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WASHINGTON -- The FDA is warning clinicians not to prescribe dabigatran (Pradaxa) to patients with mechanical heart valves, an indication for which the oral anticoagulant is not approved.

The move comes barely 2 weeks after the drugmaker Boehringer Ingelheim stopped the phase II RE-ALIGN trial, which tested three doses of the drug in patients with mechanical valves.

Investigators stopped RE-ALIGN because patients on dabigatran experienced more adverse events such as strokes, heart attacks, and thrombus formation on mechanical heart valves compared with those taking warfarin. Dabigatran patients also saw more bleeding after valve surgery associated with dabigatran compared with warfarin, the FDA said in a statement.

Dabigatran was approved in the U.S. in 2010 for the prevention of stroke in patients with nonvalvular atrial fibrillation.

Some bleeding concerns around dabigatran's approved use in atrial fibrillation arose internationally amid reports of 50 deaths attributed to the drug.

The FDA subsequently investigated the matter and determined there was no excess risk of bleeding associated with dabigatran.

Although adverse events have been associated with dabigatran's use in patients with mechanical heart valves, the drug has not been studied in patients with bioprosthetic valves, those made from natural body tissues.

Patients on bioprosthetic valves typically don't require blood thinners, Daniel Simon, MD, of Case Western Reserve University in Cleveland, told 番茄社区. However, if he encountered a patient with a natural biological valve, he would not prescribe dabigatran.

In fact, in its warning, the FDA noted that studies involving the use of dabigatran with bioprosthetic valves have not been conducted and so it cannot make any recommendation for or against its use. It urged physicians to evaluate patients on all types of prosthetic heart valves for the most appropriate medical therapy.

From the American Heart Association:

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