Seven RCTs (1,252 patients) were included.
ORs showed a significant difference between each of the three doses of ondansetron and placebo for both early and late efficacy, no difference between ondansetron and droperidol for early efficacy, and no difference between ondansetron and metoclopramide for both early and late efficacy. It should be noted that some comparisons are based on 1 trial.
For early anti-emetic efficacy, ORs for different doses of ondansetron compared to placebo were: 3.0 (95% CI: 1.8, 4.8) for 1 mg (1 trial), 3.5 (95% CI: 2.1, 5.8) for 4 mg (1 trial), and 3.8 (95% CI: 2.5, 5.8) for 8 mg (3 trials). For late anti-emetic efficacy, ORs for different doses of ondansetron compared to placebo were: 2.7 (95% CI: 1.8, 3.9) for 1 mg (2 trials), 3.2 (95% CI: 2.2, 4.7) for 4 mg (2 trials), and 3.1 (95% CI: 2.1, 4.5) for 8 mg (2 trials).
For early anti-emetic efficacy compared to intravenous droperidol, the combined OR was 0.7 (95% CI: 0.3, 1.4; 2 trials), while for early and late anti-emetic efficacy compared with intravenous metoclopramide, the ORs were 2.3 (95% CI: 0.7, 6.7; 1 trial) and 1.8 (95% CI: 0.8, 4.3; 1 trial), respectively.
The NNT point estimates for early efficacy with ondansetron, compared with placebo, were: 3.8 (95% CI: 2.6, 6.6) for 1 mg (1 trial), 3.2 (95% CI: 2.3, 5.2) for 4 mg (1 trials), and 3.1 (95% CI: 2.4, 4.5) for 8 mg (3 trials). For late anti-emetic efficacy, the NNT point estimates were 4.8 (95% CI: 3.5, 7.9) for 1 mg (2 trials), 3.9 (95% CI: 3.0, 5.7) for 4 mg (2 trials), and 4.1 (95% CI: 3.1, 6.2) for 8 mg (2 trials). Comparisons of anti-emetic efficacy of ondansetron with intravenous droperidol and intravenous metoclopramide showed no significant difference between treatments in terms of NNT.
Assessment of heterogeneity of the trials showed there was no significant effect.