Twelve RCTs were included in the review with 2,122 participants (446 participants with a previous history of motion sickness (+) and 1,676 participants with no previous history of motion sickness (-).
The average quality score was 3.5.
The test for homogeneity was P > 0.05 for studies in both the 4 mg and 8 mg groups.
Pooled OR (11 studies) in favour of 4mg ondansetron for 326 PHMS(+) participants was 3.43 (95% CI: 2.14, 5.50) which was statistically significant.
Pooled OR (11 studies) in favour of 4mg ondansetron for 1,395 PHMS(-) participants was 2.00 (95% CI: 1.59, 2.52) which was statistically significant.
The NNT values for 4 mg ondansetron for PHMS (+) and PHMS (-) participants were 3.38 (95% CI: 2.52, 5.34) and 6.37 (95% CI: 4.85, 9.30) respectively.
Pooled OR (3 studies) in favour of 8mg ondansetron for 151 PHMS(+) participants was 3.11 (95% CI: 1.40, 6.93) which was statistically significant.
Pooled OR (3 studies) in favour of 8mg ondansetron for 423 PHMS(-) participants was 2.08 (95% CI: 1.35, 3.21) which was statistically significant.
The NNT values for 8 mg ondansetron for PHMS (+) and PHMS (-) participants were 3.77 (95% CI: 2.34, 10.67) and 4.30 (95% CI: 3.10, 7.13) respectively.
There were no statistically significant differences between the studies sponsored by the manufacturers (Glaxo-Wellcome) and those conducted independently.