Low-molecular-weight heparins and new strategies for the treatment of patients with established venous thrombosis.

Unfractionated heparin is the commonest treatment for established venous thromboembolism. While this treatment undoubtedly reduces mortality and morbidity there are problems associated with its use. It does not always prevent thrombus propagation or embolisation, the low bioavailability results in a frequent failure to achieve therapeutic heparin levels in vivo and the variable sensitivity of the partial thromboplastin time to the heparin effect may result in inappropriate heparin dosage. The low-molecular-weight heparins have high predictable bioavailability and can be administered as weight-calculated fixed-dose regimens for the treatment of established venous thromboembolism. While statistically significant clinical results are awaited, there is increasing evidence for the superior benefit-risk ratios for these agents compared to unfractionated heparin. In routine practice, the frequent failure to achieve a therapeutic intensity of anticoagulation is currently the main reason for adopting low-molecular-weight heparins for first-line treatment of venous thromboembolism. Cost analysis studies based on total health care costs may support the use of these drugs, because savings from the abolishment of laboratory monitoring, improved clinical outcome and shorter inpatient stay may prove treatment with low-molecular weight heparin to be more cost-effective than treatment with unfractionated heparin.