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Researchers compare medications for stroke prevention in patients with atrial fibrillation

The 2.3 million individuals in the United States with atrial fibrillation (AF, fast and irregular heart beat) have a five-fold increased risk of ischemic stroke. A recent study supported in part by the Agency for Healthcare Research and Quality (HS10133) compared the effectiveness and costs of three stroke prevention therapies for patients with chronic AF: warfarin, ximelagatran, and aspirin.

Warfarin has been shown to reduce the risk of ischemic stroke by 65 percent in AF patients, but it has been associated with drug and food interactions, slow onset of action, the need for regular monitoring, and individual variability in metabolism. Ximelagatran, which was developed to overcome these problems, has been shown to be as effective as warfarin in stroke prevention with less bleeding in patients with chronic AF.

Unlike warfarin, ximelagatran can be taken in a fixed, oral dose and does not require monitoring of prothrombin time. Although it may lower the risk of intracranial hemorrhage, previous studies found that 6 to 7 percent of patients taking ximelagatran developed liver function abnormalities. Patients who have a major risk for hemorrhage often take aspirin instead of ximelagatran or warfarin.

Cara L. O'Brien, M.D., and Brian F. Gage, M.D., M.Sc., of the Washington University School of Medicine, used a decision model to compare costs and benefits of ximelagatran, warfarin, and aspirin in a hypothetical group of 70-year-old patients with chronic AF. For AF patients at the lowest stroke rate, only aspirin was cost effective. In contrast, for AF patients with additional stroke risk factors and low hemorrhage risk, ximelagatran modestly increased quality-adjusted survival (0.12 quality-adjusted life year, QALY), but at a substantial cost ($116,000 per QALY) compared with warfarin. For ximelagatran to cost less than $50,000 per QALY, it would have to cost less than $1,100 per year or be prescribed to those patients who have either an elevated risk of intracranial hemorrhage (over 1 percent per year on warfarin) or a low quality of life with warfarin therapy.

See "Costs and effectiveness of ximelagatran for stroke prophylaxis in chronic atrial fibrillation," by Drs. O'Brien and Gage, in the February 9, 2005, Journal of the American Medical Association 293(6), pp. 699-706.

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