Efficacy and Safety of Fondaparinux (ARIXTRA®) in the Initial Treatment of Venous Thromboembolism in Obese Patients.

Background: The MATISSE trials demonstrated that once-daily subcutaneous fondaparinux, a synthetic selective factor Xa inhibitor, was at least as effective and as safe as standard therapies in the initial treatment of deep-vein thrombosis (DVT) or pulmonary embolism (PE). Since obesity is a risk factor for venous thromboembolism (VTE), we analyzed the MATISSE data from the subpopulation of obese patients (body-mass index, BMI ≥30 kg/m²).

Methods: Fondaparinux was administered at a once-daily subcutaneous dose of 7.5 mg (5.0 mg and 10.0 mg in patients <50 kg and >100 kg, respectively). In the MATISSE-DVT trial, fondaparinux was compared with twice-daily subcutaneous enoxaparin (1 mg/kg) in patients with DVT. In the MATISSE-PE trial, it was compared with adjusted-dose intravenous unfractionated heparin (UFH) in patients with PE. All drugs were given for at least 5 days and until anticoagulation with oral anticoagulants was therapeutic. The primary efficacy and safety outcomes were recurrent VTE during 3 months’ follow-up and major bleeding (MB) and death during the initial treatment period.

Results: The percentage of obese patients was 26.3% in MATISSE-DVT and 28.7% in MATISSE-PE (Tables). In both MATISSE-DVT and -PE, efficacy and safety data from obese patients were similar to those from non-obese patients (BMI <30kg/m²). The rates of recurrent VTE and MB in obese patients were not significantly different between fondaparinux and either enoxaparin (MATISSE-DVT) or UFH (MATISSE-PE).

Conclusion: Once-daily fondaparinux is at least as effective and as safe as standard therapies in the initial treatment of DVT or PE in obese patients.