Comparison of ximelagatran, an oral direct thrombin inhibitor, with enoxaparin for the prevention of venous thromboembolism following total hip replacement. A randomized, double-blind study

Abstract

Background: Prophylaxis is recommended following total joint replacement because of the high risk of venous thromboembolism (VTE). Postoperative low-molecular-weight heparin (LMWH) reduces the incidence of venographically detected deep vein thrombosis (DVT) to about 10-15% in total hip replacement (THR) patients. Ximelagatran is a novel, oral direct thrombin inhibitor that selectively and competitively inhibits both free and clot-bound thrombin. We compared the efficacy and safety of ximelagatran with those of enoxaparin for the prevention of VTEin patients undergoing THR. Methods: This was a prospective, randomized, multicenter, double-blind study conducted principally in the USA and Canada. Patients received fixed-dose oral ximelagatran 24 mg bid or subcutaneous enoxaparin 30 mg bid and matched placebo for 7-12 days; both regimens were initiated the morning after surgery. The incidence of VTE(by postoperative day 12) included thrombosis determined by mandatory venography of the leg on which surgery was performed and symptomatic, objectively proven DVT or pulmonary embolism (PE). VTE and bleeding events were interpreted by an independent central adjudication committee for primary analysis. Results: Of the 1838 patients randomized, 1557 had either adequate venography or symptomatic, proven VTE(eficacy population). Overall rate of veno-graphy acceptable for evaluation was 85.4%. Overall rates of total VTEwere 7.9% (62 of 782 patients) in the ximelagatran group and 4.6% (36 of 775 patients) in the enoxaparin group, with an absolute difference of 3.3% and a 95% confidence interval for the difference of 0.9% to 5.7%. Proximal DVT and/or PEoccurred in 3.6% (28 of 782 patients) in the ximelagatran group and 1.2% (nine of 774 patients) in the enoxaparin group. Major bleeding events were observed in 0.8% (seven of 906) of the ximelagatran-treated patients and in 0.9% (eight of 910) of the enoxaparin-treated patients (P > 0.95). Non-inferiority of ximelagatran 24 mg bid based on a prespecified margin of 5% was not met, resulting in superiority of the enoxaparin regimen. Conclusions: Both ximelagatran and enoxaparin decreased the overall rate of VTEcompared with that reported historically. However, in this study, enoxaparin 30 mg bid was more effective than xime-lagatran 24 mg bid for prevention of VTEin THR. Oral xime-lagatran was used without coagulation monitoring, was well tolerated, and had bleeding rates comparable to those of enox-aparin. Further refinement by testing a higher dose of ximelaga-tran in the patients undergoing THR is warranted. © 2003 International Society on Thrombosis and Haemostasis.