Multidose Ondansetron after Emergency Visits in Children with Gastroenteritis

Ondansetron improves outcomes when administered in emergency departments to children with acute gastroenteritis-associated vomiting. It is commonly prescribed at discharge to reduce symptoms, but evidence to support this practice is limited. We conducted a double-blind, randomized superiority trial involving children 6 months to less than 18 years of age with acute gastroenteritis-associated vomiting in six pediatric emergency departments. Caregivers were provided with six doses of oral ondansetron or placebo to administer in response to ongoing vomiting during the first 48 hours after enrollment. The primary outcome was moderate-to-severe gastroenteritis, defined by a score of 9 or higher on the modified Vesikari scale (scores range from 0 to 20, with higher scores indicating greater severity), during the 7 days after enrollment. Secondary outcomes included the presence of vomiting, the duration of vomiting (defined as the time from enrollment to the last vomiting episode), the number of vomiting episodes within 48 hours after enrollment, unscheduled physician visits within 7 days after enrollment, and receipt of intravenous fluids. A total of 1030 children underwent randomization. Moderate-to-severe gastroenteritis occurred in 5.1% (23 of 452 participants for whom data were available) in the ondansetron group and 12.5% (55 of 441) in the placebo group (unadjusted risk difference, -7.4 percentage points; 95% confidence interval [CI], -11.2 to -3.7). After adjustment for site, weight, and missing data, ondansetron was associated with a lower risk of moderate-to-severe gastroenteritis than placebo (adjusted odds ratio, 0.50; 95% CI, 0.40 to 0.60). Although we did not observe any meaningful difference between the groups in the presence or median duration of vomiting, the total number of vomiting episodes within 48 hours after enrollment was lower with ondansetron than with placebo (adjusted rate ratio, 0.76; 95% CI, 0.67 to 0.87). The percentage of children who had unscheduled health care visits and the percentage who received intravenous fluids after enrollment did not differ substantially between the groups. The incidence of adverse events also did not differ meaningfully between the groups (odds ratio, 0.99; 95% CI, 0.61 to 1.61). Among children with gastroenteritis-associated vomiting, the provision of ondansetron after an emergency department visit led to lower risk of moderate-to-severe gastroenteritis during the subsequent 7 days than the provision of placebo. (Funded by the Canadian Institutes of Health Research and others; ClinicalTrials.gov number, NCT03851835.).