What are the differences between heparin and LMWHs?
The reduced affinity for proteins and cells explains the anticoagulant, pharmacokinetic, and other biological differences between heparin and LMWHs. Compared with heparin, LMWHs have reduced ability to inactivate thrombin because the smaller fragments cannot bind simultaneously to AT and thrombin. Reduced binding to plasma proteins other than AT is responsible for the more predictable dose-response relationship of LMWHs. Decreased binding to macrophages and endothelial cells explains the longer plasma half-life of LMWH relative to UFH, whereas reduced binding to platelets and PF4 explains the lower incidence of HIT. Finally, the decreased binding of LMWH to osteoblasts results in less activation of osteoclasts and less bone loss.