Low molecular weight heparin
- Class of anticoagulant medications.
- Defined as heparin salts having an average molecular weight of less than 8000 Dalton
- LMWHs inhibit the coagulation process through binding to antithrombin which in turn inhibits activated factor X.
- LMWH therapy is monitored by the anti-factor Xa assay (measures anti-factor Xa activity).
- Cannot be acceptably measured using the partial thromboplastin time (PTT) or activated clotting time (ACT) tests.
|LMWH||Average molecular weight||Ratio anti-Xa/anti-IIa activity|
Clinical Differences from Unfractionated heparin
- Less frequent subcutaneous dosing
- Once or twice daily subcutaneous injection for treatment of venous thromboembolism and in unstable angina instead of intravenous infusion of high dose heparin.
- No need for monitoring of the aPTT coagulation parameter as required for high dose heparin.
- Possibly a smaller risk of bleeding
- Smaller risk of osteoporosis in long-term use.
- Smaller risk of heparin-induced thrombocytopenia, a potential side effect of heparin.
- The anticoagulant effects of heparin are typically reversible with protamine sulfate, while protamine's effect on LMWH is limited.
- Garcia DA, Baglin TP, Weitz JI, et al. (2012). "Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines"