Safety and efficacy of enoxaparin vs unfractionated heparin in patients with non-ST-segment elevation acute coronary syndromes who receive tirofiban and aspirin: A randomized controlled trial

Context: Enoxaparin or the combination of glycoprotein IIb/IIIa inhibitor tirofiban with unfractionated heparin independently have shown superior efficacy over unfractionated heparin alone in patients with non-ST-elevation acute coronary syndromes (ACS). It is not clear if combining enoxaparin with glycoprotein IIb/IIIa inhibitors is as safe or as effective as the current standard combination of unfractionated heparin with glycoprotein IIb/IIIa inhibitors. Objective: To assess efficacy and safety of the combination of enoxaparin and tirofiban compared with unfractionated heparin and tirofiban in patients with non-ST-elevation ACS. Design, Setting, and Participants: A prospective, international, open-label, randomized, noninferiority trial of 1 mg/kg of enoxaparin every 12 hours (n=2026) compared with weight-adjusted intravenous unfractionated heparin (n=1961) in patients with non-ST-elevation ACS receiving tirofiban and aspirin. Phase A of the A to Z trial was conducted between December 1999 and May 2002. Main Outcome Measures: Death, recurrent myocardial infarction, or refractory ischemia at 7 days in the intent-to-treat population with boundaries set for superiority and noninferiority. Safety based on measures of bleeding using the Thrombolysis in Myocardial Infarction (TIMI) classification system. Results: A total of 169 (8.4%) of 2018 patients randomized to enoxaparin experienced death, myocardial infarction, or refractory ischemia at 7 days compared with 184 (9.4%) of 1952 patients randomized to unfractionated heparin (hazard ratio [HR], 0.88; 95% confidence interval [CI], 0.71-1.08). This met the prespecified criterion for non-inferiority. All components of the composite primary and secondary end points favored enoxaparin except death, which occurred in only 1% of patients (23 for enoxaparin and 17 for unfractionated heparin). Rates for any TIMI grade bleeding were low (3.0% for enoxaparin and 2.2% for unfractionated heparin; P=.13). Using a worst-case approach that combined 2 independent bleeding evaluations, use of enoxaparin was associated with 1 additional TIMI major bleeding episode for each 200 patients treated. Conclusions: In patients receiving tirofiban and aspirin, enoxaparin is a suitable alternative to unfractionated heparin for treatment of non-ST-elevation ACS. The 12% relative and 1% absolute reductions in the primary end point in favor of enoxaparin met criterion for noninferiority and are consistent with prior trials performed without the use of glycoprotein IIb/IIIa inhibitors.