Safety profile of blockbuster blood thinner comes under question

Posted: Published on July 24th, 2014

This post was added by Dr Simmons

A new investigation has raised fresh questions about a bestselling prescription medication to reduce stroke risk in those with the heart rhythm disorder known as atrial fibrillation.

Published Tuesday in the journal BMJ, a package of articles suggests that patients taking the drug dabigatran (marketed since 2010 as Pradaxa) may have a higher risk of life-threatening bleeding episodes than physicians and regulators had been led to believe.

The BMJ probe also suggests that there may be safety benefits to monitoring Pradaxa's anticoagulant effect on individual patients -- a practice deemed unnecessary by the Food and Drug Administration when it approved the medication's marketing four years ago.

Beneath these carefully worded questions of patient safety, the authors write, lie issues of integrity and transparency in the presentation by Pradaxa's manufacturer, Boehringer-Ingelheim, of early clinical trial data and of safety data collected since the drug hit the market. The judgment of U.S. and European drug regulators also comes in for questioning.

In an apparent bid to position Pradaxa as an improvement on a long-used medication, Boehringer-Ingelheim "withheld from the [FDA's] regulators important analyses regarding how to use the drug as safely and effectively as possible," wrote BMJ's investigations editor, Deborah Cohen.

Today, millions of patients across the globe are taking Pradaxa. As of December 2011 -- about a year after Pradaxa became available -- Boehringer-Ingelheim reported that it had been notified of 9,049 bleeding events among patients taking dabigatran, including 368 deaths. Under the terms set by the FDA and its European counterpart, Cohen wrote, some of those patients may have had their blood over-thinned, raising the risk of bleeding, a problem that might have been averted had regulators required closer monitoring of patients taking the drug.

But first, a bit of explanation.

In 2010, before the blood thinner Pradaxa became a blockbuster prescription drug with annual sales worth $2 billion in the United States, it was known simply as dabigatran. Food and Drug Administration regulators fast-tracked the drug for consideration because it promised to be the first new stroke reduction treatment for patients whose heart rhythms were erratic since an anticoagulant named warfarin was introduced in the 1950s.

Pradaxa's commercial promise turned not only on its ability to lower stroke risk in this population, but also on the practical benefits it promised to offer over warfarin.

Repurposed in the 1950s from its original use as a rat poison, warfarin's blood-thinning effects had to be monitored with monthly or even biweekly blood draws, and could easily be knocked off-kilter by changes in diet, season and aging. Because it reduced stroke risk by lowering clotting factors in the blood, one of the unavoidable dangers of taking warfarin was the risk of spontaneous bleeding episodes or uncontrolled bleeding in cases of trauma. But patients' unpredictable responses to warfarin -- the reason why blood monitoring is essential -- compounded these patients' risks for such episodes.

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Safety profile of blockbuster blood thinner comes under question

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