ObjectiveTo assess the evidence for the safety and effectiveness of antiemetics on gastroenteritis-induced vomiting in children and adolescents.DesignSystematic review.Data SourcesThe Cochrane Central Register of Controlled Trials, MEDLINE and EMBASE searched from 1980 to March 2012.MethodsMethods included comprehensive searches, data synthesis, meta-analysis and mixed treatment comparisons (MTC).Review methodsReference lists were checked, and missing or inconsistent data were sought from trial investigators. Randomised controlled trials comparing antiemetics in participants younger than 18 years and who were vomiting due to acute gastroenteritis. Four meta-analyses and three MTC were carried out.Results10 trials (1479 participants) and five treatments were included: dexamethasone, dimenhydrinate, granisetron, metoclopramide and ondansetron. There was clear evidence that ondansetron (oral or intravenous) compared with placebo increased the proportion of patients with cessation of vomiting (orally administered) (RR 1.44, 95% CI 1.29 to 1.61), reduced the immediate hospital admission rate (orally administered) (RR 0.40, 95% CI 0.19 to 0.83) and the need for intravenous rehydration therapy (orally administered) (RR 0.41, 95% CI 0.29 to 0.59). No significant difference was noted in the revisit rates, but ondansetron was associated with an increase in episodes of diarrhoea. There was no evidence for the use of dexamethasone or metoclopramide and limited evidence that dimenhydrinate or granisetron increased the cessation of vomiting. The MTC analysis suggested that ondansetron was the most likely treatment to stop the child vomiting. Nine studies were carried out in secondary care and one in primary care.ConclusionsThis systematic review used a method novel to this clinical area and found clear evidence that ondansetron was the most likely treatment to allow oral rehydration therapy to commence. Given the significance of these results, the authors urge healthcare policy makers to consider the wider use of ondansetron in secondary care. Furthermore, randomised controlled trials are needed to investigate the effectiveness of antiemetic treatment in primary care (including ambulatory care interventions).