Low Molecular Weight Heparin (LMWH)


Low molecular weight heparin (LMWH) is an anticoagulant injected subcutaneously or intravenously and acts via activation of antithrombin III which in turn inactivates thrombin and factor Xa to produce its effect.

While similar in mechanism to unfractionated heparin, LMWH is cleared renally, has a much longer half-life and less commonly causes heparin-induced thrombocytopenia (HIT).

Monitoring drug activity is not usually necessary for LMWH unlike unfractionated heparin which requires close monitoring of the activated partial thromboplastin time (aPTT). Measuring factor Xa activity can be done if clinically needed to determine the effect of LMWH.


Enoxaparin (Lovenox), dalteparin (Fragmin), multiple others not commonly used


LMWH is used to treat acute coronary syndromes and venothromboembolism. LMWH is also used for venothromboembolism prophylaxis in hospitalized patients.

Adverse Effects

Bleeding, heparin induced thrombocytopenia (HIT), elevated liver function testing, aldosterone inhibitory effect causing hyperkalemia