Effect of intravenous ondansetron on QTc interval in children with gastroenteritis

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The potential for ondansetron to cause QT prolongation and fatal dysrhythmia is well-reported, including a 2011 FDA report on the topic. Few clinical trials evaluating this phenomenon in the ED setting exist, and only one is pediatric.


We have sought to determine the effect of a standardized dose of intravenous ondansetron on the QTc duration of children under 14 years of age treated for gastroenteritis-associated vomiting in a pediatric ED. This study is modeled closely after an FDA “thorough QT study”.


EGCs were obtained before and 15, 30, 45, and 60 min after a 0.15 mg/kg IV dose of ondansetron given for gastroenteritis-associated vomiting. QT intervals were measured manually with digital calipers, and the QTc interval calculated both by Bazett's (QTcB) and Fridericia's (QTcF) correction. A paired t-test comparing QTc was conducted, and frequency of categorical outcomes of prolongation > 30 msec, > 60 msec, and absolute prolongation > 450 msec, > 480 msec, and > 500 msec were evaluated.


In a 4-month period, 134 patients were included in the study, 46% were male. The average QTc prior to ondansetron administration was: QTcB 415 msec (95% CI 343–565) and QTcF 373 (95% CI 304–499). The mean difference in QTc after ondansetron was 0.4 msec for QTcB (95% CI − 35–45 msec) and 0.1 msec for QTcF (95% CI − 40–18 msec).


In these children, 0.15 mg/kg of intravenous ondansetron did not cause prolongation of QTcB or QTcF measured 15 min after administration, nor at later times.

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