World Library  
Flag as Inappropriate
Email this Article

Anticoagulants

Article Id: WHEBN0000511236
Reproduction Date:

Title: Anticoagulants  
Author: World Heritage Encyclopedia
Language: English
Subject: ICD-10 Chapter XX: External causes of morbidity and mortality
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Anticoagulants

An anticoagulant is a substance that prevents coagulation (clotting) of blood. Such substances occur naturally in leeches and blood-sucking insects. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some anticoagulants are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis equipment. Natural anticoagulants: Heparin, Anti-thrombin III, Fibrin, Anti-thromboplastin, Heparan Sulphate, Protein C, Protein S etc.

As medications

Anticoagulants reduce blood clotting. This prevents deep vein thrombosis, pulmonary embolism, myocardial infarction and stroke.

Coumarins (vitamin K antagonists)

Further information: Vitamin K antagonist

These oral anticoagulants are derived from coumarin, which is found in many plants. A prominent member of this class is warfarin (Coumadin). It takes at least 48 to 72 hours for the anticoagulant effect to develop. Where an immediate effect is required, heparin must be given concomitantly. These anticoagulants are used to treat patients with deep-vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation (AF), and mechanical prosthetic heart valves.

Adverse effects

Patients aged 80 years or more may be especially susceptible to bleeding complications, with a rate of 13 bleeds per 100 person-years.[1] These oral anticoagulants are used widely as poisons for mammalian pests, especially rodents. (For details, see rodenticide and warfarin.) Depletion of vitamin K by Coumadin therapy increases risk of arterial calcification and heart valve calcification, especially if too much vitamin D is present.[2]

Available agents

Heparin and derivative substances

Heparin is a biological substance, usually made from pig intestines. It works by activating antithrombin III, which blocks thrombin from clotting blood. Heparin can be used in vivo (by injection), and also in vitro to prevent blood or plasma clotting in or on medical devices. Vacutainer brand test tubes containing heparin are usually colored green.

Major pharmaceutical heparin recall due to contamination

In March 2008, major recalls of heparin were announced by pharmaceutical companies due to a suspected and unknown contamination of the raw heparin stock imported from China.[4][5] The contaminant was later found to be a compound called oversulfated chondroitin sulfate.[6] The US Food and Drug Administration was quoted as stating at least 19 deaths were believed linked to a raw heparin ingredient imported from the People's Republic of China, and they had also received 785 reports of serious injuries associated with the drug’s use. According to the New York Times: 'Problems with heparin reported to the agency include difficulty breathing, nausea, vomiting, excessive sweating and rapidly falling blood pressure that in some cases led to life-threatening shock'.

Low molecular weight heparin

Low molecular weight heparin, a more highly processed product, is useful as it does not require monitoring of the APTT coagulation parameter (it has more predictable plasma levels) and has fewer side effects.

Synthetic pentasaccharide inhibitors of factor Xa

  • Fondaparinux is a synthetic sugar composed of the five sugars (pentasaccharide) in heparin that bind to antithrombin. It is a smaller molecule than low molecular weight heparin.
  • Idraparinux

Direct factor Xa inhibitors

Main article: Direct Xa inhibitor

Drugs such as rivaroxaban and apixaban work by inhibiting factor Xa directly (unlike the heparins and fondaparinux, which work via antithrombin activation).

Direct thrombin inhibitors

Another type of anticoagulant is the atrial fibrillation.

Antithrombin protein therapeutics

The antithrombin protein itself is used as a protein therapeutic that can be purified from human plasma[8] or produced recombinantly (for example, Atryn, which is produced in the milk of genetically modified goats.[9][10])

Antithrombin is approved by the FDA as an anticoagulant for the prevention of clots before, during, or after surgery or birthing in patients with hereditary antithrombin deficiency.[8][10]

Other types of anticoagulants

Many other anticoagulants exist, for use in research and development, diagnostics, or as drug candidates.

Food and herbal supplements

Foods and food supplements with blood-thinning effects include nattokinase, lumbrokinase, alfalfa, avocado, beer, bilberry, cat's claw, celery, coenzyme Q10, cranberries, fish oil, garlic, ginger, ginkgo, ginseng, grapefruit, green tea, horse chestnut, licorice, niacin, onion, papaya, pomegranate, red clover, soybean, St. John’s wort, turmeric, wheatgrass, and willow bark.[11] Many herbal supplements have blood-thinning properties, such as danshen and feverfew. Multivitamins that do not interact with clotting are available for patients on anticoagulants.

General indications

Therapeutic uses of anticoagulants include atrial fibrillation, pulmonary embolism, deep vein thrombosis, venous thromboembolism, congestive heart failure, stroke, myocardial infarction, and genetic or acquired hypercoagulability.

Laboratory use

Laboratory instruments, blood transfusion bags, and medical and surgical equipment will get clogged up and become nonoperational if blood is allowed to clot. In addition, test tubes used for laboratory blood tests will have chemicals added to stop blood clotting. Apart from heparin, most of these chemicals work by binding calcium ions, preventing the coagulation proteins from using them.

  • EDTA strongly and irreversibly binds calcium. It is in a powdered form. Full Form of EDTA is Ethyinene Diamine Tetra Acitic Acid. It chelates calcium ion to prevent blood from clotting.
  • Citrate is in liquid form in the tube and is used for coagulation tests, as well as in blood transfusion bags. It binds the calcium, but not as strongly as EDTA. Correct proportion of this anticoagulant to blood is crucial because of the dilution, and it can be reversed with the addition of calcium. It can be in the form of sodium citrate or acid-citrate-dextrose.
  • Oxalate has a mechanism similar to that of citrate. It is the anticoagulant used in fluoride oxalate tubes used to determine glucose and lactate levels.

See also

References

External links

  • Staying Active and Healthy with Blood Thinners by the Agency for Healthcare Research and Quality
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.