Van Aken 2004.

Methods	Randomized, double‐blinded, double‐dummy, placebo‐ and active‐controlled Medication administered when baseline pain reached moderate‐to‐severe intensity within 3 h after regaining consciousness
Participants	Type of surgery: dental Propacetamol group Entered/completing: 31/31 Age (mean, SD): 20.0 ± 4.9 Sex (male, %): 25 Morphine group Entered/completing: 30/30 Age (mean, SD): 18.8 ± 4.3 Sex (male, %): 39 Placebo group Entered/completing: 34/34 Age (mean, SD): 20.9 ± 6.6 Sex (male, %): 29
Interventions	Intervention: 2 g propacetamol in 150 ml normal saline over 15 min Control: 10 mg morphine Placebo: 150 ml normal saline
Outcomes	Pain intensity (VRS, VAS) and derived summary measures Pain relief (VRS) Proportion of patients requesting and time to rescue medication (morphine) Global assessment (at 10 h)
Source of funding	Supported by a grant from Bristol‐Myers Squibb
Were treatment groups comparable at baseline?	Yes: demographics, duration of surgery, baseline pain intensity No: the morphine group had a larger proportion of ASA II participants than the placebo group (P value < 0.01)
Details of preoperative pain	Not reported
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	Double‐dummy technique employed
Incomplete outcome data (attrition bias) All outcomes	Low risk	From 99 patients 4 were excluded due to protocol violations before any data had been collected. "All 95 remaining patients from whom efficacy data were obtained were included in the efficacy analysis".
Selective reporting (reporting bias)	Unclear risk	All outcome from Methods section reported in Results section
Size	High risk	Fewer than 50 participants per arm of the study (31 propacetamol, 30 morphine, 34 placebo)