Fifty controlled trials were included (n=approximately 6,437).
Intervention versus placebo: All except six trials showed a statistically significant reduction in vomiting symptoms for the study drug compared with placebo. The pooled odds ratio (OR) for each of the drug versus placebo comparisons also showed statistically significant reductions in the odds of vomiting when compared with placebo. The final ORs from the Bayesian models were: ondansetron 0.37 (95% CrI: 0.35 to 0.39; 14 trials); tropisetron 0.17 (95% CrI: 0.13 to 0.22; five trials); dolasetron 0.16 (95% CrI: 0.09 to 0.27; two trials); granisetron 0.16 (95% CrI: 0.10 to 0.20; three trials); dexamethasone 0.31 (95% CrI: 0.28 to 0.34; 13 trials); droperidol 0.48 (95% CrI 0.37 to 0.61; three trials).
Combination treatments: The lowest risk of vomiting was associated with combination treatments, with relative risks as follows: ondansetron plus droperidol 0.22 (95% CrI: 0.10 to 0.45 direct comparison; one trial), ondansetron plus dexamethasone 0.22 (95% CrI: 0.07 to 0.61 direct comparison) 0.17 (95% CrI: 0.14 to 0.21, indirect comparison) (five trials); granisetron plus dexamethasone 0.10 (CrI: 0.02 to 0.47, direct comparison; one trial); tropisetron plus dexamethasone 0.20 (95% CrI: 0.14 to 0.30, indirect comparison; two trials); dolasetron plus dexamethasone 0.21 (95% CrI: 0.12 to 0.39, indirect comparison; one trial).
Sensitivity analyses that used a sceptical prior probability showed almost identical results for ondansetron and dexamethasone, but increased the OR for other comparisons. The review also reported the most optimistic and the most pessimistic estimated risk of vomiting associated with each intervention at specific paediatric risk categories.