anticoagulant

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anticoagulant

(ăn'tēkōăg`yələnt), any of several substances that inhibit blood clot formation (see blood clottingblood clotting,
process by which the blood coagulates to form solid masses, or clots. In minor injuries, small oval bodies called platelets, or thrombocytes, tend to collect and form plugs in blood vessel openings.
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). Some anticoagulants, such as the coumarin derivatives bishydroxycoumarin (Dicumarol) and warfarin (Coumadin) inhibit synthesis of prothrombin, a clot-forming substance, and other clotting factors. The coumarin derivatives compete with vitamin K, which is a necessary substance in prothrombin formation (see vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
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). They are only effective after the body's existing supply of prothrombin is depleted. Another anticoagulant, heparin, is a polysaccharide (see carbohydratecarbohydrate,
any member of a large class of chemical compounds that includes sugars, starches, cellulose, and related compounds. These compounds are produced naturally by green plants from carbon dioxide and water (see photosynthesis).
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) found naturally in many cells. It acts in several ways: by preventing prothrombin formation; by preventing formation of fibrin, another clotting substance; and by decreasing the availability of a third clotting factor, thrombin. 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.
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anticoagulant

[¦an·tē‚kō′ag·yə·lənt]
(pharmacology)
An agent, such as sodium citrate, that prevents coagulation of a colloid, especially blood.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

anticoagulant

1. acting to prevent or impair coagulation, esp of blood
2. an agent, such as warfarin, that prevents or impairs coagulation
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
We demonstrate that after oral ingestion, MK-7 is more effective in both catalyzing osteocalcin carboxylation in bone and counteracting coumarin anticoagulants in the liver.
Of course, on the negative side, this increased tissue utilization of MK-7 can pose problems for patients using coumarin anticoagulants. One reason is that, unlike osteocalcin in bone, in the average healthy population clotting factors in the liver are fully carboxylated: "The vitamin K-dependent clotting factors are all produced in the liver and, in contrast to osteocalcin, they are all fully carboxylated in the healthy population."
The product ion chromatograms and corresponding spectra obtained from an extracted plasma sample of a patient with an increased prothrombin time, who repeatedly denied taking coumarin anticoagulants, are depicted in Fig.