Influence of the CYP2D6*10 allele on the metabolism of mexiletine by humanliver microsomes

Aims To study the influence of CYP2D6*10 on the formation of p-hydroxymexil etine (PHM) and hydroxymethylmexiletine (HMM) using microsomes from human l iver of known genotypes. Methods Microsomes from human livers of genotype CYP2D6*1/*1 (n = 5), *1/*1 0 (n = 6) and *10/*10 (n = 6) were used in this study. The formation of PHM and HMM was determined by high-performance liquid chromatography. Results The formation rates of PHM and HMM were decreased by more than 50% and 85% in CYP2D6*1/*10 and *10/*10 microsomes, respectively, compared with *1/*1 microsomes. Concl(u)sions The metabolism of mexiletine to form PHM and HMM appears to b e impaired to a significant extent in human liver microsomes from hetero- a nd homozygotes of CYP2D6*10.