Announcement of Experimental Pradaxa Antidote Raises Important Questions for Pending Lawsuits

The manufacturer of the blood-thinning drug Pradaxa announced recently that it has developed an experimental antidote that causes an “immediate, complete” reversal of Pradaxa’s anticoagulating effect.

Pradaxa is prescribed to reduce the risk of stroke in people who have atrial fibrillation (irregular heartbeat). However, since obtaining FDA approval in 2010, Pradaxa has become the target of about 2,000 federal and state lawsuits.

Many of those legal actions are on behalf of Pradaxa users who suffered an injury, such as a fall or a car accident, that resulted in internal bleeding. Physicians were unable to stop the bleeding through normal measures because of Pradaxa’s anticoagulation effect. Pradaxa has been linked to the deaths of more than 1,000 people in the U.S. during 2011-2012, according to FDA “serious adverse event” reports.

Many plaintiffs allege that the German manufacturer, Boehringer Ingelheim, should not have introduced Pradaxa on the market until an antidote had been developed, and that without an antidote, Pradaxa patients have a much greater likelihood of dying due to irreversible bleeding than patients who take warfarin, the drug Pradaxa was designed to replace. Plaintiffs also allege that Boehringer Ingelheim failed to warn health professionals and patients about the risk of irreversible bleeding, in the event of a cerebral hemorrhage or gastrointestinal bleed.

Development of an antidote now or in the future will not give Boehringer Ingelheim a defense in pending or new lawsuits brought on behalf of patients who have used Pradaxa before an antidote becomes available. To the contrary, the development of an antidote now poses significant questions that will no doubt be raised in the pending and future lawsuits:

• When did Boehringer Ingelheim begin its research to develop an antidote for Pradaxa?

• Did the manufacturer seek to develop an antidote because it was aware that Pradaxa patients would be exposed to an increased risk of serious harm or death due to irreversible bleeding?

• If Boehringer knew of the increased risk, was it wrong to release the drug before an antidote was developed?

• Why did Boehringer fail to warn doctors and patients of the risk, even as it was working to address that risk through research to develop an antidote?

• Did Boehringer begin work on an antidote in response to the thousands of lawsuits that were filed beginning in 2011?

At the American Heart Association’s Scientific Sessions 2013, held in Dallas in November, a Boehringer Ingelheim scientist presented results from a clinical study, which were also announced in a news release. The announcement was that an “investigational fully humanized antibody fragment rapidly reversed the anticoagulation effect of dabigatran in healthy male volunteers.”

The Boehringer Ingelheim clinical study involved 145 healthy male subjects who were given doses of Pradaxa for four days and then given the antidote. The experimental antidote achieved “immediate, complete and sustained reversal” of anticoagulation. The reversal was detected as quickly as within 5 minutes.

However, it may be a few years before the experimental antidote is approved. The Boehringer scientist said the company will begin testing the antidote on Pradaxa patients next year. In addition to confirming the antidote’s effectiveness at reversing blood-thinning, the researchers must confirm that the antidote causes no serious side effects. That will require more and bigger trials.

Pradaxa prevents blood clots by attaching and disabling thrombin, an enzyme that is essential to the blood-clotting process. The antidote is a protein that adheres to Pradaxa and thus prevents it from attaching to thrombin.

To learn more about Pradaxa and about possible legal action related to use of the drug, see our page on Pradaxa Use and Severe Bleeding.