Background: Azithromycin has been shown to improve gastrointestinal motility in adults and may have fewer drug interactions and reduced arrhythmogenic effects than erythromycin. We hypothesized that azithromycin is comparable to erythromycin in eliciting pharmacodynamic outcomes for antral and small bowel motility. Objective: To compare the pharmacodynamic effectiveness of azithromycin and erythromycin for eliciting antral and duodenal motility in pediatric patients who underwent antroduodenal manometry for different indications. Methods: We conducted a retrospective comparison of clinic data and manometric pharmacodynamics outcomes in patients who underwent antroduodenal manometry between 2013 and 2017.Results: Fifty-one patients mean age (AE standard deviation) 9.7 (5.4) years, received either azithromycin 3 mg/kg (n ¼ 20) or erythromycin 2 mg/kg (n ¼ 31) during antroduodenal manometry. For patients receiving erythromycin, mean area under the curve (AUC) across all eight pressure ports increased from median [95% confidence interval] 2256 [1585, 2602] to 8742 [5876, 11761] mmHg  s (P < 0.001) and mean motility index increased from 8. 63 [7.87, 9.42] to 11.98 [11.20, 12.21] (P < 0.001). For patients receiving azithromycin, mean AUC increased from 2255 [1585, 2602] to 8254 [5649, 10470] mmHg  s (P < 0.001) and motility index increased from 8. 63 [7.87,9.42] to 11.79 [11.03, 12.21] (P < 0.001). Neither mean stimulated AUC nor mean motility index was significantly different between azithromycin and erythromycin treatments. There was no significant difference in side effects between groups. Conclusions:Azithromycin and erythromycin have similar pharmacodynamic effects on antral and small bowel contractility in children. Azithromycin should be considered an acceptable alternative to erythromycin as an upper gastrointestinal tract prokinetic for children and has historically had fewer side effects than erythromycin.

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