The Problem With Coumadin
Until recently, most people with atrial fibrillation who needed anticoagulation therapy to prevent stroke had only one choice - Coumadin. Coumadin is a very effective drug when used appropriately, but using it appropriately is difficult and inconvenient for both doctors and patients. Stabilizing the dose of Coumadin requires frequent blood tests and dosage adjustments over a period of weeks or even months. Without these careful adjustments, however, Coumadin can cause problems. If you don't take enough Coumadin, the risk of stroke is not reduced. If you take too much, severe bleeding can result - including brain hemorrhage. Because of the difficulty in administering the drug properly, studies have documented that only about half the patients who should take Coumadin are receiving it appropriately.
In recent years, several drug companies have been working hard to find practical substutites for Coumadin. Three have undergone extensive testing - dabigatran, rivaroxaban, and apixaban - and the first two have been approved by the FDA in the United States. The major advantage of each of these new drugs is that they can be given as a standard twice-a-day (dabigatran and apixaban) or once-a-day (rivaroxaban) dose, without the need for blood tests or constant dosage adjustment.
The first of these to gain FDA approval, and the one with which there is the most real-world experience so far, is dabigatran. The advantages or disadvantages of the new "Coumadin substitutes," relative to one another, have yet to be worked out. But so far, most cardiologists are defaulting to dabigatran, chiefly because of the broader experience and comfort level they have with this drug.
The safety and effectiveness of dabigatran was tested in the RE-LY trial, in which more than 18,000 patients with atrial fibrillation in 44 countries were randomized to receive either one of two doses of dabigatran, or carefully administered Coumadin therapy. Investigators measured the strokes and other blood clotting events that occurred in these patients during drug treatment. They concluded that patients receiving higher-dose dabigatran (150 mg) did better than those on Coumadin (that is, they had fewer strokes), while those receiving lower-dose dabigatran (110 mg) did equally well as those on Coumadin. The incidence of major bleeding side effects were equal to (with higher dose dabigatran) or less than (with lower dose dabigatran) those seen in patients taking Coumadin. (In the U.S, the FDA has approved only the 150 mg dose.)
The major non-bleeding-related side effect with dabigatran was heartburn, which was severe enough to require stopping the drug in less than 10% of patients.
Because using Coumadin is so difficult (and is often managed so poorly in the real world), most experts now recommend dabigatran over Coumadin for preventing strokes in atrial fibrillation. However, sometimes Coumadin may still be is still the preferred option. Coumadin remains a good choice in people who have already been completely stabilized on that drug, or who balk at having to take a pill twice a day, or who simply cannot afford dabigatran.
It is certainly possible that as time goes by either rivaroxaban or apixaban will prove to be better options, for one reason or another, than dabigatran. However this competition finally works itself out, the good new for patients with atrial fibrillation (not to mention their doctors) is that Coumadin is no longer the only choice for reducing the risk of stroke.
Connolly SJ, Ezekowitz MD, Yusuf S, et al. Dabigatran versus warfarin in patients with atrial fibrillation. N Engl J Medicine 2009; DOI:10.1056.NEJM0a0905561.