<prompt> This antihistaminic drug can cause cardiac arrhythmia at high dose by blocking cardiac K channels. It is most likely to be:Levo-cetrizineFexofenadineAstemizoleLoratidine  <response>: The drugs which can cause QT prolongation and Torsades de pointes and have been withdrawn from the market due to this reason are: C: Cisapride A: Astemizole T: Terfenadine You can remember CAT is cute, so these drugs cause QT prolongation. 