Efficacy and bleeding complications among patients randomized to enoxaparin or unfractionated heparin for antithrombin therapy in non-ST-Segment elevation acute coronary syndromes: a systematic overview.

CONTEXT: Antithrombin therapy has become a guidelines-recommended standard of care in the treatment of acute coronary syndromes (ACS), but recent trials comparing use of enoxaparin and unfractionated heparin in ACS have yielded less robust efficacy and safety results than have earlier trials of these antithrombin therapies. OBJECTIVE: To systematically evaluate the end points of all-cause death and nonfatal myocardial infarction (MI), transfusion, and major bleeding observed in the 6 randomized controlled trials comparing enoxaparin and unfractionated heparin in treatment of ACS. DATA SOURCES: The primary data sets for ESSENCE, A to Z, and SYNERGY were available at the Duke Clinical Research Institute. Baseline characteristics and event frequencies for TIMI 11B, ACUTE II, and INTERACT were provided by the principal investigator of each study. STUDY SELECTION: All 6 randomized controlled trials comparing enoxaparin and unfractionated heparin in non-ST-segment elevation ACS were selected for analysis. DATA EXTRACTION: Efficacy and safety end points were extracted from the overall trial populations and the subpopulation receiving no antithrombin therapy prior to randomization. DATA SYNTHESIS: Systematic evaluation of the outcomes for 21 946 patients was performed using a random-effects empirical Bayes model. No significant difference was found in death at 30 days for enoxaparin vs unfractionated heparin (3.0% vs 3.0%; odds ratio [OR], 1.00; 95% confidence interval [CI], 0.85-1.17). A statistically significant reduction in the combined end point of death or nonfatal MI at 30 days was observed for enoxaparin vs unfractionated heparin in the overall trial populations (10.1% vs 11.0%; OR, 0.91; 95% CI, 0.83-0.99; number needed to treat, 107). A statistically significant reduction in the combined end point of death or MI at 30 days was also observed for enoxaparin in the populations receiving no prerandomization antithrombin therapy (8.0% vs 9.4%; OR, 0.81; 95% CI, 0.70-0.94; number needed to treat, 72). No significant difference was found in blood transfusion (OR, 1.01; 95% CI, 0.89-1.14) or major bleeding (OR, 1.04; 95% CI, 0.83-1.30) at 7 days after randomization in the overall safety population or in the population of patients receiving no prerandomization antithrombin therapy. CONCLUSION: In a systematic overview of approximately 22 000 patients across the spectrum of ACS, enoxaparin is more effective than unfractionated heparin in preventing the combined end point of death or MI.

Duration of prophylaxis against venous thromboembolism with enoxaparin after surgery for cancer.

BACKGROUND: Abdominal surgery for cancer carries a high risk of venous thromboembolism, but the optimal duration of postoperative thromboprophylaxis is unknown. METHODS: We conducted a double-blind, multicenter trial in which patients undergoing planned curative open surgery for abdominal or pelvic cancer received enoxaparin (40 mg subcutaneously) daily for 6 to 10 days and were then randomly assigned to receive either enoxaparin or placebo for another 21 days. Bilateral venography was performed between days 25 and 31, or sooner if symptoms of venous thromboembolism occurred. The primary end point with respect to efficacy was the incidence of venous thromboembolism between days 25 and 31. The primary safety end point was bleeding during the three-week period after randomization. The patients were followed for three months. RESULTS: The intention-to-treat analysis of efficacy included 332 patients. The rates of venous thromboembolism at the end of the double-blind phase were 12.0 percent in the placebo group and 4.8 percent in the enoxaparin group (P=0.02). This difference persisted at three months (13.8 percent vs. 5.5 percent, P=0.01). Three patients in the enoxaparin group and six in the placebo group died within three months after surgery. There were no significant differences in the rates of bleeding or other complications during the double-blind or follow-up periods. CONCLUSIONS: Enoxaparin prophylaxis for four weeks after surgery for abdominal or pelvic cancer is safe and significantly reduces the incidence of venographically demonstrated thrombosis, as compared with enoxaparin prophylaxis for one week.