Aspirin Vs. Coumadin for Blood Thinning

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Both aspirin and Coumadin, the brand name for the drug warfarin, thin blood and help prevent blood clots. Your doctor may prescribe one of these medications if she believes you're at a risk for blood clots or strokes. Stroke is the third leading cause of death in the United States, according to 2011 information from the National Institute of Neurological Disorders and Stroke. Both drugs can be effective and whether you take one or the other, depends on several factors.


Aspirin thins the blood by acting on the platelets, keeping them from sticking together. Warfarin reduces the amount of a protein in the blood, which promotes clotting. Some people may respond better to one treatment than the other, but a 7-year study known as the Warfarin versus Aspirin Recurrent Stroke Study, or WARSS, indicates that for most people, the difference of the effect of the two drugs is slight, notes the National Institute of Neurological Disorders and Stroke.


The Warfarin versus Aspirin Recurrent Stroke Study was published in the November 15, 2001 issue of "The New England Journal of Medicine." The study followed 2,206 patients from 48 different care centers for 7 years. During that time, researchers tracked the incidence of recurrence of stroke in patients taking either warfarin or aspirin. Patients with atrial fibrillation were excluded from this study. During the study, both participants who took aspirin and those who took warfarin suffered about the same incidence of stroke. Older patients had a greater incidence of stroke overall. Patients on aspirin therapy took 325 mg of aspirin daily, while those on warfarin took the dose calculated by their physicians.

Lowering Your Stroke Risk

WARSS looked at patients who are previously suffered strokes. Having a stroke once increases your chances of having a second stroke, but taking aspirin regularly may also reduce your risk of having a first stroke by about 25 percent, according to the National Institute of Neurological Disorders and Stroke. Controlling your blood pressure, blood sugar and cholesterol will also reduce your risk of stroke. The U.S. Preventative Services Task Force recommends men between the ages of 45 and 79 and women ages 55 to 75 should take as little as 75 mg of aspirin daily to decrease their stroke risk.

Atrial Fibrillation

The one area where warfarin shows a clear advantage over aspirin was for patients who suffered from atrial fibrillation. This condition, characterized by an irregular heart rhythm, can produce blood clots from the heart that can cause stroke or heart attack. A study in published in 2005 in the "Texas Heart Institute Journal" indicates that warfarin reduced the rate of recurrent stroke in atrial fibrillation patients by 45 to 52 percent, compared to a reduction rate of only 22 percent for aspirin. Atrial fibrillation causes about 15 percent of strokes, according to the National Institute of Neurological Disorders and Stroke.


Coumadin increases the risk of hemorrhage in patients. Patients who take Coumadin need regular blood tests to monitor levels in the blood. Coumadin is available only be prescription, which is an added expense. While aspirin is less likely to cause hemorrhage, you may bruise more easily while on aspirin. Aspirin can also irritate the stomach and may lead to ulcers. Some people are allergic to aspirin and cannot take it. For them, Coumadin and other blood thinners may be the only choice.