What is an anticoagulant?
An anticoagulant (an"tih-ko-AG'u-lant) is a drug that helps prevent the clotting (coagulation) of blood. These drugs tend to prevent new clots from forming or an existing clot from enlarging. They don't dissolve a blood clot. Anticoagulants are also given to certain people at risk for forming blood clots, such as those with artificial heart valves or who have atrial fibrillation (A'tre-al fib"rih-LA'shun).

A common type of stroke is caused by a blood clot blocking blood flow to the brain. To prevent such clots, anticoagulants are often prescribed for people with conditions such as atrial fibrillation to prevent a first or recurrent stroke.

Heparin (HEP'ah-rin) and warfarin, a derivative of coumarin (KOO'mah-rin), are some examples of anticoagulants.

Related AHA publications:

• Heart and Stroke Facts
• Your Heart and Anticoagulants brochure    
• "What Are Anticoagulants and Antiplatelet Agents?" printable sheets in Answers By Heart kit

Related AHA Scientific Statements
Anticoagulants