Author: Anna D. Garrett, PharmD, BCPS, CPP

The FDA has approved updated labeling for warfarin products. The labeling change highlights the opportunity for health care providers to use genetic tests to improve their initial estimate of a reasonable warfarin dose for individual patients. Testing may help optimize the use of warfarin and lower the risk of bleeding complications from the drug. These labeling updates are based on an analysis of recent studies that found different people respond to the drug differently based, in part, on whether they have variations of certain genes.

The FDA estimates that 2 million patients start taking warfarin in the United States every year to prevent blood clots, heart attacks, and stroke. One third of patients receiving warfarin metabolize it quite differently than expected. Research has shown that some of the unexpected response to warfarin depends on a patient's variants of the genes CYP2C9 and VKORC1. According to an FDA spokesman, the labeling change is one step toward the agency's commitment to personalized medicine. This initiative makes use of pharmacogenomics-the science that predicts a response to drugs based upon a person's genetic makeup.