Rodrigo 1994.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Ondansetron Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 38 Age (mean ± SD, median (IQR), median (range)): 24 ± 5.1 Weight (mean ± SD, median (IQR), median (range)): 53 ± 8.9 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 60.5 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: balanced (fentanyl, N₂O, isoflurane) Duration of anaesthesia (in min; as mean or median): 48 Use of perioperative opioids (if yes, which?): fentanyl, morphine Type of surgery: removal of impacted third molar teeth Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 39 Age (mean ± SD, median (IQR), median (range)): 26 ± 7.6 Weight (mean ± SD, median (IQR), median (range)): 55 ± 9.1 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA Gender (female in %): 56.4 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: balanced (fentanyl, N₂O, isoflurane) Duration of anaesthesia (in min; as mean or median): 47 Use of perioperative opioids (if yes, which?): fentanyl, morphine Type of surgery: removal of impacted third molar teeth Included criteria: 18 to 48 years of age, ASA I or II, scheduled to undergo minor oral surgery (removal of impacted third molar teeth) that could not be carried out under local anaesthesia Excluded criteria: males weighing more than 120 kg, females weighing more than 100 kg, pregnant, breastfeeding, allergic to ondansetron Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia, perioperative opioids): no; (history of PONV/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?): 6.25 mg prochlorperazine IM Placebo Dose: 2 mL saline Time point of administration: immediately before induction of anaesthesia Route of administration: IV Rescue antiemetics (if yes, which?): 6.25 mg prochlorperazine IM
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome PONV (0 to 24 hours) Outcome type: dichotomous outcome Headache (0 to 24 hours) Outcome type: dichotomous outcome Constipation (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: Glaxo (Hong Kong Ltd) supplied ondansetron Country: Hong Kong Setting: inpatient, single‐centre Author's name: M.R.C. Rodrigo Institution: Department of Maxillofacial Surgery, Dental Faculty, University of Hong Kong Email: NA Address: Block 1, Flat A8, 23 Sha Wan Drive, Pokfulam, Hong Kong Language: English Duration of study: NA Trial registry number: NA Study's primary outcome: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Judgement comment: quote: "random allocation chart"
Allocation concealment (selection bias)	Unclear risk	Judgement comment: no statement
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "double‐blind study" Judgement comment: quote: "the test drug was drawn up by the nursing officer of the operating theatre and was given by the anaesthetist, thus making it blind to patients, the anaesthetist and the surgeons"
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Judgement comment: no statement on blinding of outcome assessors
Incomplete outcome data (attrition bias) All outcomes	Low risk	Judgement comment: quote: "eighty patients were included in the study. Of these results, three patients were eliminated as instead of paracetamol two had been given oral difluisal and one Panadeine..." Reasons for exclusion described and unrelated to the 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, perioperative opioids): no; (history of PONV/motion sickness, non‐smoker): unclear