Warfarin Institute of America
DEDICATED TO YOUR HEALTH SINCE 2000
WHY DO SOME PEOPLE TAKE BOTH WARFARIN (Coumadin, Jantoven) AND ASPIRIN?
There are two blood clotting systems. One involves the blood cells called platelets. These are actually little balls which roll around in the blood. Ordinarily, they roll over each other and the other blood cells. As you can imagine, it is very hard to build a stack of balls. But when they come to an area where a clot is needed, they grow little braces that are like legs. These legs allow them to stick together and form a stack.
What causes platelets to start clots? Usually it is something in an artery. Blood in an artery is under high pressure because it has only recently been pumped out of the heart. When there is something plugging an artery (usually cholesterol) this is like putting your thumb over a garden hose. (The pressure increases more and there are high shear forces on the platelets.)
Aspirin works by preventing the platelets from growing legs. So, aspirin is the best choice for preventing clots which will start in arteries.
The second clotting system involves thrombin. Think of thrombin as being like string. It forms a web and captures platelets to help form a clot.
What causes thrombin to start clots. This usually happens in veins where the blood flow is under lower pressure and moving more slowly than in the arteries. Think of an eddy current in a stream as an example of stagnation. In the blood, the swirling action can lead to thrombin forming a clot.
Warfarin (Coumadin, Jantoven) is the choice when the clot is due to stagnation. The blood flow around a mechanical heart valve is not quite the same as that around a natural valve, so there is likely to be some stagnation. Also, mitral valves are more prone to stagnation that aortic valves because the blood is usually flowing at lesser pressure.
The main problem with aspirin is that it tends to erode the lining of the stomach. This can cause bleeding. When warfarin (Coumadin, Jantoven) is slowing the clotting time, this could lead to a bad situation. But, a small dose of aspirin such as 325 mg per day or less is unlikely to cause this erosion and therefore little harm.
A study by Rothenberg et al found the combination to be beneficial when the person is at low to moderate risk for bleeding.
However, a study by Dentali et al. found almost the opposite. They did a meta-analysis of ten studies using both drugs involving 4180 patients. The risk for a clot in an artery was lower in patients receiving combined aspirin-oral anticoagulation therapy (OAC) (there may have been some drugs that were not warfarin, but similar to it in the studies) compared with OAC therapy alone. However, these benefits were limited to patients with a mechanical heart valve.
There was no difference in the risk for clots in arteries with these treatments in patients with atrial fibrillation or coronary artery disease . There was no difference in all-cause mortality with either treatment. The risk for major bleeding was higher in patients receiving aspirin-OAC therapy compared with OAC therapy alone.
The authors question the current practice of using combined aspirin-OAC therapy except in patients with a mechanical heart valve, given the questionable benefits in reducing clotting events and the increased risk of major bleeding
References:
Rothenberg et al. Ann Intern Med. 2005 Aug 16;143(4):241-50.
Dentali F et al. Arch Intern Med. 2007;167:117-124.
The next question that usually arises is why do the doses of aspirin vary so much? For a discussion of that, see aspirin-platelets
SEE A CATALOG OF PUBLICATIONS AVAILABLE FROM LODWICK CREATIONS, LLC.
LEARN HOW YOU CAN BECOME LISTED ON THE HONOR ROLL OF SUPPORTERS AND TAKE ADVANTAGE OF THE BENEFITS
REQUEST A MEDICATION CONSULTATION
© 2002 - 2007 Lodwick Creations, LLC
Contact Mr. Lodwick at allodwick@earthlink.net
Last update June 14, 2007