A comparison of enoxaparin with placebo for the prevention of venous thromboembolism in acutely ill medical patients

Background The efficacy and safety of thromboprophylaxis in patients with a cute medical illnesses who may be at risk for venous thromboembolism have n ot been determined in adequately designed trials. Methods In a double-blind study, we randomly assigned 1102 hospitalized pat ients older than 40 years to receive 40 mg of enoxaparin, 20 mg of enoxapar in, or placebo subcutaneously once daily for 6 to 14 days. Most patients we re not in an intensive care unit. The primary outcome was venous thromboemb olism between days 1 and 14, defined as deep-vein thrombosis detected by bi lateral venography (or duplex ultrasonography) between days 6 and 14 (or ea rlier if clinically indicated) or documented pulmonary embolism. The durati on of follow-up was three months. Results The primary outcome could be assessed in 866 patients. The incidenc e of venous thromboembolism was significantly lower in the group that recei ved 40 mg of enoxaparin (5.5 percent [16 of 291 patients]) than in the grou p that received placebo (14.9 percent [43 of 288 patients]) (relative risk, 0.37; 97.6 percent confidence interval, 0.22 to 0.63; P< 0.001). The benef it observed with 40 mg of enoxaparin was maintained at three months. There was no significant difference in the incidence of venous thromboembolism be tween the group that received 20 mg of enoxaparin (15.0 percent [43 of 287 patients]) and the placebo group. The incidence of adverse effects did not differ significantly between the placebo group and either enoxaparin group. By day 110, 50 patients in the placebo group had died (13.9 percent), 51 i n the 20-mg group had died (14.7 percent), and 41 in the 40-mg group had di ed (11.4 per cent); the differences were not significant. Conclusions Prophylactic treatment with 40 mg per day of enoxaparin subcuta neously safely reduces the risk of venous thromboembolism in patients with acute medical illnesses. (N Engl J Med 1999;341: 793-800.) (C)1999, Massach usetts Medical Society.