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Acta Phlebologica 2007 August;8(2):93-104

Copyright © 2007 EDIZIONI MINERVA MEDICA

language: English

Low-Molecular-Weight-Heparins: an update

Antignani P. L. ¹, Goffredo C. ², Lassandro Pepe L. ², Allegra C. ¹

¹ Department of Angiology San Giovanni Hospital, Rome, Italy 2 Department of Cardiovascular Science “Campus Biomedico” University, Rome, Italy

Unfractionated Heparin and Low Molecular Weight Heparins (LMWHs) represent the mainstay of agents available for the management of venous and arterial thrombosis. LMWHs represent the agents of choice for the prevention and treatment of VTE because they have improved pharmacological and pharmacokinetic advantages. LMWHs are derived from UFH by chemical or enzymatic depolymerization; they have a mean molecular weight of 4,000 to 5,000 dalton. The main kind of LMWHs are dalteparin, enoxaparin, nadroparin, certoparin and they can be administered in either the in-hospital or out-of-hospital setting because they can be administered subcutaneously without the need for laboratory monitoring, with better bioavailability. less platelet activation. Several randomized trials have suggested that patients with symptomatic pulmonary embolism or asymptomatic pulmonary embolism, symptomatic deep venous thrombosis can be treated with low-molecular-weight heparin instead of unfractionated heparin. Compared with unfractionated heparin, low molecular weight heparin has a more predictable dose-response relationship (which obviates the need for laboratory monitoring), has a longer half-life (which allows once-daily or twice-daily administration), and confers a lower risk for immune-mediated thrombocytopenia or osteoporosis. This is partly due to more targeted action: unfractionated heparin acts on both thrombin and factor Xa about equally, whereas low molecular weight heparin is more active against factor Xa. The low molecular weight heparins are, however, different, and trials for one cannot be extrapolated to another. The introduction of low molecular weight heparin has advanced antithrombotic therapy by providing effective anticoagulation without the need for routine monitoring or adjustments, although it can be monitored through an anti-Xa effect. It also allows patients with uncomplicated deep vein thrombosis to be treated in the community, thus saving an average of 4 or 5 days of admission per patient. Low molecular weight heparin has been shown to be more effective than vitamin K antagonists (almost all being warfarin) in preventing deep vein thrombosis after major orthopaedic surgery, with no significant difference in rates of bleeding. The current standard of care is to administer weight-adjusted LMWH heparin once daily for 5-7 days as initial treatment following by oral anticoagulant for three or six months or longer: it depends on thrombosis cause. Heparin can be discontinued after 5-7 days, as long as the ratio is stable and is 2.·0 or greater.Once-daily low-molecular weight heparin at a dose of 150-200 U/kg antifactor Xa is as effective and safe as twice-daily 100 U/kg antifactor Xa. Recent evidence suggests that they may be superior for thrombosis in patients with malignant disease, and they can prolong survival in patients with advanced malignant disease.