FDA analysis of dabigatran versus warfarin for nonvalvular AF questioned

A new study has found a greater bleeding risk associated with the use of dabigatran (Pradaxa, Boehringer Ingelheim) in patients with nonvalvular atrial fibrillation (AF) than that cited on initial FDA approval of the drug.

Earlier in 2014 FDA found that the use of dabigatran versus warfarin for treating older patients with nonvalvular AF resulted in a lower risk of clot-related strokes, bleeding in the brain, and death in these patients. The FDA study was published online in Circulation on October 30.

According to study results dabigatran at a dose of 150 mg twice daily had the greater magnitude of effect for each outcome in these AF patients, who were new users of the drug. This result was similar to that of the RE-LY clinical trial. The only caveat was that dabigatran was associated with an increased risk of major gastrointestinal (GI) bleeding compared with warfarin in this patient cohort.

Findings from another study, however, have conflicted with this FDA analysis. In a study published online in JAMA Internal Medicine on November 3 the use of dabigatran was found to be associated with higher risks not only for GI bleeding but also for major bleeding when compared with the use of warfarin in nonvalvular AF patients. Nevertheless, those patients receiving warfarin had a higher risk of intracranial bleeding.

The latter study found that those patients taking dabigatran had a 9% rate of major bleeding, as compared with almost a 6% rate in those taking warfarin, a significantly greater bleeding risk than that cited when the drug was FDA approved.

Both studies included patients aged 65 years or older enrolled in Medicare, with over 134,000 patients evaluated in the FDA study led by David J. Graham, MD, MPH, of FDA’s Center for Drug Evaluation and Research, and about 9,400 included in the study led by Immaculada Hernandez, PharmD, of the University of Pittsburgh.

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