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 . . .