Cholwill 1999.

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): NA Received treatment (n): NA Analysed (n): 60 Age (mean ± SD, median (IQR), median (range)): 31 (22 to 42) Weight (mean ± SD, median (IQR), median (range)): 63 ± 8 BMI (mean ± SD, median (IQR), median (range)): 23 ± 2 ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 22/20 Type of general anaesthesia: inhalational anaesthesia (N₂O, isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): orally: intraoperative morphine 0.18 mg/kg IV, postoperative codeine 60 mg PO (20 patients) or morphine IV (4 patients) Type of surgery: gynaecological laparoscopy Cyclizine Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 57 Age (mean ± SD, median (IQR), median (range)): 32 (21 to 50) Weight (mean ± SD, median (IQR), median (range)): 62 ± 8 BMI (mean ± SD, median (IQR), median (range)): 23 ± 3 ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 25/26 Type of general anaesthesia: inhalational anaesthesia (N₂O, isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): intraoperative morphine 0.18 mg/kg IV, postoperative codeine 60 mg PO (19 patients) or morphine IV (3 patients) Type of surgery: gynaecological laparoscopy Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 58 Age (mean ± SD, median (IQR), median (range)): 33 (22 to 46) Weight (mean ± SD, median (IQR), median (range)): 62 ± 9 BMI (mean ± SD, median (IQR), median (range)): 23 ± 3 ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): 19/24 Type of general anaesthesia: inhalational anaesthesia (N₂O, isoflurane) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): intraoperative morphine 0.18 mg/kg IV, postoperative codeine 60 mg PO (21 patients) or morphine IV (7 patients) Type of surgery: gynaecological laparoscopy Included criteria: ASA I or II, women undergoing day‐case gynaecological laparoscopy Excluded criteria: antiemetic drugs, pregnant or breastfeeding, body mass index (BMI) > 30 kg/m² Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, (history of PONV/motion sickness, perioperative opioids): no; duration of anaesthesia, 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?): 28% (prochlorperazine 12.5 mg IM) Cyclizine Dose: 50 mg Time point of administration: immediately before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): 16% (prochlorperazine 12.5 mg IM) Placebo Dose: 0.9% saline Time point of administration: immediately before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): 47% (prochlorperazine 12.5 mg IM)
Outcomes	Vomiting (0 to 6 hours) Outcome type: dichotomous outcome Sedation/drowsiness (0 to 6 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: UK Setting: outpatient, single‐centre Author's name: J.M. Cholwill Institution: Department of Anaesthesia, Nottingham City Hospital, Nottingham, UK Email: NA Address: Department of Anaesthesia, Nottingham City Hospital, Hucknall Road, Nottingham NG5 1PB, UK Duration of study: NA Language: English Study's primary outcome: primary outcome measures were incidence of moderate or severe nausea or vomiting and number of patients receiving escape antiemetic Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "patients were allocated randomly, with stratification for past history of PONV" Judgement comment: 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	Low risk	Quote: "the drugs were blinded to patients, investigators and recovery room staff"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "the drugs were blinded to patients, investigators and recovery room staff"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: 5 patients were withdrawn (1 required a mini‐laparotomy, and data collection was incomplete in 4). All outcomes of the remaining 175 participants were analysed before discharge. Thirteen patients were admitted after surgery: 7 with PONV (2 from the ondansetron group and 4 from the saline group) and 6 for surgical reasons. Data from these patients and from the 53 patients who received rescue antiemetics were excluded from further analysis (after discharge)
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	Unclear risk	Quote: "patient data were comparable in all groups (Table 1)" Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, (history of PONV/motion sickness, perioperative opioids): no; duration of anaesthesia, non‐smoker): unclear