The treatment of patients with deep venous thrombosis (DVT) and pulmonary embolism (PE) has changed recently. Unfractionated heparin had been used to manage these venous thromboembolic disorders, but the introduction of low-molecular-weight heparin changed the way they are managed. The use of low-molecular-weight heparin has the advantage of convenient dosing and can be used as an outpatient therapy, which can lead to lower costs. In previous studies, low-molecular-weight heparin was found to be at least as safe and effective as unfractionated heparin for the initial management of DVT and PE. Most of the studies on this issue are based on managing DVT, and only a few studies have assessed this treatment strategy in patients with PE. Mismetti and colleagues evaluated low-molecular-weight heparin versus unfractionated heparin in the treatment of patients who have DVT with or without associated symptomatic PE.

The authors performed an individual patient data meta-analysis on randomized controlled trials comparing the low-molecular-weight heparin enoxaparin (Lovenox) with unfractionated heparin in the treatment of patients with DVT. To be included in the analysis, the studies had to be randomized properly; include patients with objectively diagnosed DVT with or without symptomatic PE; and use objective measures to confirm major outcomes, including recurrent symptomatic thromboembolism, major bleeding, and death at three months. There was a blind evaluation of clinical events. DVT was confirmed with ultrasonography or venography, and PE was confirmed with a high-probability lung scan, pulmonary angiography, or autopsy. Only those studies that used enoxaparin in a dosage of 1 mg per kg twice per day were included in the meta-analysis.

Three trials met the inclusion criteria for the study. The number of patients enrolled in the combined studies was 749 in the enoxaparin group and 754 in the unfractionated heparin group. Sixteen percent of study participants were diagnosed with PE. When the authors compared the two groups, the relative risk of recurrent venous thrombosis was not significantly different. The results were similar when comparing patients in the two treatment groups who did or did not have a symptomatic PE. With regard to safety, no significant differences existed between the enoxaparin and unfractionated heparin groups, but a trend favoring enoxaparin for reduction in the rate of mortality and major bleeding was noted.

The authors conclude that the low-molecular-weight heparin enoxaparin is as safe and effective as unfractionated heparin in the initial treatment of patients who have DVT with or without PE.