Venous thromboembolism is a condition which causes clotting in the veins. Typical therapy for venous thromboembolism includes a five- to 10-day course of heparin followed by three to 12 months of the oral drug warfarin. However, the problem with this treatment is that once the patient goes off warfarin, venous thromboembolism recurs. While recurrence rates of this problem are reduced if the patient stays on warfarin, according to previous studies, it also puts the patient at an increased risk for a major hemorrhage. Researchers have now conducted a study to find out whether keeping patients on a low-dose of warfarin would be beneficial or too much of a risk.
The study included more than 500 patients who received standard treatment and then were assigned to receive a placebo or low-intensity warfarin. Participants were followed to see who had recurrent venous thromboembolism, major hemorrhage, and who died. After four years, researchers found that 37 of the 253 patients assigned to the placebo had recurrent venous thromboembolism, as compared with 14 of the 255 patients on the low-intensity warfarin. This indicated a risk reduction of 64 percent. Furthermore, major hemorrhage occurred in two patients on the placebo and five on the warfarin. Researchers claimed that the reduction in the risk of recurrent venous thromboembolism for patients on low-intensity warfarin, after adjusting for other factors, was between 76 percent and 81 percent.
Andrew Schafer, M.D., from the University of Pennsylvania School of Medicine, in an accompanying editorial said that though researchers claim short-term treatment reduces the risk of recurrent venous thromboembolism by up to 81 percent, doctors are continuing to walk a tightrope for dosing medicine for patients with venous thromboembolism. Although low-intensity warfarin may prevent recurrent venous thromboembolism it is unclear what dosage doctors need to give to prevent recurrence and not cause major bleeding.