Background High-dose erythromycin used as antibiotic prolongs QTc interval. Low-dose erythromycin is frequently used as a prokinetic agent, especially in patients in the intensive care unit (ICU). It is unknown whether low-dose erythromycin affects cardiac repolarisation and puts patients at risk for torsades de pointes.

Methods In this prospective study, we included ICU patients treated with erythromycin as prokinetic in a dose of 200 mg twice a day. An ECG was performed before, 15 min and 24 hours after the start of erythromycin. Cardiac repolarisation was assessed by rate-corrected analysis of the QT interval (QTc) on the ECG by two independent investigators. Starting or stopping other possibly QTc prolonging drugs during the study period was an exclusion criterion. Wilcoxon signed-rank test and Friedman's test were used for statistical analysis to assess prolongation of QTc. Primary outcome was defined by the prolongation of QTc after 15 min and 24 hours.

Results 51 patients were eligible for this study. In these patients, QTc increased significantly from 430 ms at baseline to 439 ms (p=0.03) after 15 min and 444 ms (p=0.01) after 24 hours. After 15 min and 24 hours, the upper limit of 95% CI for prolongation of QTc was well above 10 ms. No QTc-related arrhythmias were seen.

Conclusions During treatment with erythromycin in a dose of 200 mg twice a day. QTc prolonged mildly but significantly. Sequential ECG registration should be performed when low-dose erythromycin is prescribed, especially in the presence of other risk factor for QTc prolongation.