Blood thinners are medications used to prevent blood clots from forming in the circulatory system. If a blood clot forms in a vein or artery, it can travel to the heart, brain or lungs, causing, depending on the clot's location, a heart attack, stroke or pulmonary embolism. People who have irregular heart rhythms (atrial fibrillation) or congenital heart defects, or who have had coronary stents inserted or undergone heart-valve surgery, have a greater likelihood of getting blood clots.
Blood-clotting is a necessary reaction by the body to injury. Clots are formed when platelets, red blood cells, white blood cells and fibrin bind together in clusters at the site of a wound to stop blood loss. Some people, however, are predisposed to forming unnecessary blood clots, and need to take blood thinners to reduce chances that clots will develop.
Types of Blood Thinners
Blood thinners fall into two categories; each affects the blood-clotting process differently. Blood thinners can only prevent clots from forming; they are not capable of breaking up clots that have already formed.
Antiplatelet drugs work to stop platelets from clumping together to from a clot. They are usually taken orally. Antiplatelet drugs include aspirin and various prescription medications. They have few food or drug interactions, but can be problematic for people who have asthma, high blood pressure, liver or kidney disease, or ulcers.
Anticoagulant drugs interrupt the chemical processes involved in blood clotting to extend the time it takes blood clots to form. Heparin and warfarin are two types of anticoagulants; heparin is sometimes started intravenously. Anticoagulant drugs are considered a more aggressive treatment than antiplatelet drugs, and are usually recommended for people at high risk for strokes, or who have atrial fibrillation. In the past few years, the United States Food and Drug Administration has approved a number of new anticoagulants: apixaban, dabigitran and rivaroxaban.
Patients on blood thinners are often subject to monthly blood tests that measure how fast blood clots form. Depending on results, doses may be adjusted.
Risks of Blood Thinners
Bleeding is the most common risk of blood thinners. A patient taking blood thinners must confer with her or his physician before using other medications, including many over-the-counter drugs. Aspirin in particular is known to increase the effect of blood thinners, which puts the patient at a greater risk for excessive bleeding. Other medications, such as nonsteroidal anti-inflammatories, some medicines used to treat colds or stomach upset, and various herbal formulations and vitamins (particularly vitamin K), may be contraindicated, because they, too, can cause bleeding.
Patients on blood thinners are susceptible to internal bleeding, so they should contact their physicians if they fall or bump themselves forcefully.