Pharmacotherapy Newsletter

Volume 2, Issue 1, 01/05/2010

Question

Why is fondaparinux (Arixtra) an alternative anticoagulant that can be used in patients with heparin induced thrombocytopenia (HIT) but not low-molecular weight heparins (LMWH)?

Answer

The use of anticoagulants, such as unfractionated heparin (UFH) and low-molecular weight heparin (LMWH) have significantly improved patient oriented outcomes for medical conditions related to thrombotic events.  However, they are also known to cause clinically relevant side effects, or adverse drug events, such as bleeding (including hemorrhagic stroke, gastrointestinal bleeding, osteoporosis (long-term use)), priapism, and hyperkalemia (from inhibition of aldosterone synthesis).(1-3)  Paradoxically, their use can also put patients at risk for fatal thrombosis that can cause such things as deep vein thrombosis (DVT), pulmonary embolism (PE), myocardial infarction (MI), thrombotic stroke, cerebral vein thrombosis and disseminate intravascular coagulation.(4,5)  This condition is called heparin induced thrombocytopenia (HIT). 

There are number of risk factors associated with increasing the chance for a patient to develop HIT, one of which is the type of anticoagulant used.  For example, it is known that...

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