Pradaxa Internal Bleeding

When it comes to blood thinners prescribed to patients, there’s always at least a slight risk of internal bleeding. However, there are some medications where that probability happens to be much higher than expected. One of these blood thinners, dabigatran (marketed as Pradaxa in the United States), was originally approved by the US Food and Drug Administration for use in patients suffering from atrial fibrillation in 2010, only to have it revealed that when it comes to Pradaxa internal bleeding is much more common than with similar blood thinners like warfarin.

The Rise and Fall

Originally, the FDA and other international regulatory agencies were keen to push Pradaxa into service as a treatment for heart conditions that would replace warfarin, which requires patients prescribed the drug to be subjected to regular blood tests every one to four weeks to ensure that proper titration has occurred. Additionally, warfarin is contraindicated for several medications and is prone to causing adverse drug reactions, especially among older patients; one study appearing in the New England Journal of Medicine claims that one out of every three emergency room visits for adverse drug reactions in patients over the age of 65 is linked to warfarin directly and exclusively.

With Pradaxa not interacting with nearly as many drugs as warfarin – and with patients not required to take weekly blood tests to ensure proper levels – doctors and patients were keen to begin transitioning their patients with heart disease to the new drug. However, once Pradaxa hit the market in 2010, there seemed to be an immediate problem with serious adverse events; in the first quarter of 2012 alone, there were 932 documented cases – 120 of which were fatal. 505 of these cases involved internal bleeding, a figure that dwarfs the 176 warfarin-related bleeding events in the same time period.

Lack of Effective Treatment

One of the most frustrating problems that medical professionals have encountered with Pradaxa is that there’s nothing in the way of a useful antidote to counteract the blood thinning effects of the drug. Unlike warfarin, which can have its main function stop with a suitable dose of Vitamin K, Pradaxa internal bleeding has no known reliable antidote. Little can be done besides monitoring a patient as the drug filters out of the body, and this can take several hours – up to a day when it comes to patients with reduced or impaired kidney function.

It’s this lack of effective treatment – and the fact that cases of internal bleeding seem to be so much higher with Pradaxa than they are with warfarin – that has caused doctors, patients, and activists to question the FDA’s reasoning for approving the drug for widespread use in the US. The federal agency began a year-long review of Pradaxa in late 2011, announcing a year later that their data showed there was little difference between the rates that warfarin and Pradaxa internal bleeding occurred. However, the FDA left out any response to the criticism that Pradaxa was approved for use without an antidote. Meanwhile the methods the FDA used to conduct their evaluations have been under fire by activists for not being accurate enough. At the same time, Boehringer Ingelheim, the manufacturer of the drug, insists that it is working closely with the FDA to provide better prescription guidance to physicians – especially those with elderly patients that may be more susceptible to internal bleeding caused by Pradaxa. However, the company declined to comment on whether it would be seeking to have a lower-dose option of Pradaxa made available in the United States.

Sources:

http://www.drugwatch.com/pradaxa/bleeding/

http://www.forbes.com/sites/larryhusten/2011/12/07/fda-undertakes-safety-review-of-dabigatran-pradaxa/

http://www.philly.com/philly/blogs/healthcare/New-blood-thinner-Pradaxa-may-pose-bleeding-risk-in-elderly.html