Low molecular weight heparin
Background
- 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.[1]
- 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.
Types
| LMWH | Average molecular weight | Ratio anti-Xa/anti-IIa activity |
|---|---|---|
| Bemiparin | 3600 | 8.0 |
| Nadroparin | 4300 | 3.3 |
| Reviparin | 4400 | 4.2 |
| Enoxaparin (Lovenox) | 4500 | 3.9 |
| Parnaparin | 5000 | 2.3 |
| Certoparin | 5400 | 2.4 |
| Dalteparin | 5000 | 2.5 |
| Tinzaparin | 6500 | 1.6 |
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.[2]
- 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.
Indications
References
- 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"
- http://chestjournal.chestpubs.org/content/119/1_suppl/64S.full
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