Metabolism of warfarin enantiomers in Japanese patients with heart disease having different CYP2C9 and CYP2C19 genotypes*

Heterozygotes for CYP2C9 I1e359/Leu allele have reduced in vivo metabolism of (S)-warfarin but not (R)-warfarin. Because (S)-warfarin has a greater anticoagulant potency than its (R)-congener, the genetic polymorphism of CYP2C9 may partly account for the large interpatient variability in therapeutic dosages of warfarin.