Prophylactic ondansetron for post-operative emesis: meta-analysis of its effectiveness in patients with and without a previous history of motion sickness

The post-operative anti-emetic efficacy of 4 and 8 mg of ondansetron in adu lt patients with and without a previous history of motion sickness (PHMS) w as assessed by meta-analysis. MEDLINE and EMBASE databases were searched fo r randomized placebo-controlled trials evaluating the anti-emetic effective ness of ondansetron in a 24-h period. in the 49 studies found, a further se lection was with respect to those studies that noted the patient's previous history of motion sickness. Twelve trials involving 2122 patients; 446 pre vious history of motion sickness(+) patients and 1676 previous history of m otion sickness(-) patients met the selection criteria. The dose of 4 mg ond ansetron was 71.5% more effective in previous history of motion sickness(+) than in previous history of motion sickness(-) patients. For the 8 mg dose , the odds ratios (95% CI) were: previous history of motion sickness(+)=3.1 1 (1.40-6.93) and previous history of motion sickness(-)=2.08 (1.35-3.21). The calculated number needed to treat was also more favourable in previous history of motion sickness(+) patients for both doses of ondansetron, demon strating a higher effectiveness in this subgroup of patients.