Clinical Question: Is enoxaparin as effective as unfractionated heparin in patients with non–ST-segment elevation acute coronary syndromes?

Setting: Various (meta-analysis)

Study Design: Systematic review

Synopsis: In all six of the major randomized controlled trials that compared enoxaparin with unfractionated heparin, including two new trials published in the same issue (JAMA July 7, 2004;292:45–54, and 292:55–64), investigators systematically evaluated the outcomes of treatment with these medications. A total of 21,946 patients were involved in the six trials.

At 30 days, no significant differences were observed in all-cause mortality between enoxaparin and unfractionated heparin, but a significantly lower risk for the combined end point of death or nonfatal myocardial infarction at 30 days occurred in the enoxaparin group (10.1 versus 11 percent; number needed to treat [NNT] = 107). In patients who did not receive prerandomization anti-thrombin therapy (i.e., aspirin or tirofiban), the combined end point of death or myocardial infarction at 30 days also was reduced more in the enoxaparin group than in the unfractionated heparin group (8.0 versus 9.4 percent; NNT = 72). No significant differences were noted in major bleeding complications between treatment groups.

Bottom Line: Enoxaparin is as effective as and may be minimally superior to unfractionated heparin for the treatment of non–ST-segment elevation acute coronary syndromes. Patients who are not already receiving anti-thrombin therapy with aspirin or tirofiban are more likely to benefit from enoxaparin therapy. (Level of Evidence: 1a)