When oral anticoagulants are given with heparin, additional anticoagulant effects occur. The major side effect associated with heparin is hemorrhage thrombocytopenia (reduced number of circulating platelets) and hypersensitivity reactions also may occur. The drug’s action is terminated by metabolism in the liver and excretion by the kidneys. Heparin is not bound to plasma proteins, it is not secreted into breast milk, and it does not cross the placenta. Because it is not well absorbed from the gastrointestinal tract, heparin is given intravenously to inhibit coagulation immediately, or it is given subcutaneously. Heparin, used primarily in hospitalized patients, is a mixture of mucopolysaccharides that promote the activity of antithrombin III, a blood plasma protein that inactivates thrombin (an enzyme that promotes clotting). Anticoagulants are also used in drawing and storing blood.Īnticoagulants generally are of two types: heparin, which is given by injection, and derivatives of coumarin or indandione, which are administered orally. Conditions commonly treated with anticoagulants include deep-vein thrombosis, in which clots form in so-called deep veins, such as those of the legs pulmonary embolism, in which a clot obstructs the pulmonary artery or one of its branches coronary thrombosis, in which a clot obstructs a coronary artery in the heart and disseminated intravascular coagulation, a systemic activation of the coagulation system that leads to the consumption of coagulation factors and hemorrhage. Such drugs are often used to prevent the formation of blood clots (thrombi) in the veins or arteries or the enlargement of a clot that is circulating in the bloodstream. Anticoagulants achieve their effect by suppressing the synthesis or function of various clotting factors that are normally present in the blood.

Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Īnticoagulant, any drug that, when added to blood, prevents it from clotting.

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