Metabolism of warfarin enantiomers in Japanese patients with heart disease having different CYP2C9 and CYP2C19 genotypes.
OBJECTIVE
To determine whether genetic polymorphism of cytochrome P450 (CYP) 2C9 affects the in vivo metabolism of warfarin enantiomers.


METHODS
Eighty-six Japanese patients heart disease who were given warfarin participated in the study. Plasma unbound concentrations of warfarin enantiomers and urinary (S)-7-hydroxywarfarin concentrations were measured by means of a chiral HPLC and ultrafiltration technique to calculate the unbound oral clearance (CLpo,u) for the enantiomers and the formation clearance (CLm) for (S)-warfarin 7-hydroxylation. Genotyping for CYP2C9 (the wild type [wt], Arg144/Cys, and I1e359/Leu) and for CYP2C19 (wt, ml, and m2) was performed with a polymerase chain reaction method.


RESULTS
Three patients were heterozygous for the CYP2C9 Leu359 mutation but none were homozygous for the mutation (the allele frequency of 0.017). None had a CYP2C9 Cys144 allele. The medians for (S)-warfarin CLpo,u and its 7-hydroxylation CLm obtained from heterozygotes of CYP2C9 Leu359 were significantly less than those obtained from homozygotes of the wt allele, as follows: 234 ml/min (range, 156 to 269 ml/min) versus 632 ml/min (range, 180 to 2070 ml/min) (p < 0.001) and 0.20 ml/min (range, 0.05 to 0.77 ml/min) versus 0.80 ml/min (range, 0.05 to 14.9 ml/min) (p < 0.05), respectively. In contrast, no difference was observed in (R)-warfarin CLpo,u between the groups. The allele frequencies for CYP2C19 m1 and CYP2C19 m2 were 0.26 and 0.14, respectively, indicating 15% of patients were genotypically poor metabolizers of CYP2C19. No difference in CLpo,u for warfarin enantiomers was observed between the assumed CYP2C19 phenotypes.


CONCLUSIONS
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.
Takahashi
H
H
Department of Pharmacotherapy, Meiji College of Pharmacy, Tokyo, Japan.
Kashima
T
T
Nomizo
Y
Y
Muramoto
N
N
Shimizu
T
T
Nasu
K
K
Kubota
T
T
Kimura
S
S
Echizen
H
H
D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D001189:Aryl Hydrocarbon Hydroxylases; D065731:Cytochrome P-450 CYP2C19; D065729:Cytochrome P-450 CYP2C9; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D005260:Female; D005838:Genotype; D006331:Heart Diseases / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007564:Japan; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D013237:Stereoisomerism; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics*; D014859:Warfarin / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics
D000925:Anticoagulants; D014859:Warfarin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D013250:Steroid Hydroxylases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D039181:Steroid 16-alpha-Hydroxylase