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VKORC1 diplotype-derived dosing model to explain variability in warfarin dose requirements in Asian patients

Edwin Sandanaraj1, Suman Lal, Yin Bun Cheung

  • 1Laboratory of Clinical Pharmacology, Division of Medical Sciences, Humphrey Oei Institute of Cancer Research, National Cancer Centre, Singapore.

Drug Metabolism and Pharmacokinetics
|September 12, 2009
PubMed

Insights

Genetic factors, including VKORC1 diplotypes and CYP2C9 variants, significantly influence warfarin dosing in Chinese patients. Understanding these genetic markers, along with age and weight, can help personalize warfarin therapy and improve patient outcomes.

Area of Science:

  • Pharmacogenomics
  • Clinical Pharmacology
  • Internal Medicine

Background:

  • Warfarin is a widely used oral anticoagulant, but its efficacy is limited by significant inter-patient variability in dose requirements and a risk of bleeding complications.
  • Genetic factors, particularly variations in VKORC1, CYP2C9, and CYP2C19 genes, are known to influence warfarin metabolism and response.

Purpose of the Study:

  • To investigate the impact of VKORC1 diplotypes and CYP2C9/CYP2C19 genetic variants on warfarin disposition and dose requirements in a Chinese patient cohort.
  • To identify key genetic and clinical factors contributing to inter-individual variability in warfarin dosing.

Main Methods:

  • Genotyping of VKORC1, CYP2C9, and CYP2C19 polymorphic variants in 107 Chinese patients.
  • Stratification of weekly warfarin dose requirements and S-warfarin clearance based on identified genotypes and diplotypes.
  • Analysis of the contribution of genetic factors, age, and weight to warfarin dose variability.

Main Results:

  • VKORC1 diplotype status was a major determinant of warfarin dose, with lower doses required for H1-H1 and H1-H(*)a diplotypes compared to H1-H7 and H1-H(*)b diplotypes (P<0.05).
  • VKORC1 diplotype explained 59.1% of the variability in warfarin dose, while CYP2C9 genotype accounted for 6.9%.
  • Patient age and weight were significant covariates, explaining 29% and 8.6% of dose variability, respectively.

Conclusions:

  • VKORC1 diplotype status, CYP2C9 genotype, age, and weight collectively account for 73.4% of inter-individual variability in warfarin dose requirements among Chinese patients.
  • These findings suggest that incorporating pharmacogenetic testing and clinical factors into warfarin dosing guidelines could enhance treatment safety and efficacy.
Abstract

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