<prompt> Cisapride was withdrawn from market due to?QT ProlongationIncreased PR intervalTeratogenicityMyocardial damage  <response>: ANSWER: A QT ProlongationREF: Lippincotts 4th ed ch: 17See previous question for list of drugs causing QT prolongationInhibition of potassium channels widens the action potential, leading to a prolonged QT interval on the electrocardiogram. Such an effect is associated with increased risk of developing life-threatening ventricular tachyarrhythmias torsades de pointes. The most common cause of QT prolongation is drug-induced, although it may also be genetic. 