Distribution of CYP2C9*13 allele in the Chinese Han and the long‐range haplotype containing CYP2C9*13 and CYP2C19*2

Cytochrome P450 2C9 ( CYP2C9 ) and CYP2C19 , located in tandem on chromosome 10q23–24, are known as genetically polymorphic. CYP2C9*13 is an important CYP2C9 variant in Asian populations, and is correlated with the reduced plasma clearance of some clinically important drugs. In this research, the allele frequency of CYP2C9 * 13 was determined to be 0.42% (95% CI of 0.17% to 0.86%) in 839 Chinese Han, male subjects. All detected subjects with CYP2C9 * 13 carry the CYP2C19 * 2 allele, too. Sequencing results infer the CYP2C9 * 13 haplotype, which contains eight linked SNPs, originates from the CYP2C9 *1B haplotype group. CYP2C9 *1B has been reported to be linked with CYP2C19*2 . These indicate a long‐range haplotype containing the CYP2C9*13 and CYP2C19*2 mutation, which means most CYP2C9*13 carriers will carry the CYP2C19*2 allele and the six SNPs of the CYP2C9 *1B haplotype group, and may have more reduced intrinsic clearance of drugs such as phenytoin, tolbutamide and chlorpropamide that are metabolized by both CYP2C9 and CYP2C19. Copyright © 2012 John Wiley & Sons, Ltd.