WEDNESDAY, Aug. 5 (HealthDay News) -- Apixaban, an inhibitor of factor Xa, was not shown to be non-inferior to enoxaparin for efficacy of thromboprophylaxis following knee replacement, according to research published in the Aug. 6 issue of the New England Journal of Medicine.

Michael Rud Lassen, M.D., of the University of Copenhagen in Horsholm, Denmark, and colleagues analyzed data from 3,195 patients undergoing total knee replacement who were randomized to receive oral apixaban or subcutaneous enoxaparin starting after surgery for 10 to 14 days. A composite of deep-vein thrombosis, nonfatal pulmonary embolism, and death from any cause during treatment was used as the primary efficacy outcome. Patients were evaluated 60 days after the last dose of medication.

The researchers found the rate of outcome was 9 percent in the apixaban group and 8.8 percent in the enoxaparin group, the latter of which was much lower than predicted. However, the incidence of major bleeding and clinically relevant non-major bleeding was 2.9 percent in the apixaban group and 4.3 percent in the enoxaparin group. The incidence of adverse events was similar in both groups.

"Our results support the view that specific factor Xa inhibition has the potential to combine effective thromboprophylaxis with a low risk of bleeding and may have a favorable benefit-to-risk ratio as compared with that for low-molecular-weight heparins," the authors conclude.

Several co-authors reported financial relationships with a variety of companies, including Bristol-Myers Squibb and Pfizer, both of which supported the study.

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