Low Molecular Weight Heparins
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Overview
Low molecular weight heparins (LMWHs) are injectable anticoagulants derived from unfractionated heparin through chemical or enzymatic depolymerization. They are used to prevent and treat deep vein thrombosis, pulmonary embolism, and acute coronary syndromes. Compared to unfractionated heparin, LMWHs have more predictable pharmacokinetics, longer half-lives, and can be administered subcutaneously without routine laboratory monitoring.
How do low molecular weight heparins work?
Low molecular weight heparins bind to antithrombin III (AT-III) via a specific pentasaccharide sequence, potentiating its inhibitory activity. The LMWH-AT complex primarily inactivates Factor Xa, with a much lower ratio of anti-Factor IIa (thrombin) activity compared to unfractionated heparin. This preferential anti-Xa activity (anti-Xa:anti-IIa ratio of approximately 3:1 to 4:1) provides effective anticoagulation with a more predictable dose-response relationship and a lower risk of heparin-induced thrombocytopenia.
Drugs in this class
- Enoxaparin (Lovenox)