CYP2C19 genotype and S-mephenytoin 4'-hydroxylation phenotype in a Chinese Dai population

Eur J Clin Pharmacol. 2002 Apr;58(1):15-8. doi: 10.1007/s00228-002-0425-x. Epub 2002 Feb 22.


Aims: To investigate the incidence of the CYP2C19 polymorphism in the Chinese Dai population.

Methods: One hundred and ninety-three healthy Chinese Dai volunteers were identified with respect to CYP2C19 by genotype and phenotype analyses. A polymerase chain reaction-restriction fragment length polymorphism method was performed for genotyping procedures. The 4'-hydroxymephenytoin (4'-OH-MP) and S/R-mephenytoin ( S/R-MP) excreted in the urine were determined by high-performance liquid chromatography and gas chromatography, respectively.

Results: Eighteen subjects were identified as poor metabolisers (PMs). The frequency of PMs in the Chinese Dai subjects was 9.3% (95% confidence interval 5.2, 13.4), which is lower than that in the Chinese Han population ( P<0.05). Chinese Dai subjects had a higher frequency of the mutant CYP2C19*2 allele (0.303) and a lower frequency of the mutant CYP2C19*3 allele (0.034). These two mutant alleles could explain all deficiencies of CYP2C19 activity in the Chinese Dai subjects. The frequency of the CYP2C19*3 allele is significantly lower than that in the Chinese Han population ( P<0.05). The mean S/R ratio was lower in the homozygous extensive metabolisers (EMs) compared with that in heterozygous EMs ( P<0.01), and the latter was lower than that in the PMs ( P<0.01). Furthermore, the mean S/R ratio in CYP2C19*3/ CYP2C19*2 heterozygous PMs was possibly lower than that in the CYP2C19*2/ CYP2C19*2 homozygous PMs ( P<0.05).

Conclusion: The frequencies of PMs and CYP2C19*3 allele in the Chinese Dai population are significantly lower than those in the Han population. The CYP2C19 genotype analysis is largely consistent with the mephenytoin phenotype analysis. The variability of S/R ratios in EMs and PMs shows a gene-dosage effect.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Anticonvulsants / metabolism*
  • Anticonvulsants / urine
  • Aryl Hydrocarbon Hydroxylases*
  • China
  • Cytochrome P-450 CYP2C19
  • Cytochrome P-450 Enzyme System / genetics*
  • Cytochrome P-450 Enzyme System / metabolism*
  • Female
  • Genotype
  • Humans
  • Hydroxylation
  • Male
  • Mephenytoin / metabolism*
  • Mephenytoin / urine
  • Mixed Function Oxygenases / genetics*
  • Mixed Function Oxygenases / metabolism*
  • Phenotype
  • Polymorphism, Genetic
  • Stereoisomerism


  • Anticonvulsants
  • Cytochrome P-450 Enzyme System
  • Mixed Function Oxygenases
  • Aryl Hydrocarbon Hydroxylases
  • CYP2C19 protein, human
  • Cytochrome P-450 CYP2C19
  • Mephenytoin