The Accuracy Of Warfarin Dosage Based On VKORC1and CYP2C9

Background: Warfarin, a Coumadin derivative, is the most prescribed anticoagulantworldwide which has a narrow therapeutic window. Warfarin is metabolized by the hepaticcytochrome P450enzyme expressed by the CYP2C9gene. Warfarin’s anticoagulant effectis mediated by the enzyme VKORC1, which is the target enzyme inhibited by warfarin.Variation in the CYP2C9gene causes some patients to have slow metabolism of warfarinand a longer half-life the drug, resulting in higher than usual blood concentrations ofwarfarin and greater anticoagulant effect.Objective：The aim of this study is to assess the accuracy of warfarin dosage based onVKORC1and CYP2C9.Methods: Blood samples were taken from44patients. We compared the warfarin dosagebetween on genotype (according to www.warfarindosing.org) and treatment dosage withINR value within2.0-3.0.Results: The majority Chinese people on our study had VKORC1homozygous AA(90.9%), rarely had VKORC1heterozygous AG (9.1%), and we cannot find a patient withhomozygous GG. For CYP2C9genotype, mostly patients had wildtype variant(CYP2C9*2CC and CYP2C9*3AA). The warfarin dosage for patients with VKORC1AAand CYP2C9*3AC is lower than the others genotype variant.Conclusion: There is no significant difference between pharmacogenetic algorithm(www.warfarindosing.org) and our treatment dosage. Our conclusion is pharmacogeneticalgorithm is accurate to predict the warfarin dose.