The use of heparin is prophylactic. It is used either to prevent thromboembolism (a condition in which a blood clot forms inside a vessel) or used to limit a previous thromboembolism.
Heparin inhibits thrombin. The degree of inhibition is dose-dependent. Low doses of heparin inhibit initial thrombin formation in the coagulation cascade and act to slow down overall thrombin generation. At higher doses, heparin can inhibit thrombin entirely, making blood coagulation impossible. Heparin is a potent anticoagulant. Accurate monitoring is essential. The activated partial thromboplastin time (aPTT), activated clotting time (ACT), and/or anti-Xa assays are used to monitor unfractionated heparin therapy.
