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• Meloxicam is a substrate for the CYP2C9 and CYP3A4 enzymes. • We have previously reported that the frequency of the CYP2C9*1/*13 genotype in the Korean population is 1.1%. • The CYP2C9*1/*13 genotype is associated with decreased metabolism and increased pharmacodynamic effects of meloxicam. • This is the first report that evaluates the in vivo effects of the CYP2C9*13 allele on the pharmacokinetics and pharmacodynamics of CYP2C9 substrates with a sufficient sample size. To determine the effects of the CYP2C9*1/*13 genotype on the pharmacokinetics and pharmacodynamics of meloxicam in Korean subjects. Meloxicam (15 mg) was orally administered to 21 healthy Korean volunteers with either the CYP2C9*1/*1 or the CYP2C9*1/*13 genotype. Plasma meloxicam concentrations were analysed by HPLC-UV for 72 h after drug administration. The pharmacodynamic effects of meloxicam were determined by measuring TXB generated in blood. The AUC(0,∞) and C of meloxicam were 2.43- and 1.46-fold higher in the CYP2C9*1/*13 group than in the CYP2C9*1/*1 group, respectively. The oral clearance of meloxicam was significantly lower in the CYP2C9*1/*13 group (37.9% of wild type) than in the CYP2C9*1/*1 group. The t of meloxicam was 1.84-fold longer in the CYP2C9*1/*13 group than in the CYP2C9*1/*1 group. The rate of TXB production was significantly lower in the CYP2C9*1/*13 group than in the CYP2C9*1/*1 group. The CYP2C9*1/*13 genotype is associated with decreased metabolism and increased pharmacodynamic effects of meloxicam. [ABSTRACT FROM AUTHOR]

Aims To determine the frequencies of the variant alleles and the genotypes of CYP2C9 in a Korean population. Methods Three hundred and fifty-eight healthy Korean subjects were studied. CYP2C9 alleles were detected by polymerase chain reaction-restriction fragment length polymorphism assays and direct sequencing assays. Results The allele frequencies were 0.934 for CYP2C9* 1, 0.060 for CYP2C9* 3 and 0.006 for CYP2C9* 13. The CYP2C9*2,* 4,* 5 and * 11 alleles were not detected. The frequencies of the CYP2C9* 1/* 1, * 1/* 3 and * 1/* 13 genotypes were 0.869, 0.120 and 0.011, respectively. Conclusion The frequency of the CYP2C9* 3 allele in the Korean population studied was significantly higher than reported elsewhere, and a novel allele, CYP2C9* 13, was found at a frequency of 0.006 (95% confidence interval 0, 0.012). Only three genotypes of CYP2C9, CYP2C9* 1/* 1,* 1/* 3 and * 1/* 13 were observed in this Korean population. [ABSTRACT FROM AUTHOR]