Heparins

This section compares anticoagulation using unfractionated heparin, low molecular weight heparin and heparinoids

Unfractionated heparin (UFH) has been used for the prevention and treatment of thrombosis for several decades
Heparin is mainly obtained from porcine intestine1
UFH is a mixture of sulphated glycosaminoglycans of variable lengths and molecular weights
Anticoagulant effects and pharmacological properties vary with the size of the molecules
Administered parenterally
UFH has limited bioavailability because it binds to plasma proteins, platelets (platelet factor 4), macrophages, and endothelial cells, resulting in a highly variable anticoagulant response2
UFH inactivates several coagulation enzymes, including Factors IIa (thrombin), Xa, IXa, XIa, and XIIa, by binding to the cofactor AT2

Low molecular weight heparins (LMWHs) are derived from UFH by depolymerization1
Each LMWH product has a specific molecular weight distribution that determines its anticoagulant activity and duration of action, so one product cannot always be substituted for another
LMWHs in current use globally include enoxaparin, dalteparin, nadroparin, tinzaparin, certoparin, reviparin, ardeparin, parnaparin and bemiparin3
Administered subcutaneously for VTE prevention
Like UFH, LMWHs inactivate several coagulation enzymes by binding to AT50 but have a lower affinity for binding to proteins other than AT and are, therefore, associated with a predictable dose–response and have fewer non-haemorrhagic side-effects4
Because of several clinical advantages, LMWHs have gradually replaced UFH for most indications

Danaparoid, available in several countries, is classified as a heparinoid
It is composed of sulphated glycosaminoglycans and can be used as an alternative to heparin in patients suffering from an antibody-mediated form of heparin-induced thrombocytopenia2

Haines ST, Racine E, Zeolla M. Venous thromboembolism. In: DiPiro J, Talbert R, Yee G et al (eds). Pharmacotherapy: a pathophysiologic approach. 5th edn. New York, NY, USA: McGraw-Hill Companies, Inc.; 2002. p. 337–373. Return to content
Hirsh J, Bauer KA, Donati MB et al. Parenteral anticoagulants: American College of Chest Physicians evidence-based clinical practice guidelines (8th Edition). Chest 2008;133:141S–159S. Return to content
Bick RL, Frenkel EP, Walenga J et al. Unfractionated heparin, low molecular weight heparins, and pentasaccharide: basic mechanism of actions, pharmacology, and clinical use. Hematol Oncol Clin North Am 2005;19:1–51, v. Return to content
Garcia DA, Baglin TP, Weitz JI, Samama MM. Parenteral anticoagulants: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2012;141:e24S–e43S. Return to content

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