A study from the University of Pittsburgh reports that some patients may be at an increased risk for Pradaxa uncontrollable bleeding problems.

Since its U.S. Food and Drug Administration’s approval in 2010, Pradaxa, or dabigatran had gotten many medical practitioners excited, according to an article in Harvard Health Blog.

Pradaxa is an anticoagulant that helps reduce the ability of the blood to clot. According to reports, it reduces the risk of stroke and blood clots, known as systemic embolism, in patients who possess non-valvular atrial fibrillation. Atrial fibrillation is the medical term describing patients suffering from an irregular heart rhythm that may let blood clots form in the heart.

The medication is specifically prescribed to prevent blood clots forming in the body’s lower extremity, a condition known as deep vein thrombosis, (DVT), or blood clots that form in the lungs (pulmonary embolism or PE).

According to the Harvard Health Blog, Pradaxa’s FDA approval came after the drug went through a “head-to-head” clinical trial with another anticoagulant medication, warfarin (brand name Coumadin) in patients who are suffering from atrial fibrillation. For decades, warfarin was the standard anticoagulant medication used to reduce the risk of stroke for atrial fibrillation patients.

However, warfarin did have a few purported drawbacks. Warfarin requires regular blood testing to ensure the patient is getting the correct dose. With too much warfarin, the patient is at risk for excessive bleeding; with too little, they’re left in danger of having a stroke.

Warfarin also comes with dietary restrictions. Foods high in vitamin K will counteract warfarin’s anticoagulant effect.

Then came Pradaxa. The reports indicate that there were some benefits to patients taking Pradaxa. It was allegedly upheld to be as effective as warfarin in preventing “stroke-causing blood clots” and appeared to cause a lesser number of serious bleeding adverse side effects.

However, more recent studies have revealed evidence of the risk of Pradaxa uncontrollable bleeding problems.

One clinical study of Pradaxa was conducted by the University of Pittsburgh that included 9,400 men and women that were covered by Medicare. According to the study, the patients all had atrial fibrillation, and none of the patients had damaged heart valves. Within this group of patients, some took Pradaxa and others took warfarin.

The study reported that 9% of the Pradaxa patients experiences a major bleed, compared to 6% of the warfarin patients. Gastrointestinal bleeding was more frequent among Pradaxa users. The researchers also found higher rates of bleeding among black patients and patients with chronic kidney disease who took Pradaxa.

The Harvard Health Blog states that after doctors had been prescribing Pradaxa for a while, they started to notice that Pradaxa was “causing more episodes of major bleeding than had been expected,” and such Pradaxa uncontrollable bleeding problems were regularly occurring.

Accordingly, as a result after seeing the number of Pradaxa uncontrollable bleeding problems occurring, the U.S. Food and Drug Administration ordered additional clinical studies to be conducted.