HealthDay News – In thrombotic antiphospholipid antibody syndrome (APS), rivaroxaban is not noninferior to dose-adjusted vitamin K antagonists (VKAs), according to a study published online October 15 in the Annals of Internal Medicine.

Josep Ordi-Ros, MD, PhD, from the Vall d’Hebrón Research Institute in Barcelona, Spain, and colleagues conducted a 3-year noninferiority trial at 6 university hospitals in Spain. A total of 190 adults with thrombotic APS were randomly assigned to rivaroxaban or dose-adjusted VKAs.

The researchers found that recurrent thrombosis occurred in 11.6 and 6.3% of patients in the rivaroxaban and VKA groups, respectively, after 3 years of follow-up (risk ratio in the rivaroxaban group, 1.83; 95% confidence interval, 0.71 to 4.76). Stroke occurred more often in patients receiving rivaroxaban versus VKAs (nine versus zero events; corrected risk ratio, 19.00; 95% confidence interval, 1.12 to 321.9). Major bleeding occurred in 6.3 and 7.4% of patients in the rivaroxaban and VKA groups, respectively (risk ratio, 0.86; 95% confidence interval, 0.30 to 2.46). Rivaroxaban-treated patients with previous arterial thrombosis, livedo racemosa, or APS-related cardiac valvular disease were more likely to have an increased risk for recurrent thrombosis.

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“The primary efficacy analyses could not demonstrate rivaroxaban noninferiority to dose-adjusted VKAs,” the authors write. “In fact, although inconclusive, we found an increased risk for recurrent thrombosis in the rivaroxaban group, with a predominance of arterial thrombotic events and stroke in particular.”

Several authors disclosed financial ties to pharmaceutical companies, including Bayer Hispania, which funded the study.

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