Effects of Azithromycin and Moxifloxacin Used Alone and Concomitantly With QTc Prolonging Medications on the QTc Interval

Abstract

Objectives: The goals of this study were to determine how frequently azithromycin and moxifloxacin were used in combination with other drugs that cause QTc prolongation, describe the effects these combinations have on QTc interval length, determine the incidence of QTc prolongation in patients on these medication combinations, and identify risk factors associated with QTc interval prolongations in patients on these medication combinations. Methods: A retrospective chart review was performed on patients who received at least two doses of azithromycin or moxifloxacin. It was noted whether these patients received other medications that prolonged the QTc interval. ECG information was grouped into daily phases depending on whether the patient was at baseline, receiving antibiotic therapy, QTc prolonging medication therapy, or concomitant therapy. These data were compared using a repeated measures ANOVA. Results: Patients received concomitant antibiotic-QTc prolong medication therapy in 70% of cases analyzed. In all patients on concomitant therapy there was no significant difference in any measured ECG data (all p-values > 0.26). In those who were on azithromycin and experienced QTc prolongation there was a significant difference in RR interval length (p=0.034). In those that experienced QTc prolongation on moxifloxacin there was a significant difference in QT (p=0.0033) and QTcF (p=0.0089) length. Conclusions: These medication combinations are used frequently in the hospital. These medications may not increase the QTc interval length in the general population but more research is warranted in this area to confirm this finding.