Warfarin dosage adjustment strategy in Chinese population.

BACKGROUND Blood anticoagulation after heart valve replacement is a recognized difficulty all over the world. In this study, we identified the effect of amiodarone on the function of warfarin and confirmed the countermeasure by concluding the genotype distribution of vitamin K epoxide reductase complex 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) of the patient to predict the security dose of warfarin. METHODS Studying on the VKORC1 (-1639G>A) and CYP2C9 genotype of 271 cases on heart valve replacement in the First Affiliated Hospital of Soochow University from Jan. 2012 to Jan. 2014. Warfarin's multivariable regression equation was taken to calculate their warfarin dosage. In the study, 80 of them were selected and divided into 4 groups according to their different warfarin dosage and their usage of amiodaron. The differences of INR values at the 5(th), 8(th), 11(th), 14(th) days of operation were analyzed. RESULTS Among the 80 cases, VKORC1 (-1639G>A) AA types accounted for 90%, and AG types accounted for another 10%, while GG types were not found. In addition that, all of the patients (100%) had CYP2C9*1/*1 type, and CYP2C9*1/*3 had not appeared. There was significant difference in INR values between the groups who used amiodarone or not. The pharmacogenetic equation was accurate in the predicting of the warfarin dosage, so that satisfied anticoagulation efficacy had been achieved in 2 weeks after surgery. CONCLUSION It is necessary for the patients to do the warfarin pharmacogenetic test to get the suitable dose before heart valve replacement. Amiodarone can enhance the anticoagulant efficacy of warfarin, so the dosages of warfarin should be reduced properly because of the medicine combination, and INR values must be monitored more frequently to make the anticoagulant process secure and efficient.