Low molecular weight heparin

Background

• A 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.

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.
• 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

• Deep venous thrombosis
• Pulmonary embolism
• Non ST-Elevation Myocardial Infarction (NSTEMI)
• ST-segment elevation myocardial infarction (STEMI)
• Stroke (main)

See Also

• Coagulopathy (main)
• Unfractionated heparin

References

Authors

Ross Donaldson