Oxidation Phenotype — A Major Determinant of Metoprolol Metabolism and Response

Abstract

GENETIC polymorphism in the oxidative metabolism of debrisoquine1 is largely responsible for individual differences in its plasma concentration and antihypertensive effect.2 Poor hydroxylators have urinary debrisoquine:4-hydroxydebrisoquine ratios that are higher than 20, whereas extensive hydroxylators have ratios that are less than 12.5.3 , 4 The prevalence of the poor hydroxylator phenotype is about 9 per cent in the United Kingdom3 but it varies widely among ethnic groups, from 1 per cent in Arabs to 30 per cent in Hong Kong Chinese.5 The prevalence of this phenotype in the United States has not been reported, but among whites in Canada it appears to . . .