Anticoagulant agent: A medication used to prevent the formation of blood clots and to maintain open blood vessels. Anticoagulants are called blood "thinners," but they do not thin the blood, they only prevent or reduce clots, or thrombi. Anticoagulants have various uses. Some are used for the prophylaxis (prevention) or the treatment of thromboembolic disorders, such as stroke, heart attack (myocardial infarction) and deep venous thrombosis (DVT). Emboli are clots that break free, travel through the bloodstream, and lodge in a blood vessel, such as a Pulmonary embolism. The anticoagulant drugs used for these clinical purposes include:
- Intravenous heparin -- which acts by inactivating thrombin and several other clotting factors required for a clot to form; there are many newer agents, such as enoxaparin (brand name Lovenox), fondaparinux (brand name Arixtra), and others.
- Oral anticoagulants such as warfarin and dicumarol -- which act by inhibiting the liver's production of vitamin K dependent factors crucial to clotting. Some newer oral agents, rivaroxaban (brand name Xarelto) and dabigatran (brand name Pradaxa)work by inhibiting factor Xa and by directly inhibiting thrombin, respectively.
Anticoagulants are also used to keep laboratory blood specimens from clotting. These agents include not only heparin but also several agents that make calcium ions unavailable to the clotting process and so prevent the formation of clots; these agents include ethylenediaminetetraacetic acid (commonly called EDTA), citrate, oxalate and fluoride.