Semple 1992.

Study characteristics
Methods	Study design: randomized controlled trial Study grouping: 2 groups, monoprophylaxis
Participants	Baseline characteristics Hyoscine patch Assessed for eligibility (n): NA Enrolled (n): NA Randomized (n): NA Received treatment (n): NA Analysed (n): 37 Age (mean ± SD, median (IQR), median (range)): 46 (28 to 64) Weight (mean ± SD, median (IQR), median (range)): 68.5 (49 to 86) BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (enflurane/N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 72 Use of perioperative opioids (if yes, which?): fentanyl for induction, 77.5 mg morphine postoperatively Type of surgery: abdominal hysterectomy Placebo Assessed for eligibility (n): NA Enrolled (n): NA Randomized (n): NA Received treatment (n): NA Analysed (n): 30 Age (mean ± SD, median (IQR), median (range)): 45.5 (31 to 63) Weight (mean ± SD, median (IQR), median (range)): 68 (54 to 97) BMI (mean ± SD, median (IQR), median (range)): NA ASA I/II/III/IV (n): NA/NA/0/0 Gender (female in %): 100 Non‐smoker (%): NA History of PONV/motion sickness (%): NA Type of general anaesthesia: inhalational anaesthesia (enflurane/N₂O) Duration of anaesthesia or surgery (in min; as mean or median): 62 Use of perioperative opioids (if yes, which?): fentanyl for induction, 82.5 mg morphine postoperatively Type of surgery: abdominal hysterectomy Included criteria: 18 to 65 years of age, ASA I or II, requiring general anaesthesia for abdominal hysterectomy Excluded criteria: NA 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 Hyoscine patch Dose: NA Time point of administration: 2 hours before operation Route of administration: transdermal patch Rescue antiemetics (if yes, which?): cyclizine 50 mg IM Placebo Dose: NA Time point of administration: 2 hours before operation Route of administration: transdermal patch Rescue antiemetics (if yes, which?): cyclizine 50 mg IM
Outcomes	Vomiting (0 to 2 hours) Outcome type: dichotomous outcome Vomiting (day 1 after PACU) Outcome type: dichotomous outcome Visual disturbances (e.g. blurred vision) (first postoperative day, day 2, day 3) Outcome type: dichotomous outcome Adverse events (general notes in the publication, 3 days' observation) Outcome type: general notes on side effects
Identification	Sponsorship source: NA Country: UK Setting: inpatient, single‐centre Author's name: P. Semple Institution: York District Hospital Email: NA Address: Department of Anaesthesia, York District Hospital, Wigginton Road, York YO3 7HE, UK 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	Judgement comment: quote: "randomly allocated". 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 placebo was a standard waterproof dressing (Johnson and Johnson) and each hyoscine patch was covered by a similar dressing, so that its identity could not be distinguished from placebo by patient or assessor. The patches were applied by a nurse who was not involved with subsequent assessment"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "the placebo was a standard waterproof dressing (Johnson and Johnson) and each hyoscine patch was covered by a similar dressing, so that its identity could not be distinguished from placebo by patient or assessor. The patches were applied by a nurse who was not involved with subsequent assessment"
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "seventy‐two patients were recruited into the trial but five were later withdrawn: two patients had problems with the PCA (one severe itching, one was unable to operate it) and both were converted to intramuscular analgesia, one patient was inadequately followed up, one patch was accidentally removed and one patient developed an allergy to the dressing. Of the remaining 67 subjects, 37 were in the active group and 30 in the placebo group"
Selective reporting (reporting bias)	Unclear risk	Judgement comment: no reference to 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