Pradaxa Safety Results Questioned by Researchers

Clinical trials used to establish the safety and effectiveness of Pradaxa, a new blood thinner, are being questioned by Canadian researchers. 

In a letter published in the Therapeutics Initiative (pdf), researchers from the University of British Columbia write that the clinical trials used to gain approval for Pradaxa, known as RE-LY, were fundamentally flawed. They indicate that the drug should have never been approved based on the trial’s results.

The RE-LY clinical trials compared the effects of Pradaxa with warfarin, a blood thinner that has been on the market for decades. The trial used a double-blind method comparison between two doses of Pradaxa, but a non-blinded comparison between Pradaxa and warfarin allowed bias and errors to creep into the results, according to the letter. The clinical trials found that warfarin carried a higher risk of mortality and hospitalization over Pradaxa.

The researchers concluded that Pradaxa was prematurely approved and that it is unsafe to use for many patients. They also determined that an independent audit of the RE-LY clinical trials needs to look at irregularities in conduct, bias and some of the trial’s findings.

Pradaxa (dabigatran) was only released in October 2010, but has received more consumer complaints to the FDA’s MedWatch adverse event reporting system than 98.7% of the other drugs on the market.

Some patients and doctors report that the drug sometimes had too much of an effect on clotting, leading to hemorrhages. Other reports indicate that at times it does not have enough of an effect, resulting in pulmonary embolism or deep vein thrombosis.

According to a report by the Institute of Safe Medication Practices (ISMP), the FDA received hundreds of complaints about problems from Pradaxa within weeks of its release. Most of the cases were bleeding problems in elderly users. Overall, the FDA received 307 complaints about Pradaxa side effects in the last quarter of 2010, compared to 202 complaints involving warfarin.