SummaryThe efficacy and safety of ondansetron in preventing postoperative nausea and vomiting.fol1owing Postoperative nausea and vomiting are complications in 20% to 40% of general anaesthesia cases [I]. Women undergoing gynaecological surgery are particularly at risk of experiencing these problems. In the absence of any antiemetic treatment, the incidence of nausea and vomiting after gynaecological surgery can range from 58% to 80% [2, 31. Ondansetron is a selective antagonist of 5-hydroxytryptamine type 3 (5HTJ receptors, with little or no clinically relevant effects on dopamine or other receptors. Initial studies in the guinea-pig [4] showed that a dose of 0.001 mg.kg-l given by intraperitoneal injection had a positive effect on gastric kinetics equivalent to that of 5 mg.kg-' metoclopramide. Furthermore, ondansetron is an effective antiemetic in patients receiving cancer chemotherapy [5, 61 or radiotherapy [7].Recent studies have evaluated the efficacy of intravenously administered ondansetron 8 mg in the prevention and treatment of postoperative nausea [8-1 I], and also orally administered ondansetron 16 mg in the prevention of postoperative nausea and vomiting [12].In this present study, the antiemetic effect of ondansetron in the prevention of postoperative nausea and vomiting was investigated in patients undergoing major gynaecological surgery.