Low molecular weight heparins in the prevention of venous thromboembolism in nonsurgical patients

Hospitalized nonsurgical patients are at risk of developing venous thromboembolic disease (VTED) but, in contrast to surgical patients, only a limited number of prevention trials have been performed. Guidelines for optimal prophylaxis, particularly with respect to low molecular weight heparins (LMWHs), are not definitive. The Fifth American College of Chest Physicians' (ACCP) Consensus on Antithrombotic Therapy makes limited recommendations on the use of LMWH in patients. Recommendations are made for ischemic stroke and general medical patients, but there are insufficient clinical trial data to produce firm recommendations on the use of LMWHs in acute myocardial infarction, pregnancy, and cancer patients. Patients with acute ischemic stroke are at high risk for VTED. The ACCP Consensus recommends employing either low-dose UFH or LMWH. A recent comparison between enoxaparin and UFH revealed an incidence of thromboembolic events in 20% of patients randomized to enoxaparin, compared with 35% in the UFH-treated group. Although the ACCP Consensus states that both low-dose unfractionated heparin (UFH) and LMWH provide effective prophylaxis in general medical patients, particularly those with congestive heart failure and/or pulmonary infections, no specific LMWH or dose is specified. The recently completed Thromboembolism Prevention in Cardiopulmonary Diseases with Enoxaparin (PRINCE) trial compared once-daily enoxaparin with three times daily UFH. Enoxaparin was at least as effective as UFH in reducing the risk of thromboembolic events by 19%. In high-risk pre-defined subgroups with heart failure, enoxaparin was significantly more effective. It is not possible to recommend a specific LMWH for prophylaxis in medical patients, but the recent position adopted by the United States Food and Drug Administration and the World Health Organization that :LMWHs are noninterchangeable drugs suggests that thromboprophylaxis guidelines should be strengthened to reflect the level of evidence for each individual LMWH.