The regulatory trial for Xarelto, a popular blood-thinning medication, used a faulty measuring device, according to an investigation performed by the online medical journal BMJ (formerly called the British Medical Journal).

What Is Xarelto?

Xarelto (generic name rivaroxaban) is the most widely-prescribed medication for stroke prevention in the US. It was approved by the FDA in July 2011 for use in the US and in May 2013 by the European Medicines Agency (EMA). Xarelto is manufactured by Bayer and marketed in the US by the Janssen Pharmaceuticals arm of Johnson & Johnson.

A Faulty Measuring Device

The FDA regulatory trial concluded that Xarelto was less likely to cause major bleeding to ischaemic stroke in non-valvular atrial fibrillation patients in comparison to warfarin, a competing medication. However, the BMJ’s investigation found that the medical device used for measuring patients’ warfarin levels gave results that were too low. Doctors in the study responded to the low readings by giving patients more warfarin, which caused increased bleeding compared to Xarelto.

What Is Atrial Fibrillation?

Atrial fibrillation (commonly called AF or AFib) is a type of irregular heartbeat meaning that sometimes the heart may beat too slow or too fast. People with AF can be at risk for developing clots in the heart which can block an artery to the brain, causing an ischaemic stroke. Depending on a patient’s specific needs, one of the ways AF can be treated is by using anticoagulants (blood thinners). Both Xarelto and warfarin are considered anticoagulants.

BMJ Calls for Additional Research

The BMJ investigation calls into question the study’s findings and has recommended an independent investigation into the results to see if they significantly impact patient safety. Thomas Marcinicak, a former FDA drug reviewer, told CBS News: “The care for the warfarin control arm patients [in the regulatory study] appears to have been compromised.”

Researchers Deny Safety Risk

However, the New England Journal of Medicine published a letter from the Clinical Research Institute (CRI) at Duke University saying that a new analysis of the data taking the faulty device into account resulted in no “significant clinical effect on the primary efficacy and safety outcomes in the trial.” It should be noted, however, that CRI performed the original regulatory trial on behalf of Bayer.   If you have taken Xarelto and have concerns about how it was regulated or whether it caused side effects like severe bleeding, talk to our lawyers. You could be entitled to reimbursement for medical costs, lost wages, and more.