EDITOR—Yap and Camm emphasise the risk of torsades de pointes associated with non-cardiac drugs that prolong the QT interval.1 They comment on the fluoroquinolone antimicrobial agents grepafloxacin and sparfloxacin causing QT prolongation but also the apparent lack of this effect with levofloxacin. We recently cared for a patient who developed torsades de pointes while taking levofloxacin, which prompted us to examine retrospectively paired electrocardiograms in other patients to compare QTc intervals before and after they started treatment with this drug.

Twenty three patients who received a standard dose of 500 mg levofloxacin daily had cardiograms that could be compared for QTc prolongation. Prolongation of >30 ms was found in four patients and of >60 ms in two patients. Absolute QT …