Moxifloxacin Does Increase the Corrected QT Interval

Abstract
SIR—We wish to respond to the letter of Iannini et al. [1], which contains several inaccuracies. These authors contend that the corrected QT (QTc) interval in an individual normally fluctuates by up to 70 ms over 24 h, but we believe they are, erroneously, quoting the value for QT interval variability rather than the value for QTc interval variability. To update the reader, we have provided data from 3 of 6 trials that show that there is no substantial circadian variability in the QTc interval.