AH Yes, I see that clarification is needed here.
Aspirin (as an anti-platelet) DOES affect CLOTTING but DOES NOT affect INR (which was the original question).
It is known that Antacids can affect absorption of Coumadin if taken within 2 hours of each other therefore a cautionary note is usually included stating that Coumadin should NOT be taken within 2 hours of taking an Antacid (which probably also applies to proton pump inhibitors such as Prilosec / Omeprazole or Nexium, etc.)
FWIW, I take both of the above, but take my Coumadin at night and the others in the morning.
Here is what I found on
http://www.drugdigest.org/DD/Interaction/
WARFARIN SODIUM (in Coumadin) may interact with OMEPRAZOLE (in Omeprazole capsules)
Omeprazole may block the breakdown of warfarin by the liver. If this happens, blood levels of warfarin could be increased and this could increase its anticoagulant effect. Warfarin is generally used to prevent your blood from "coagulating" or forming blood clots. When omeprazole and warfarin are used at the same time, your blood may be much less likely to clot and this may increase the risk of excessive bleeding. If these drugs are taken together, your doctor may want to monitor you closely when therapy with omeprazole is either started or stopped. Blood tests can be used to make sure that you are getting the right amount of warfarin. If you are experiencing problems, it may be necessary to adjust the dose of warfarin. You may want to ask your healthcare provider about this potential interaction if you think you are having problems.
This interaction is poorly documented and is considered moderate in severity.
Last Updated: March 2005
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ASPIRIN may interact with WARFARIN SODIUM (in Coumadin)
Blood clotting normally occurs in response to a cut or other types of injuries to protect the body from excessive bleeding. Platelets, a type of cell found in the blood, are involved in helping the blood to clot when it is needed. Aspirin may interfere with the platelets' ability to work properly, particularly when used in doses of more than 3000mg per day. Warfarin is generally used to prevent your blood from "coagulating" or forming blood clots. When aspirin and warfarin are used at the same time, your blood may be much less likely to clot and this may increase the risk of excessive bleeding. If it is necessary to use aspirin while you are taking warfarin, your doctor may want to monitor you closely for signs of a bleeding disorder. Blood tests can be used to make sure that you are getting the right amount of warfarin. If you are experiencing problems, it may be necessary to adjust the dose of warfarin. Ask your healthcare provider about these drugs and this potential interaction as soon as possible.
This interaction is well-documented and is considered major in severity.
Last Updated: March 2005
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OMEPRAZOLE (in Omeprazole capsules) may interact with ASPIRIN
Enteric-coated aspirin generally causes less stomach irritation than regular aspirin because it does not dissolve until it reaches the intestine. Decreasing the acid content in the stomach may cause the enteric coating to dissolve and release the aspirin directly into the stomach. This could increase the risk for side effects such as stomach irritation and bleeding, especially in those people who have an ulcer. Omeprazole decreases the acid content in the stomach. If possible, avoid using omeprazole and enteric-coated aspirin at the same time. Ask your doctor or pharmacist about alternatives to enteric-coated aspirin to provide relief from pain or to reduce a fever. You may want to ask your healthcare provider about this potential interaction if you think you are having problems.
This interaction is poorly documented and is considered minor in severity.
Last Updated: December 2003
