Zhou 2001.

Methods	Randomized, double‐blinded, double‐dummy, placebo‐ and active‐controlled Medication administered on postoperative day 1 when baseline pain reached moderate‐to‐severe intensity
Participants	Type of surgery: orthopedic Propacetamol group Entered/completing: 60/57 Age (mean, SD): 61.4 ± 12.0 Sex (male, %): 37 Ketorolac group Entered/completing: 28/27 Age (mean, SD): 60.6 ± 11.1 Sex (male, %): 22 Placebo group Entered/completing: 55/52 Age (mean, SD): 60.9 ± 12.4 Sex (male, %): 40
Interventions	Intervention: 2 g propacetamol over 15 min Control: 15 mg ketorolac (not included in our analysis) Control: 30 mg ketorolac Placebo: saline
Outcomes	Time to onset of and number of patients experiencing analgesia (double‐stopwatch method) Pain intensity at rest and with activity (VRS, VAS) and derived summary measures Pain relief (categorical) and derived summary measures Time to, number of patients requesting, and consumption of rescue medication (morphine via PCA) Global evaluation (categorical)
Source of funding	Supported in part by a grant from UPSA Inc., France, and in part by the White Mountain Institute (a non–for profit public charity) in Los Altos, CA
Were treatment groups comparable at baseline?	Yes: demographic, anesthetic and surgical characteristics
Details of preoperative pain	Not reported
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated schedule
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	All study medication solutions prepared by a hospital pharmacist who was not involved in the data collection. Double‐dummy technique employed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Although 172 patients were initially randomized into the study groups, 164 received the study medication and were included in the intention‐to‐treat analysis
Selective reporting (reporting bias)	Low risk	Free of selective reporting. All outcomes from Methods section reported in Results section.
Size	Unclear risk	50 to 199 participants per arm of the study (60 propacetamol, 28 ketorolac, 55 placebo)

AE = adverse event; ASA = American Society of Anesthesiologists physical status classification system; AUC = area under the curve; BMI: body mass index; BOCF = baseline observation carried forward; BP = blood pressure; DSST = digit symbol substitution test; h = hour; HR = heart rate; ICU = intensive care unit; IM = intramuscular; INR = international normalized ratio; IQR = interquartile range; ITT = intention‐to‐treat; IV = intravenous; LA = local anesthetic; LOCF = last observation carried forward; min = minutes; NRS = numerical rating scale; NS = normal saline; N/V = nausea/vomiting; OR = operating room; PACU = post anesthesia care unit; PCA = patient‐controlled analgesia; PI = pain intensity; PT = prothrombin time; SD = standard deviation; SPID = summed pain intensity difference; TDT = Trieger dot test; THA = total hip arthroplasty; TOTPAR = total pain relief; VAS = visual analog scale; VPS = verbal pain score; VRS = verbal rating scale; WOCF = worst observation carried forward.