Ondansetron vs metoclopramide: 19 RCTs (2502 patients).
Ondansetron vs droperidol: 23 RCTs (3863 patients).
Droperidol vs metoclopramide: 22 RCTs (1584 patients).
Heterogeneity was statistically significant for all drug comparison (P < 0.05). OR are reported for ratio of odds for first drug to the odds of the second drug.
Ondansetron vs metoclopramide: There was a non-significant trend for ondansetron to be better than metoclopramide in reducing post-operative nausea. OR for nausea (10 RCTs, 1697 patients) = 0.70 (95% CI: 0.45, 1.10; P = 0.125). Ondansetron was significantly better than metoclopramide in reducing post operative vomiting. All studies but two, showed greater efficacy of ondansetron over metoclopramide. OR for vomiting (17 RCTs, 2272 patients) = 0.43 (95% CI: 0.31, 0.61; P < 0.001).
Ondansetron vs droperidol: these were equally effective in preventing postoperative nausea. Overall OR for nausea (13 RCTs, 2743 patients) = 0.99 (95% CI: 0.66, 1.47; P > 0.9). Ondansetron was significantly more effective than droperidol in preventing postoperative vomiting. Overall OR vomiting (22 RCTs, 3750 patients) = 0.70 (95% CI: 0.52, 0.94; P= 0.018).
There was substantial variability among studies in the relative efficacy of droperidol and ondansetron.
Subgroup analysis showed that ondansetron was significantly better than droperidol in preventing vomiting in children (6 RCTs): OR = 0.49 (95% CI: 0.30, 0.80; P < 0.01), but not in adults (11 RCTs): OR = 0.87 (95% CI: 0.61, 1.25). There was no difference in the propofol induction group.
Droperidol vs metoclopramide: Droperidol was significantly better than metoclopramide in preventing both postoperative nausea and post operative vomiting. OR nausea (15 RCTs, 1021 patients) = 0.66 (95% CI: 0.48, 0.90; P = 0.008). OR vomiting (20 RCTs, 1374 patients) = 0.68 (95% CI: 0.54, 0.85; P = < 0.001). Subgroup analysis showed that droperidol was significantly better than metoclopramide in preventing vomiting in women and all adults but there was no difference in children. Children (7 RCTs): OR = 0.63 (95% CI: 0.36, 1.10). Adults (13 RCTs): OR = 0.70 (95% CI: 0.57, 0.86; P < 0.001). Women (13 RCTs): OR = 0.70 (95% CI: 0.57, 0.86; P < 0.001).
Adverse effects: Ondansetron vs metoclopramide (4 RCTs, 1285 patients). Ondansetron vs droperidol (7 RCTs, 2403 patients).
Droperidol vs metoclopramide (13 RCTs, 936 patients). None of the drugs differed significantly for any adverse effects.