Pharmacogenomics and warfarin therapy

(1) Dosing algorithms tailored to individual genetic, demographic, and clinical factors may minimize the risk for bleeding during the initiation of warfarin therapy. (2) Pharmacogenomic testing should be used in addition to (rather than replacing) routine International Normalized Ratio (INR) monitoring. (3) Prospective studies are needed to determine whether pharmacogenomic testing improves patient outcomes, identify which subgroups of patients may benefit, and clarify the risks and costs associated with the use of these tests. Several randomized controlled trials are currently evaluating the impact of pharmacogenomics on dosing accuracy, time to achieve and maintain target INR, incidence of bleeding or thromboembolic events, and monitoring requirements. (4) In August 2007, the FDA updated the product label for warfarin to include genetic variations in CYP2C9 and VKORC1 as one of the factors to consider for more precise initial dosing. Guidelines for pharmacogenomics-based warfarin dosing are under development.