Morris 1998.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 3 groups, monoprophylaxis
Participants	Baseline characteristics Ondansetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 465 (per protocol ‐> efficacy analysis), 468 (intention to treat ‐> safety analysis) Received treatment (n): 465 Analysed (n): 465 (per protocol ‐> efficacy analysis), 468 (intention to treat ‐> safety analysis) Age (mean ± SD, median (IQR), median (range)): 45 ± 11 Weight (mean ± SD, median (IQR), median (range)): 67.4 ± 12.5 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/NA/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 35.2/NA Type of general anaesthesia: balanced anaesthesia (halothane/isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 93 Use of perioperative opioids (if yes, which?): 458 patients received intraoperative opioids (fentanyl, morphine, alfentanil), 451 patients received postoperative opioids (morphine, papaveretum) Type of surgery: major intra‐abdominal gynaecological surgery, vaginal hysterectomy Metoclopramide Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 462 (per‐protocol) Received treatment (n): 462 Analysed (n): 462 Age (mean ± SD, median (IQR), median (range)): 47 ± 11 Weight (mean ± SD, median (IQR), median (range)): 67.1 ± 12.6 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/NA/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 34.0/NA Type of general anaesthesia: balanced anaesthesia (halothane/isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 91 Use of perioperative opioids (if yes, which?): 459 patients received intraoperative opioids (fentanyl, morphine, alfentanil), 448 patients received postoperative opioids (morphine, papaveretum) Type of surgery: major intra‐abdominal gynaecological surgery, vaginal hysterectomy Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 117 (per‐protocol) Received treatment (n): 117 Analysed (n): 117 Age (mean ± SD, median (IQR), median (range)): 48 ± 12 Weight (mean ± SD, median (IQR), median (range)): 68.3 ± 11.7 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/NA/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 37.6/NA Type of general anaesthesia: balanced anaesthesia (halothane/isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 95 Use of perioperative opioids (if yes, which?): 115 patients received intraoperative opioids (fentanyl, morphine, alfentanil), 115 patients received postoperative opioids (morphine, papaveretum) Type of surgery: major intra‐abdominal gynaecological surgery, vaginal hysterectomy Included criteria: female, inpatient, at least 18 years of age, having major intra‐abdominal gynaecological surgery or vaginal hysterectomy performed under standardized general anaesthesia, hospitalized for at least 24 hours post recovery Excluded criteria: pregnant or breastfeeding, body weight > 100 kg, ASA IV or V, given drugs with known antiemetic properties, severe nausea or emesis in the 24‐hour period before receiving study medication, planned intraoperative gastric suctioning, planned intragastric tube postoperatively, known hypersensitivity to ondansetron, contraindications to metoclopramide or ondansetron as indicated in the local prescribing information, participation in another clinical trial during this study or in the 30 days before the start of this study Pretreatment: baseline characteristics (age, weight): no; (ASA): unclear. Potential effect modifiers (gender, duration of anaesthesia, history of PONV, perioperative opioids): no; (history of motion sickness, non‐smoker): unclear
Interventions	Intervention characteristics Ondansetron Dose: 4 mg Time point of administration: immediately before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 4 mg IV; if ineffective, any other antiemetic could be administered Metoclopramide Dose: 10 mg Time point of administration: immediately before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 4 mg IV; if ineffective, any other antiemetic could be administered Placebo Dose: saline Time point of administration: immediately before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): ondansetron 4 mg IV; if ineffective, any other antiemetic could be administered
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Nausea (0 to 24 hours) Outcome type: dichotomous outcome Subjects with any AE (0 to 24 hours) Outcome type: dichotomous outcome Mortality (0 to 24 hours) Outcome type: dichotomous outcome Headache (0 to 24 hours) Outcome type: dichotomous outcome Adverse events (general notes in the publication, 24 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: Australia, Canada, Denmark, France, Germany, Iceland, Israel, the Netherlands, Norway, South Africa, Sweden, United Kingdom Setting: inpatient, multi‐centre (58) Author's name: R.W. Morris Institution: Department of Anaesthetics, Princess of Wales Hospital, Coity Road, Bridgend, Mid Glamorgan, UK Email: NA Address: NA Duration of study: NA Language: English Study's primary outcome: no emesis (e.g. complete response) during the 24‐hour post‐recovery period Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: quote: "randomized" No further information on sequence generation provided
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Judgement comment: insufficient information on blinding ("double‐blind")
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: insufficient information on blinding ("double‐blind")
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: per‐protocol analysis (efficacy analysis): no missing outcome data (1074 participants were recruited, 1047 received study medication, 1044 were correctly randomized and analyzed for efficacy)
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Judgement comment: baseline characteristics (age, weight): no; (ASA): unclear. Potential effect modifiers (gender, duration of anaesthesia, history of PONV, perioperative opioids): no; (history of motion sickness, non‐smoker): unclear