There’s a new type of blood thinner on the market – and it’s making a lot of American heart doctors nervous. Blood thinners are used to prevent strokes caused by blood clots, especially in patients with atrial fibrillation. Nearly 35 million Americans take this class of prescription medication. The oldest in this class of medications is Coumadin (warfarin) and has been around for approximately sixty years. The drug requires regular blood monitoring and frequent doctor follow ups. It’s not a safe drug by any means, and is one of the biggest causes of emergency room fatalities in the United States. But at least physicians know how to handle it.
The new drugs are notable in how they stop clotting in a different way than warfarin. Instead of thinning blood by blocking Vitamin K, these new drugs go straight to the source by inhibiting thrombin, a major clotting protein. There are two thrombin-inhibitors on the market right now, with the most popular named Pradaxa (created by a German pharmaceutical company, Boehringer Ingelheim) and Xarelto (manufactured by Johnson & Johnson). A third, named Eliquis (manufactured by Bristol-Myers Squibb Pharmaceuticals), is currently under review by the FDA.
So, what is making so many top cardiologists wary about these new blood thinners? Well, these new drugs have no known antidote – where Vitamin K administered to a patient on warfarin will restart the clotting process. All blood thinners are dangerous, especially when taken by the elderly, but a blood thinner with no available reversal agent to stop the blood thinning process is even more dangerous than Coumadin. Elderly patients are prone to falls, which can result in a bruise or a broken bone, but rarely death. However, a fall in a patient taking Pradaxa (also known as dabigatran etexilate) can easily become fatal, especially if a hospital is unable to stop bleeding. The nonprofit Institute for Safe Medication Practices estimates that 542 deaths in 2011 were associated with Pradaxa. This number tops all the deaths attributable to all other medications tracked by the organization, including warfarin – which is a sobering statistic.
Many top doctors refuse to switch their patients to Pradaxa due to these risks. In the words of Dr. Richard Besdine, the director of the Center for Gerontology at Brown University, “If there’s an adverse event lurking in the closet for a new drug, it’s most likely to come out in patients that are old and frail and taking multiple medications. They’re the canary in the coal mine.” Dr. Besdine has only switched two of his hundred elderly patients from warfarin for this reason. Hopefully as more physicians and patients learn of the significant increased risks associated with use of Pradaxa, they will resist the aggressive drug detailing and direct-to-consumer marketing hype that surrounds Pradaxa. Right now, the only one who needs Pradaxa the most is Boehringer Ingelheim.
One important note about Pradaxa is that the drug was initially approved with a warning label that did not include any special precautions for patients with severe kidney dysfunction, leading many doctors to forego kidney tests for patients switching to Pradaxa. In the less than two years that Pradaxa has been on the market, however, it has become clear that elderly patients with renal insufficiency are at a much higher risk of suffering fatal or catastrophic bleeding episodes (including gastrointestinal bleeding, intracranial hemorrhage, and heart attacks) while on Pradaxa, such that patients should be routinely monitored for kidney function while on the drug. Patients whose kidneys are not functioning properly are unable to efficiently clear the drug from their bodies, and end up having a buildup of toxic levels of the drug in their system. The recent recommendation that patients receive routine blood testing while on Pradaxa is sadly ironic, in that the biggest purported advantage of Pradaxa over Coumadin is that patients on Pradaxa do not require routine blood tests that are necessary with warfarin therapy.