Blood Thinner

What are Blood Thinners?

Blood thinners, also known as anticoagulants or anticoagulant agents, are used to prevent the formation of blood clots. Anticoagulants do not actually thin the blood; they help prevent it from clotting. Medicinally, blood thinners are basically used in two different ways. One method is for treating thrombosis, or more generally thrombotic disorders. This involves treating the patient with a "blood thinner" medication. The other method is for treating medical equipment such as donated blood bags (to prevent clotting while in storage), test tubes, or kidney dialysis equipment. A non-medical application includes the use of blood thinners as a pesticide, normally as a rat poison.

How Blood Thinners Work

Coagulation or the clotting of blood is actually a very complex chemical event that includes several different chemical reactions that occur due to the presence of enzymes (proteins that speed up a chemical reaction). The the process of clotting blood requires several ingredients including Vitamin K, Calcium, phospholipids, thrombin, many different proteins and enzymes and fibrinogen. For the most part, each of these ingredients (and many more) plays a specific role in the creation of blood clots.

Types of Blood Thinners

Blood thinners are prescribed to treat a variety of thrombotic disorders, and are often used as a prophylactic (preventive) for these disorders which may include, stroke, myocardial infarctions (MIs), deep vein thrombosis (DVT), and pulmonary embolisms. Blood thinners can also be categorized into groups based on how they function.

The medicinal anticoagulants that are taken orally fall into a class of pharmaceuticals know as Vitamin K antagonists. Vitamin K is used in several different steps of the blood clotting process. A specific Vitamin K enzyme reverts Vitamin K back to its active form so that it may be used. Vitamin K antagonists create a deficiency of reduced Vitamin K by blocking the action of the enzyme, which in turn inhibits the completion of blood clotting process.

Vitamin K antagonists include acenocoumarol (brand names Sintrom and Sinthrome), phenindione, phenprocoumon (Marcoumar, Marcumar, and Falithrom), and dicoumarol as well as the coumadin deriviative Warfarin (Coumadin, Jantoven, Marevan, Lawarin, and Waran). One important note about these types of blood thinners, they do not work right away. They generally require a 48 to 72 hour period before they begin working fully and are often given with injection-type antithrombin drugs.

Antithrombin drugs include heparin, enoxaparin, dalteparin, and tinzaparin. These medications are delivered by injection either subdermally or subcutaneously (intramuscular injections are avoided to prevent hematomas) and begin working immediately. The medications bind to the enzyme inhibitor antithrombin, causing it to be active. The activated antithrombin then inactivates thrombin and other chemicals in the coagulation cascade, notably one called factor Xa.

Another category of anticoagulants are direct thrombin inhibitors. Their mechanism includes direct inhibition or inactivation of thrombin. These drugs are normally given by injection and may include, argatroban, bivalirudin (Angiomax), dabigatran (Pradax or Pradaxa), and lepirudin (Refludan).

Blood thinners used to treat medical equipment are usually calcium ion binders. Binding calcium ions prevents the coagulation proteins in the coagulation cascade from using them. These include EDTA, oxalate, and citrate. Some brands of blood sampling test tubes have color coded tops based on which chemical is used to prevent clotting.

Finally, brodifacoum, a blood thinner that is incredibly potent and has a long half life is used as a pesticide. It is used mostly to exterminate rats and other rodents but has also worked for opossums.

As a side note, clopidrogrel sulfate (Plavix, Clopilet, Ceruvin, and Clavix) is also commonly referred to as a blood thinner, however it does not work by any of the mechanisms mentioned above. Clopidrogel is an inhibitor of Adenosphine Diphosphate (ADP) induced platelet aggregation. Platelets or thrombocytes clump together using fibrinogen and other agents to assist in forming blood clots.

Side Effects from Blood Thinners

Like most medicines, there are several adverse effects that are possible from taking anticoagulants. Some are specific to a particular class of anticoagulant. However, the most common side effects from taking anticoagulants are:

• Hemorrhage;
• Nausea
• Vomiting;
• Loss of appetite;
• Stomach/abdominal cramps; and,
• In the case of heparin usage for example, heparin induced-thrombocytopenia or HIT.