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By Nancy Jackson, HealthAtoZ contributing writer
A study examining the long-term use of a low dose of warfarin to prevent deep-vein blood clots found that the therapy worked without causing any significant problems. These clots in deep veins in the legs can break off and travel to the lungs, which can lead to a pulmonary embolism (a potentially deadly blood clot in the lungs).
Previously, patients at risk of this condition were treated with five to 10 days of a drug called heparin followed by three to six months on a standard dose of warfarin, a drug to prevent blood clotting. Because a major side effect of warfarin is significant bleeding, the standard dose is usually prescribed for about six months.
The PREVENT study examined 508 patients who were 30 or older and had experienced deep vein thrombosis (DVT) or a pulmonary embolism within the previous two years. Of those, 253 patients were assigned to a placebo, and 37 of them had a recurring episode, compared to just 14 of the 255 patients taking a low-dose of warfarin - a 64 percent reduction in the risk of a new episode. There were eight deaths in the placebo group, but only four in the warfarin group. The study followed the patients for as long as four years, with an average of two years.
That's plenty of time for any significant bleeding problems to show up, says Dr. Yves Rosenberg, medical officer in clinical trials for the National Heart, Lung, and Blood Institute and a study co-author of the study called PREVENT (Prevention of Recurrent Venous Thromboembolism). The bleeding problem didn't show up. Only five of the patients taking warfarin had serious bleeding problems.
These results are welcome news to the half million Americans every year who experience DVT or a pulmonary embolism. Risk factors include trauma or surgery that result in people not able to move their legs, increasing the risk of blood coagulating in the legs. Being immobile increases the risk, and even taking a long car trip or plane trip without taking enough time to get up and move around, can cause a clot to form in the veins of the legs. Also, smokers, people who are obese, people with high blood pressure and the elderly are at higher risk for DVT, as well as women taking the hormone estrogen.
DVT can be deadly. Unfortunately the symptoms of DVT can be misdiagnosed, Rosenberg says. "If it's not treated quickly, you risk complications of pulmonary embolism," Rosenberg says. "In pulmonary embolism, the clot detaches in the leg and goes to the lung and stops circulation. It causes major problems and results in death in a significant number of cases."
Symptoms of a pulmonary embolism include:
- Sudden shortness of breath.
- Sharp chest pain.
- Cough with bloody sputum.
- Excessive sweating.
- Rapid pulse.
- Lightheadedness.
This article was reviewed and updated June 2007.
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