Heparins and heparin–induced thrombocytopenia

This chapter discussed the pharmacology and use of the heparins–standard heparin, low molecular weight heparin, and fondaparinux. The complication of heparin–induced thrombocytopenia is also discussed. Heparin functions as an antithrombotic agent by binding antithrombin (AT), promoting inactivation of the active serine proteases involved in blood coagulation (factors IIa, VIIa–TF, IXa, Xa, and XIa). Heparin is a blend of saccharide polymers ranging in molecular weight from 3 to 30,000 Da. A specific pentasaccharide sequence is required for promoting AT activity. This sequence is found in only one–third of the heparin molecules in the heparin currently used. Other polymers found in heparin may have platelet–inhibitory effects or fibrinolytic effects.