US researchers said Wednesday they have found gene variations which predict how a patient will react to the drug warfarin, widely used to prevent blood clotting and treat heart attack victims.
Researchers found that the gene VKORC1 has a key role in predicting how sensitive a patient will be the blood thinning drug in the first week of using the drug -- helping doctors deal with the wide variation in responses to the drug.
Studying nearly 300 patients starting therapy with warfarin, the researchers found that variations in VKORC1 can explain why individual patients need greater or smaller doses of the drug to best benefit from it.
Warfarin, sold under the brand names Coumadin and Jantoven -- is used by patients suffering from thrombosis, the tendency to form clots in their blood vessels, and by those already suffering from clots.
Some two million people in the United States take it regularly, especially after having suffered heart attacks, according to a summary of the research.
"Despite its wide use, physicians find the drug challenging to prescribe because individuals' responses vary widely, and too high of a dose can result in excessive bleeding while too low a dose could allow dangerous blood clots to form," the summary said.
The study was conducted by Vanderbilt University researchers associated with the Pharmacogenetics Research Network of the US National Institutes of Health.
The research is published in the March 6 issue of the New England Journal of Medicine.