Pharmacotherapy Newsletter

Volume 1, Issue 26, 07/13/2009

Question

What is the mechanism by which the low-molecular weight heparins (LMWH; dalteparin, enoxaparin, tinzaparin) cause less heparin induced thrombocytopenia (HIT) than traditional unfractionated heparin?

Answer

This is part 3 of a 4 part series related to heparin induced thrombocytopenia (HIT).  In part 1 of this series the mechanism of action by which heparin related molecules caused reductions in platelet counts was described in detail.¹  Part 2 addressed the different clinical characteristics for the different types of thrombocytopenia related to heparin use.²  The last two issues in this series will look at some of the factors that increase the risk for developing HIT.  The first of these will address the differences in the incidence of HIT among the different heparin related medications, which mainly include traditional unfractionated heparin (UFH) and the low-molecular weight heparins (LMWH; dalteparin, enoxaparin, and tinzaparin).