2007 Volume 29 Issue 6 Pages 721-725
Warfarin is the most widely prescribed oral anticoagulant, but there is greater than 10-fold interindividual variability in the dose required to attain a therapeutic response. Pharmacogenetic analysis of two genes, the warfarin metabolic enzyme CYP2C9 and warfarin target enzyme, vitamin K epoxide reductase complex 1 VKORC1, confirmed their influence on warfarin maintenance dose. The contribution to inter-individual variation in warfarin dose in our patients on stable anticoagulation with a target International Normalized Ratio of 1.6-2.6 was 5.9% for VKORC1-1639G>A and 5.2% for CYP2C9 42613A>C. Recent studies have shown that VKORC1 haplotype and CYP2C9 genotypes predicted about 40% of the individual variations of warfarin dose. Including non-genetic factors such as age, sex, weight and drug interactions with genotype information predicted more than 50% of warfarin dosing variability.
Aspirin reduces the risk of cardiovascular events in patients with atherosclerotic diseases. However, its effectiveness is limited because a significant portion of the patients with arterial thrombosis who are treated with aspirin has a recurrent event. This is designated as aspirin resistance. To understand aspirin resistance and to develop the effective monitoring system of aspirin effectiveness, we are conducting the Study on Profile and Genetic factors of Aspirin Resistance: ProGEAR Study.
