Chen 1996.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Metoclopramide Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 25 Received treatment (n): 25 Analysed (n): 24 Age (mean ± SD, median (IQR), median (range)): 40.1 ± 8.8 Weight (mean ± SD, median (IQR), median (range)): 55.7 ± 8.0 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 21/30 Type of general anaesthesia: inhalational anaesthesia (isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 106.0 Use of perioperative opioids (if yes, which?): 17.4 mg methadone, 11 pethidine Type of surgery: abdominal hysterectomy or ovarian surgery Ondansetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 25 Received treatment (n): 25 Analysed (n): 25 Age (mean ± SD, median (IQR), median (range)): 39.7 ± 9.0 Weight (mean ± SD, median (IQR), median (range)): 56.2 ± 7.4 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 12/20 Type of general anaesthesia: inhalational anaesthesia (isoflurane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 112.7 Use of perioperative opioids (if yes, which?): 19 mg methadone, 17 pethidine Type of surgery: abdominal hysterectomy or ovarian surgery Included criteria: ASA I or II, 18 to 60 years of age, scheduled for abdominal hysterectomy or ovarian surgery Excluded criteria: preexisting nausea or vomiting, antiemetics or opioids given in the 24 hours before surgery, pregnancy, gastro‐oesophageal reflux, alcohol or drug abuse Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, history of PONV/motion sickness, perioperative opioids): no; (non‐smoker): unclear
Interventions	Intervention characteristics Metoclopramide Dose: 10 mg Time point of administration: end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): 42% (prochlorperazine 12.5 mg IM) Ondansetron Dose: 4 mg Time point of administration: end of surgery Route of administration: IV Rescue antiemetics (if yes, which?): 36% (prochlorperazine 12.5 mg IM)
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Vomiting (0 to 4 hours) Outcome type: dichotomous outcome Vomiting (12 to 24 hours) Outcome type: dichotomous outcome Nausea (0 to 24 hours) Outcome type: dichotomous outcome Complete response (no PONV) in 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: China Setting: inpatient, single‐centre Author's name: P.P. Chen Institution: Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, NT, Hong Kong Email: NA Address: NA Language: English Duration of study: NA Trial registry number: NA Study's primary outcome: incidence of PONV
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Judgement comment: quote: "allocated randomly to receive either ondasetron 4 mg or metoclopramide 10 mg using a series of sealed envelopes" Insufficient information on the sequence generation process
Allocation concealment (selection bias)	Unclear risk	Judgement comment: quote: "allocated randomly to receive either ondasetron 4 mg or metoclopramide 10 mg using a series of sealed envelopes" Detailed information on envelopes is missing (SNOSE)
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Judgement comment: quote: "double‐blinded" Insufficient information on blinding
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Judgement comment: quote: "sedation, nausea and vomiting were assessed by an investigator blinded to the study drug"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: quote: "twenty‐five patients were initially recruited into each Group. One Patient in the metoclopramide group was excluded after she developed post‐operative respiratory depression" Reasons for missing data from 1 patient were described and are unlikely related to outcomes of interest
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, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, history of PONV/motion sickness, perioperative opioids): no; (non‐smoker): unclear