Coagulation
Anticoagulants and procoagulants
Heparin - low molecular weight
Author: Jeremy C. Parsons, M.D.
Last author update: 1 June 2012
Last staff update: 28 September 2020
Copyright: 2002-2023, PathologyOutlines.com, Inc.
PubMed Search: Heparin [title] AND low molecular weight[title]
Table of Contents
Definition / general | Diagrams / tables | Clinical features | Laboratory | Additional referencesCite this page: Parsons JC. Heparin - low molecular weight. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationheparinLMW.html. Accessed June 3rd, 2023.
Definition / general
- Can be used instead of standard heparin for many patients, with similar efficacy and safety
- Produced by breaking heparin into shorter polysaccharide chains
- Molecular weight is approximately 5,000 daltons
Diagrams / tables
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Function of LMWH
Clinical features
- Less likely to bind to acute phase reactant proteins, platelets, platelet factor 4, macrophages and other sites, due to its shorter length
- Has more predictable anticoagulant effect than standard heparin, less need for laboratory monitoring, lower incident of heparin induced thrombocytopenia, greater bioavailability
- Longer half life than standard heparin (4 vs. 1.5 hours), which is prolonged in renal failure
- Inhibits factor Xa by 2 to 4x more than factor IIa, so does not substantially prolong PT and PTT
- Unlike regular heparin, does not as readily inhibit thrombin or factor IXa (this also contributes to a lower number of bleeding side effects)
Laboratory
- Typically do not monitor except for periodic platelet counts
- Indications for monitoring include pregnancy, renal failure, obesity, prolonged use, infants and children, patients at high risk for bleeding / thrombosis
- Monitor by measuring anti-factor Xa activity, drawn 4 hours after injection
- Typical therapeutic range is 0.6 to 1.0 U/ml for twice a day dosing, higher for once a day dosing, 1.0 to 2.0 U/ml for prophylactic dosing
- Effects are reversed with protamine sulfate
Additional references
