Objective: To discuss the role of low-molecular-weight heparins (LMWHs) in the prevention of venous thromboembolism (VTE) in medical and orthopedic surgery patients. VTE prophylaxis trials in these practice settings establishing the current use of LMWHs marketed in the US are included. An overview is also provided of VTE incidence, risk factors, and prophylaxis consensus guidelines.
Data sources and study selection: Clinical trials, review articles, and meta-analyses for Food and Drug Administration-approved LMWHs were identified from a MEDLINE search (1980-March 2002). Search terms included dalteparin, enoxaparin, internal medicine, low-molecular-weight heparin, orthopedic surgery, risk factors, tinzaparin, and venous thromboembolism.
Data synthesis: Consensus guidelines are useful as an initial guide to appropriate VTE prophylaxis; however, a review of the primary literature is needed to identify optimal agents, regimens, or interventions. LMWHs have demonstrated sound efficacy in VTE prevention; however, the quantity and quality of literature are not always comparable for the available agents.
Conclusions: Enoxaparin has demonstrated efficacy and safety in VTE prevention in medical patients, whereas information is limited or lacking for dalteparin and tinzaparin. Total hip replacement (THR) trials have been conducted with all US-marketed LMWHs and have demonstrated the efficacy and safety of each agent. Trials specifically establishing the efficacy of an LMWH in total knee replacement surgery (TKR) have been published for enoxaparin. One combination THR and TKR trial has been published for tinzaparin. These trial outcomes have positioned the LMWHs as key alternatives to adjusted-dose warfarin for VTE prophylaxis in orthopedic surgery. Inherent differences between LMWHs prevent the extrapolation of clinical outcomes from 1 trial to another.