Efficacy and safety of enoxaparin to prevent deep vein thrombosis after hip arthroplasty.

Four clinical studies were conducted in the United States and Canada to compare the efficacy and safety of Enoxaparin, a low molecular weight heparin, with low dose unfractionated heparin and placebo for the prevention of deep venous thrombosis after hip arthroplasty. In each study, patients were randomized consecutively into treatment groups of placebo, unfractionated heparin (5000 IU 3 times daily or 7500 IU twice daily), or Enoxaparin (30 mg twice daily, 40 mg once daily, or 10 mg once daily), with treatment started postoperatively. All patients had noninvasive studies and bilateral lower extremity radiocontrast venography at the end of study treatment or on discharge from the hospital (not applicable to the first 24 patients enrolled in the Canada-1 study). One thousand nine hundred forty patients were treated, and 1937 patients were included in efficacy analysis. The incidence of total deep venous thrombosis was as follows: placebo group, 46% (22 of 50 patients); heparin group, 16% (87 of 539 patients); Enoxaparin group, 30 mg twice daily 12% (93 of 785 patients); Enoxaparin 40 mg daily group, 14% (14 of 402 patients); and Enoxaparin 10 mg daily group, 25% (40 of 161 patients). Incidence of proximal deep venous thrombosis was 22%, 5%, 4%, 4%, and 11%, respectively. Major bleeding events were reported in 4% of the placebo group, 2% to 4% in the Enoxaparin group, and 6% in the unfractionated heparin group. In these clinical studies, Enoxaparin, 30 mg twice daily, was shown to be as effective and safe as low dose unfractionated heparin to prevent deep venous thrombosis after hip arthroplasty.