Pradaxa Side Effects May Increase Infection Risk: Study

New research suggests that side effects of Pradaxa, a relatively new anticoagulant, may leave users more vulnerable to viral infections, including one that is often fatal for children and young adults. 

Researchers from the University of North Carolina report that the blood thinner Pradaxa, which inhibits a key part of the blood clotting system known as thrombin, may also inhibit the immune system.

Experiments on mice found that those given Pradaxa increased the amount of virus that found its way to the heart. A viral infection of the heart is known as myocarditis, and the researchers say it is a significant cause of sudden death among children and young adults.

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Researchers believe that Pradaxa use could increase the risk of the flu and other viral infections as well.

Thrombin is Part of Body’s Defense Against Viruses

According to the researchers, coagulation, or blood clotting, is one of the first responses of the immune system. Researchers have always known that one part of that system, fibrin, was key in activating the immune system when the body detected a bacterial infection, which is why clotting is important at wound sites. However, the University of North Carolina researchers indicate that it appears thrombin, which is targeted by Pradaxa, is crucial in activating the immune systems defenses against viral infections, which are different from bacterial infections.

“Pradaxa inhibits clot formation by reducing fibrin deposition and platelet aggregation,” said Dr. Nigel Mackman, the lead researcher. “Importantly, Pradaxa might not only facilitate significant lifesaving effects in reducing cardiac death but may also interfere with other processes in the body.”

Mackman said study still needs to be done on whether warfarin, an older blood thinner Pradaxa was designed to replace, has any similar effects on the immune system or whether this is something specific to Pradaxa.

Pradaxa Bleeding Problems

Pradaxa (dabigatran) was introduced by drug maker Boehringer Ingelheim in October 2010, as a superior alternative to warfarin, more commonly known under the brand-name Coumadin, which has been the go-to anticoagulant treatment for decades. 

Concerns have surrounded the safety of Pradaxa since it was introduced, primarily involving a spike in reports of severe and uncontrollable bleeding associated with the medication.

During 2011, the first full year the drug was on the market, the Institute for Safe Medication Practices (ISMP) found that adverse event reports involving problems with Pradaxa surpassed all other medications regularly monitored by the group. The FDA received at least 3,781 reports involving serious injuries associated with the use of Pradaxa during 2011, including 2,367 reports of hemorrhage and 542 patient deaths.

About 200 Pradaxa bleeding lawsuits have been filed against Boehringer Ingelheim, alleging that the drug maker failed to adequately warn about the risk of serious or fatal health problems and the lack of a reversal agent to stop bleeding problems that may develop.

While warfarin has a reversal agent, vitamin K, that counters its effects rapidly in case of uncontrolled bleeding. Pradaxa has no such antidote, which many doctors say makes it more difficult to stop Pradaxa bleeding events.

In the federal court system, the Pradaxa litigation is centralized before U.S. District Judge David R. Herndon as part of an MDL, or multidistrict litigation. A case management plan has been established where a handful of cases are being prepared for early trial dates, which are expected to go to trial in August 2014.  Judge Herndon has also ordered the parties to meet every month starting in August 2013, to discuss potential Pradaxa settlement agreements.


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