Larsson 1988.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 3 groups, monoprophylaxis
Participants	Baseline characteristics Dixyrazine Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 30 Received treatment (n): NA Analysed (n): 25 Age (mean ± SD, median (IQR), median (range)): 39 ± 10 Weight (mean ± SD, median (IQR), median (range)): 75 ± 14 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 60 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: balanced anaesthesia (fentanyl, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 129 Use of perioperative opioids (if yes, which?): 3.9 µg/kg/h fentanyl intraoperative, pethidine postoperative Type of surgery: abdominal, minor orthopaedic, thyroid, mammary Scopolamine Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 30 Received treatment (n): NA Analysed (n): 29 Age (mean ± SD, median (IQR), median (range)): 39 ± 10 Weight (mean ± SD, median (IQR), median (range)): 70 ± 12 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 50 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: balanced anaesthesia (fentanyl, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 148 Use of perioperative opioids (if yes, which?): 3.9 µg/kg/h fentanyl intraoperative, pethidine postoperative, morphine 0.15 mg/kg Type of surgery: abdominal, minor orthopaedic, thyroid, mammary Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): 30 Received treatment (n): NA Analysed (n): 26 Age (mean ± SD, median (IQR), median (range)): 40 ± 13 Weight (mean ± SD, median (IQR), median (range)): 68 ± 15 BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 53 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: balanced anaesthesia (fentanyl, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 128 Use of perioperative opioids (if yes, which?): 4.7 µg/kg/h fentanyl intraoperative, pethidine postoperative Type of surgery: abdominal, minor orthopaedic, thyroid, mammary Included criteria: 20 to 60 years of age; ASA I or II; scheduled for abdominal, minor orthopaedic, thyroid, or mammary surgery expected to last at least 1 hour; no patient was on continuous sedative or analgesic medication Excluded criteria: NA Pretreatment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia): no; (history of PONV/motion sickness, non‐smoker): unclear; (perioperative opioids): yes
Interventions	Intervention characteristics Dixyrazine Dose: 0.5 mg/kg Time point of administration: 1 hour before anaesthesia induction Route of administration: IM Rescue antiemetics (if yes, which?): droperidol Scopolamine Dose: scopolamine 0.0065 mg/kg, morphine 0.15 mg/kg Time point of administration: 1 hour before anaesthesia induction Route of administration: IM Rescue antiemetics (if yes, which?): droperidol Placebo Dose: saline Time point of administration: 1 hour before anaesthesia induction Route of administration: IM Rescue antiemetics (if yes, which?): droperidol
Outcomes	Sedation/drowsiness (at 24 hours) Outcome type: dichotomous outcome Adverse events (general notes in the publication, 6 hours' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: Sweden Setting: NA, single‐centre Author's name: Sylvia Larsson Institution: Department of Anesthesiology, University Hospital, Lund, Sweden Email: NA Address: NA Duration of study: NA Language: English Study's primary outcome: NA 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 randomly divided into three groups with 30 patients each" 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	Unclear risk	Quote: "in equal volume and in a double‐blind fashion" Judgement comment: insufficient information on blinding
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: quote: "two patients excluded because of thyrotoxic symptoms before induction of anaesthesia. 8 patients were later excluded because of following reasons: delays in operating room schedule, major surgical bleeding, anaesthesia >1 h, reoperation"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	High risk	Judgement comment: baseline characteristics (age, weight, ASA): no. Potential effect modifiers (gender, duration of anaesthesia): no; (history of PONV/motion sickness, non‐smoker): unclear; (perioperative opioids): yes