The Columbia Encyclopedia, Sixth Edition. Columbia Encyclopedia World Factbook American Heritage Coll. They are only effective after the body's existing supply of prothrombin is depleted. Heparin is obtained by extracting it from animal tissues. Anticoagulants are used to treat blood clots, which appear especially frequently in veins of the legs and pelvis in bedridden patients.
Therapy helps to reduce the risk of clots reaching the lung, heart, or other organs.
Heparin causes an instantaneous increase in blood-clotting time, and its effect lasts several hours. The Columbia Encyclopedia, Sixth Edition.