Doctors should exercise caution in using Boehringer Ingelheim’s new stroke prevention pill Pradaxa, following 256 cases of fatal bleeding, but the benefits of the medicine still outweigh its risks, European regulators said on Friday. Concern about the safety of Pradaxa has risen in recent weeks following the growing number of deaths. Of the total of 256 fatal bleedings worldwide as of Nov. 6, there were 21 in the Europe Union. Pradaxa is the first in a new class of medicines aimed at replacing the old and problematic drug warfarin. It is designed to prevent strokes in patients with atrial fibrillation, a form of irregular heartbeat common among the elderly.