Harvard Heart Letter

Ask the doctor: Do I need to take precautions if I stop taking warfarin before a colonoscopy?

Q. I am due to have a colonoscopy. My cardiologist told me that I will need to stop taking Coumadin, which I take for atrial fibrillation, a few days before the procedure and get some injections. Is that really necessary?

A. Warfarin (Coumadin, Jantoven, generic) is an important medication for people with atrial fibrillation because it helps prevent stroke-causing blood clots from forming inside the heart. The concern with colonoscopy is that the doctor might need to take a biopsy or remove a polyp during the procedure, and being on warfarin increases the risk of bleeding.

There is currently no standard procedure for stopping warfarin before a colonoscopy. Most doctors are guided by a patient's chances of developing a blood clot. If you are at low risk, you should be able to safely stop warfarin for a few days before having your colonoscopy. If you are at high risk (for example, if you have had a blood clot or stroke while off warfarin for only a few days), you will need something to replace warfarin. The most commonly used bridging therapy is injections of a short-acting low-molecular-weight heparin like enoxaparin (Lovenox) or dalteparin (Fragmin). Like warfarin, these make blood less likely to form clots in the bloodstream. The last injection is usually given 24 hours before the colonoscopy. By the time of the procedure, its blood-thinning effect has worn off.

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