Since its approval in the United States in October 2010 dabigatran (Pradaxa) has been prescribed 3.2 million times to more than 600,000 patients with nonvalvular atrial fibrillation (AF), according to its manufacturer, Boehringer Ingelheim. The company also announced that, based on the pivotal RE-LY trial, the “Clinical Studies” section of the drug’s prescribing information now includes the statement that 150 mg twice daily of dabigatran “was superior in reducing ischemic and hemorrhagic strokes relative to warfarin.”

But the news about dabigatran is not entirely upbeat. According to new data compiled by QuarterWatch (PDF), in 2011 the FDA received more safety reports about dabigatran than any other drug. The data are not entirely unexpected, since the bleeding complications of dabigatran are well known and physicians are more likely to report adverse events associated with new drugs. The drug that dabigatran was designed to replace, warfarin (Coumadin), was the second most reported drug, and has been high on the FDA list for many years.

Dabigatran was the subject of  3,781 serious adverse events reported to the FDA in 2011. This included 542 patient deaths and 2,367 hemorrhages. Warfarin  was the subject of  1,106 serious adverse events, including 72 deaths.

QuarterWatch noted that the difference between the two anticoagulants “could be at least partly explained by differences in the reporting rate for an older generic drug with many manufacturers, and a newly launched brand name drug being promoted by a large sales force.” But, according to QuarterWatch:

“What is clear, however, is that the FDA’s system is receiving a strong signal about this safety issue. A large share of dabigatran reports (79%) come from health professionals, suggesting that despite this well-known drug risk the bleeding was unexpected or unusually severe.”

QuarterWatch notes that the rapid uptake of dabigatran is probably due to its ease of use– no frequent INR tests are required– and the lack of drug interactions. One likely source of complications is the use of the standard 150 mg dose in older patients or those with renal dysfunction. The label now recommends that physicians “assess renal function during therapy as clinically indicated” but QuarterWatch wonders “whether this modest language will lead to safer use.”
Click here to read the Boehringer press release…