Table Contraindications to Fluoroquinolones Contraindications include Previous allergic reaction to the drugs Certain disorders that predispose to arrhythmias (eg, QT-interval prolongation, uncorrected hypokalemia or hypomagnesemia, significant bradycardia) Use of drugs known to prolong the QT interval or to cause bradycardia (eg, metoclopramide, cisapride, erythromycin, clarithromycin, classes Ia and III antiarrhythmics, tricyclic antidepressants) Delafloxacin does not appear to cause significant prolongation of the QT interval.