin metabolism. One hundred and thirty-two unrelated French Caucasians were phenotyped using oral doses of dextromethorphan 20 mg and mephenytoin 100 mg.
Individual dextrorphan excretion over 8 h and the dextromethorphan/dextrorphan metabolic ratio were calculated. Extensive metabolizers were taken as subjects with a high dextrorphan output (15.56 µmol/8 h) and a low metabolic ratio (0.0023), and poor metabolizers were those with a low dextrorphan output (0.39 µmol/8 h) and a high metabolic ratio (7.00).
Individual 4-hydroxymephenytoin excretion and mephenytoin hydroxylation indices were also determined. Extensive metabolizers eliminated large amounts of 4 hydroxymephenytoin (133.2 µmol/8 h) and had a hydroxylation index of 1.99, and poor metabolizers, because of impaired mephenytoin metabolism, had a high hydroxylation index (277).
The incidence of the poor metabolizer phenotype was 3% for dextromethorphan (95% confidence limits 0.5%–8.5%) and 6% for mephenytoin (95% confidence limits 2%–12.5%).
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Jacqz, E., Dulac, H. & Mathieu, H. Phenotyping polymorphic drug metabolism in the French Caucasian population. Eur J Clin Pharmacol 35, 167–171 (1988). https://doi.org/10.1007/BF00609247
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DOI: https://doi.org/10.1007/BF00609247