COMPARISON OF THE PREVALENCE OF THE POOR METABOLIZER PHENOTYPE FOR CYP2D6 BETWEEN 203 HMONG SUBJECTS AND 280 WHITE SUBJECTS RESIDING IN MINNESOTA

Genetic polymorphism of the P450IID6 (CYP2D6) enzyme system can be an important component of the variability in response to drug therapy, In terpopulation differences in the prevalence of deficiencies of drug-me tabolizing enzymes may be clinically important in the selection and do sage of drug therapies for patients. Since 1980, the State of Minnesot a has had more than a 1000% increase in population of Hmong refugees f rom Laos. The Hmong are frequently treated in our institution's intern ational clinic with virtually no systematically acquired knowledge abo ut the ability of this relatively ethnically pure population to metabo lize commonly used Western medications. To further our knowledge of dr ug metabolism in this population, we identified the prevalence of the poor metabolizer phenotype for CYP2D6 in a sample population of Hmong subjects and compared this prevalence to that in a sample population o f white subjects. Urine collected after ingestion of dextromethorphan in 237 healthy Hmong and 280 healthy white volunteers was analyzed by HPLC. Based on probit plots of the metabolic ratios (dextromethorphan/ dextrorphan), 8.9% of Hmong subjects and 6.1% of white subjects were a ssigned the poor metabolizer phenotype (difference not significant). W eak associations were found between body surface area and metabolic ra tio for both Hmong and white men and between smoking status and metabo lic ratio for white subjects only. We conclude that the prevalence of poor metabolizers for the CYP2D6 enzyme system is similar between Hmon g subjects and white subjects residing in Minnesota and that an antimo de of 0.3 for metabolic ratio appears to be reasonable for the populat ions studied.