Frequent occurrence of CYP2D6*10 duplication allele in a Japanese population.

Allele-specific long-polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (RFLP) and haplotype analysis using XbaI and EcoRI were used to determine whether gene duplication of CYP2D6*10 exists in a Japanese population of 162 healthy subjects. Based on the results of PCR and haplotype analysis, the frequencies of CYP2D6*1X2, CYP2D6*2X2 and CYP2D6*10X2 in the Japanese population were estimated to be 0.3, 0.3 and 0.6%, respectively. The results suggest that duplicated alleles of CYP2D6*10 exist in the Japanese population and that it may be one of the factors affecting the capacity of Japanese to metabolize various CYP2D6 substrate drugs.