Atrial fibrillation is a very common abnormal heart rhythm affecting 3 million Americans. The most dangerous complication of atrial fibrillation is stoke, which can happen when a blood clot forms in the fibrillating heart chambers and travels to the brain.
Blood thinners have been the mainstay of treatment for atrial fibrillation. They reduce the risk of stroke by preventing blood clots. Warfarin (marketed under the brand name Coumadin) is the most effective available oral blood thinner, but taking it is fraught with difficulty. The appropriate dose varies widely between individuals because of genetic differences, and even in the same individual the correct dose varies from one time to another. The only way to dose warfarin correctly is to check blood tests periodically and adjust the dose based on the results. Too much warfarin and the risk of dangerous bleeding increases; too little and the risk of stroke from atrial fibrillation is undiminished. This need for frequent lab monitoring and the many interactions that warfarin has with foods and with other medications make it one of the least convenient and potentially most dangerous medicines in common use. But for atrial fibrillation warfarin is the best we have.
An important study in this week’s New England Journal of Medicine compares a new blood thinner, dabigatran, with warfarin. Over 18,000 patients with atrial fibrillation were randomized to either warfarin or to two different doses of dabigatran. The lower dose of dabigatran was as effective at preventing strokes as warfarin, but was safer, causing fewer incidents of major bleeding. The higher dose of dabigatran was as safe as warfarin (i.e. equal numbers of major bleeding) but prevented more strokes.
That by itself would be encouraging enough, but the major advantage for many patients will be that dabigatran does not require laboratory monitoring and has much fewer interactions with other medications. It is taken twice a day at a fixed dose, making it dramatically simpler than taking warfarin.
Dabigatran should be available in the US in 2010.
Wall Street Journal article: New Blood Thinner Matches Warfarin
New England Journal of Medicine article: Dabigatran versus Warfarin in Patients with Atrial Fibrillation
New England Journal of Medicine editorial: Can We Rely on RE-LY?
To my Jewish readers I extend wishes for a sweet and healthy year. To my readers who, like me, are astronomy geeks: happy fall equinox!
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