Wilkinson 1989.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Placebo Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 95 Age (mean ± SD, median (IQR), median (range)): NA Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): 23.16/18.95 Type of general anaesthesia: inhalational anaesthesia (halothane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): no significant difference in opioid analgesic usage between the 2 groups Type of surgery: plastic surgical or orthopaedic procedure Hyoscine Assessed for eligibility (n): ‐ Enrolled (n): ‐ Randomized (n): NA Received treatment (n): NA Analysed (n): 95 Age (mean ± SD, median (IQR), median (range)): NA Weight (mean ± SD, median (IQR), median (range)): NA BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): NA Non‐smoker (%): NA History of PONV/motion sickness (%): 25.26/34.74 Type of general anaesthesia: inhalational anaesthesia (halothane, N₂O) Duration of anaesthesia or surgery (in min; as mean or median): NA Use of perioperative opioids (if yes, which?): no significant difference in opioid analgesic usage between the 2 groups Type of surgery: plastic surgical or orthopaedic procedure Included criteria: ASA I or II, elective plastic surgical or orthopaedic procedure of less than 2 hours' duration, 16 to 65 years of age, weighing between 40 and 100 kilograms, no history of gastro‐oesophageal reflux or regular antiemetic or anticholinergic medication Excluded criteria: NA Pretreatment: baseline characteristics (ASA): no; (age, weight): unclear. Potential effect modifiers (history of PONV): no; (gender, duration of anaesthesia, non‐smoker, perioperative opioids): unclear; (history of motion sickness): yes
Interventions	Intervention characteristics Placebo Dose: placebo patch Time point of administration: 7 to 12 hours before undergoing minor orthopaedic or plastic surgery Route of administration: transdermal Rescue antiemetics (if yes, which?): metoclopramide, prochlorperazine Hyoscine Dose: NA Time point of administration: 7 to 12 hours before undergoing minor orthopaedic or plastic surgery Route of administration: transdermal Rescue antiemetics (if yes, which?): metoclopramide, prochlorperazine
Outcomes	Vomiting (0 to 24 hours) Outcome type: dichotomous outcome Nausea (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: a grant from Ciba‐Geigy (New Zealand) Ltd. Country: New Zealand Setting: inpatient and outpatient, single‐centre Author's name: F.M. Davis Institution: Departments of Anaesthesia and Commmunity Health, Christchurch School of Medicine, Christchurch, New Zealand Email: NA Address: Depanment of Anaesthesia, Christchurch School of Medicine, P.O. Box 4345, Christchurch, New Zealand Duration of study: NA Language: English Study's primary outcome: incidence of vomiting Trial registry number: NA
Notes	None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "supplied by Ciba‐Geigy (NZ) Ltd. Random number lists were used to assign patients to one of two treatment groups, and a sealed enveloped containing..."
Allocation concealment (selection bias)	Unclear risk	Quote: "a sealed enveloped containing the trial medication, either Scopoderm or a placebo patch, was allocated for each patient" Judgement comment: not stated; sequentially numbered, opaque, and sealed envelope (SNOSE)
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "identical, unlabelled patches containing either hyoscine or placebo were supplied by Ciba‐Geigy (NZ) Ltd. Random number lists were used" Quote: "using a double‐blind technique" Judgement comment: insufficient information on who was blinded
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Quote: "patients were carefully interviewed either personally or by telephone by a trained independent observer"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "of the 221 patients entering the trial, 31 were subsequently excluded for the reasons outlined in Table 1"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to a study protocol or trial registry number reported
Other bias	High risk	Quote: "there were no demographic differences between the two treatment groups, each of 95 subjects, excepting that the hyoscine group contained more individuals with a past history of motion sickness (P < 0.05)" Judgement comment: baseline characteristics (ASA): no; (age, weight): unclear. Potential effect modifiers (history of PONV): no; (gender, duration of anaesthesia, non‐smoker, perioperative opioids): unclear; (history of motion sickness): yes