There are 2 types of blood thinners, anticoagulants and antiplatelet drugs.
Blood clots can cause problems when they prevent blood from flowing freely, especially to the heart and brain. Sometimes a doctor may not want a patient’s blood to clot as easily and will prescribe a blood thinner.
Heart disease or prior heart attack
Blood vessel disease
Prior stroke or transient ischemic attacks
Being overweight or having metabolic syndrome
Being a smoker
Taking certain other medications
Certain operations, such as angioplasty
Atrial fibrillation (abnormal heart rhythm)
Prior surgery on a heart valve
Congenital (since birth) heart defect
Deep vein thrombosis
The 2 types of blood thinners work in different ways (Figure). Blood-thinning drugs have been used for many years. Newer medications are now available, but they may be more costly or less convenient or have other drawbacks compared with older drugs. Some commonly used anticoagulants are heparin, enoxaparin or other low-molecular-weight heparins, fondaparinux, and warfarin; newer anticoagulants are dabigatran, rivaroxaban, and apixaban. Common antiplatelets include aspirin, aspirin plus extended-release dipyridamole, clopidogrel, prasugrel, and the newer drug cangrelor.
Antiplatelets are usually given orally. Sometimes, the anticoagulant heparin is given continuously through the veins in the hospital. Warfarin is started orally while a patient is receiving intravenous heparin and is continued after the heparin is stopped. Once the INR (international normalized ratio, a test of blood clotting) is stable, heparin is stopped and the patient continues to take warfarin after leaving the hospital. It takes some care to maintain the correct level of warfarin. Patients must keep track of foods they eat that contain vitamin K, especially green leafy vegetables. Patients typically have their blood tested daily, then monthly, based on the INR, which shows how well the warfarin treatment is reducing blood clotting. Some conditions require lifelong treatment with blood thinners.
In some circumstances, enoxaparin or fondaparinux can be used instead of heparin and/or warfarin. Although they require daily injections, they do not require routine INR testing of blood clotting.
If you are prescribed a blood thinner, be sure to tell your doctor about any other medications you take. And if you are taking a blood thinner, you need to be cautious about using over-the-counter medications or herbal (dietary) supplements. Although some new anticoagulants do not interact with vitamin K, their interaction with other substances has not been well studied.
National Library of Medicinewww.nlm.nih.gov/medlineplus/bloodthinners.htmlwww.nlm.nih.gov/medlineplus/bloodclots.html
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Conflict of Interest Disclosures: The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Source: Bonow RO et al. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, PA: Elsevier Sanders; 2012:chap 87.
Correction: This article was corrected for a typo on August 6, 2014.
Topic: Drug Therapy
Deborah Tolmach Sugerman. Blood Thinners. JAMA. 2013;310(23):2579–2580. doi:10.1001/jama.2013.282755