Fondaparinux as Alternative Anticoagulant to Warfarin or Low-Molecular-Weight Heparin for Recurrent Venous Thrombosis

Abstract

Recurrent venous thromboembolism (VTE) occurs in some patients despite treatment with the standard drugs, warfarin and low-molecular-weight heparin (LMWH). Fondaparinux is currently licensed by the Food and Drug Administration for the prophylaxis of deep-vein thrombosis in patients undergoing orthopedic or abdominal surgery and also in the treatment of VTE. Well-documented use of this agent beyond these indications and for prolonged periods is currently limited. Two cases of "refractory" VTE, managed effectively with long-term fondaparinux are described. In the first case, a 43-year-old man developed recurrent thrombosis while receiving warfarin at a higher target international normalized ratio (INR) of 3 to 4. In the second case, a 45-year-old man developed recurrent thrombosis on once-daily dalteparin. Both the patients were successfully managed with fondaparinux for 36 months and 14 months, respectively, with no sign of recurrent thrombosis or adverse effects. In patients with recurrent VTE, fondaparinux is effective as daily injections as much as twice-daily LMWH or warfarin maintained on higher therapeutic-range INRs. Although the exact mechanism for this effectiveness is not yet understood, it provides a useful alternative to the standard therapies. In addition, the side effect profile is also favorable for fondaparinux, in that it causes less thrombocytopenia and skin reactions in comparison with heparins. Daily fondaparinux injections may be an effective antithrombotic agent in patients who develop recurrent VTE on anticoagulation with warfarin or LMWH.