Anticoagulant, << `an` tee koh AG yuh luhnt, >> is a chemical substance used to prevent the normal coagulation (clotting) of blood. The chief types are (1) drugs that slow clotting in a person’s bloodstream and (2) substances that prevent the clotting of blood in a test tube.
Anticoagulant drugs are administered to treat and prevent blood clots. They often are used in the treatment of thrombophlebitis, the formation of a clot in a damaged vein (see Phlebitis ). When a vein is damaged, a series of reactions changes an inactive blood chemical called prothrombin into thrombin. Thrombin, in turn, helps cause the formation of fibrin, the protein that makes up the most important part of a clot. Anticoagulant drugs reduce the speed of one of these steps. For example, dicoumarol slows the conversion of prothrombin into thrombin.
Certain anticoagulants are added to blood stored for transfusions and to blood samples used for laboratory tests. These anticoagulants work by joining with calcium ions in the blood. Free calcium ions must be in the blood for clotting to occur.
