Population differences in S‐warfarin metabolism between <i>CYP2C9</i> genotype‐matched Caucasian and Japanese patients

Abstract

These findings indicate that population differences in the frequencies of known variant CYP2C9 alleles account only in part for the variability observed in in vivo CYP2C9 activity in different populations. In addition, a gene-dose effect of defective CYP2C9 alleles on the in vivo CYP2C9 activity is evident in Japanese patients but not in Caucasian patients. Further studies are required to identify currently unknown factor(s) (eg, transcriptional regulation) responsible for the large intrapopulation and interpopulation variability in CYP2C9 activity.