Randomized, double-blind study comparing the efficacy of moderate-dose metoclopramide and ondansetron for the prophylactic control of postoperative vomiting in children after tonsillectomy.

BACKGROUND Postoperative vomiting (POV) is a major cause of morbidity after tonsillectomy in children. It has been well established that anti-serotinergic agents are effective for the prophylactic control of POV in this patient group. It has been suggested that at moderate doses (0.5 mg kg(-1)), metoclopramide is also an effective agent. No study has been performed comparing the efficacy of an anti-serotinergic agent and moderate-dose metoclopramide. METHODS A total of 557 children undergoing tonsillectomy with or without adenoidectomy were randomly allocated to receive either ondansetron 0.1 mg kg(-1) or metoclopramide 0.5 mg kg(-1). All received a standardized muscle-relaxant anaesthetic and dexamethasone 0.1 mg kg(-1). The primary outcome was any vomit in the immediate postoperative period. Comparisons were made of the proportion in each group reaching the primary outcome and the time until their first vomit. The study was designed to detect equivalence. RESULTS The incidence of vomiting in the group receiving ondansetron (25.3%) was 12% lower (95% CI 4.4-19.7) than those in metoclopramide (37.3%). The time until first vomit was significantly longer in the group receiving ondansetron (hazard ratio 0.61, 95% CI 0.45-0.82). CONCLUSIONS Although the incidence of vomiting was similar, when these results are compared with a pre-specified zone of equivalence of 0-15%, it cannot be concluded that the effect of metoclopramide is equivalent to ondansetron. Survival analysis indicated that those in the metoclopramide group vomited substantially earlier. It is concluded, therefore, that ondansetron 0.1 mg kg(-1) is a superior drug to metoclopramide 0.5 mg kg(-1) for the prophylactic control of POV in children undergoing tonsillectomy.