2.1. Unfractionated heparin

Unfractionated heparin (UFH) binds antithrombin—a physiological inhibitor of coagulation and accelerates its inhibitory action against coagulation factors II and X and in minor degrees also factors IX, XI and XII [2, 3]. UFH is active in a parenteral form only and therefore administered by intravenous (i.v.) infusion [2]. It is used for the treatment of acute thromboembolic events. One of the major disadvantages of UFH is its binding to plasma proteins and endothelial cells making its anticoagulant effect unpredictable [2, 3]. Treatment with UFH must, therefore, be regularly monitored with activated partial thromboplastin time (APTT). Due to different sensitivities of APTT reagents the therapeutic APTT range must be determined by each laboratory and must correspond to heparin anti-factor Xa activity between 0.3 and 0.7 IU/mL [4–6]. Treatment is initiated with UFH bolus of 80 U/kg i.v. and continued with continuous infusion of 18 U/kg body mass/h [7]. Dosage must be adjusted according to the APTT result. At the beginning of treatment, laboratory monitoring is needed several times a day, the first one 6 h after UFH initiation. The two most important non-hemorrhagic side effects of UFH treatment are osteoporosis and thrombocytopenia [2].
