Using anticoagulants is a bit like walking a tightrope. If the dose is too high, there is a danger of hemorrhage. If the dose is too low, there is risk of a deadly blood clot. For years, warfarin, originally sold under the brand name Coumadin, was the primary blood thinner doctors used to treat atrial fibrillation. This irregular heart rhythm can allow a blood clot to form in the heart and be transported to the brain where it could cause a stroke. Preventing clots can prevent strokes.
In recent years a number of new anticoagulants have entered the market including Pradaxa, Eliquis and Xarelto. A meta-analysis compared these newcomers to warfarin and found they were 20 percent better at preventing stroke. Unfortunately, the new blood thinners were also more likely to cause serious gastrointestinal bleeding. Despite the new analysis, an editorial accompanying the research in The Lancet admitted it is still very difficult for doctors to decide which anticoagulant might be best.
[Lancet, online Dec. 4, 2013]