Effect of Intravenous Azithromycin on the QT Interval of ICU Patients

Background: Azithromycin is a commonly prescribed antibiotic included in many first-line regimens for pneumonia. Azithromycin also carries an FDA warning for increased risk for abnormal cardiac electrical activity, including QTc prolongation. Objective: To examine the effect of intravenous azithromycin on the QT interval in a cohort of patients receiving antibiotic therapy for community acquired pneumonia. Methods: A single-center, retrospective chart review of patients admitted to the Intensive Care Unit (ICU). The primary endpoint was change in QTc 48-72 hours after antibiotic initiation. The primary outcome was analyzed using ANOVA matched comparison. Results: Between 6/1/2019 and 3/31/2020, 241 total ICU patients received doses of either antibiotic. After application of exclusion criteria, the total number of patients included in analysis was 93, including 75 azithromycin patient and 18 doxycycline patients. The baseline QTc in the azithromycin group was 449 (95% CI 438-461) and the 72-hour QTc was 442 (95% CI 427-453) with an average change in QTc of -4 ms (P = .14). No statistically significant difference was found in QTc interval change between azithromycin and doxycycline. Conclusion: In this study, azithromycin use was not associated with a statistically significant increase in QTc interval. Based on these results, for the majority of patients receiving azithromycin, QTc prolongation is not likely a major concern. However, caution may still be warranted in patients considered high risk.