New Regimen with Old Drug Slashes Blood-Clot Risk by 64%

A study has found that low-dose treatment with warfarin (Coumadin) is not only safe but highly effective for prolonged use in patients who are prone to clots of unknown origin (deep vein thrombosis) in their legs or lungs, cutting the risk of clots alone by 64%.

Because of the dramatic findings, a multicenter study was halted and the findings, initially scheduled for later publication, were posted on the website of The New England Journal of Medicine on February 24, 2003.

Standard practice has been to treat patients who have had a blood clot in their legs or lungs with warfarin for three to six months only, because it can be dangerous and has a relatively high side-effect rate. About 20-25% of these patients will have another blood clot after the warfarin is stopped.

The new study involved 508 patients who suffered blood clots for no apparent reason and had received full-dose anticoagulation therapy for at least three months. One group received placebo and the other group continued to take a small maintenance dose of warfarin, about half the normal dose. This dose was found not to increase the risk of major bleeding; to decrease the clot risk by 64%; and the risk of clots, major internal bleeding, or death altogether by 48%. The other advantages of warfarin are that it has been in use for around 50 years and is available in a cheap generic form.

"For ethical reasons, we stopped the study three years ahead of schedule so that all patients with blood clots of unknown origin would get the chance to go on low-dose warfarin,” said Dr. Stephen Moll, director of the thrombophilia program at the University of North Carolina at Chapel Hill (www.unc.edu) and one of the principal investigators in the trial. The university was a participating center in the trial, which was supported by the US National Heart, Lung, and Blood Institute.




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