Arslan 2013.

Methods	Randomized, placebo‐controlled, single dose, over 24 h Interventions administered preemptively (not included in this review) or at end of surgery
Participants	Type of surgery: elective lap cholecystectomy Paracetamol group Entered/completing: 100/100 Age (mean, SD): 41.5 ± 7.8 Sex (male, %): 32 Control group Entered/completing: 100/100 Age (mean, SD): 44.5 ± 6.5 Sex (male, %): 34
Interventions	Paracetamol 1 g/100 ml IV over 10 min Placebo: saline as above
Outcomes	Primary: time to first rescue dose and cumulative amount of rescue analgesic (tramadol 100 mg IV for VAS pain score > 4, up to 400 mg max) Secondary: VAS pain scores at several time points up to 24 h, numbers of participants in each group requiring rescue medication within various postoperative intervals and cumulatively, adverse events, patient satisfaction at 24 h (0 = poor to 4 = excellent)
Source of funding	No funding
Were treatment groups comparable at baseline?	Yes
Details of preoperative pain	None – participants with history of usage of paracetamol, opioids, or NSAIDs for 3 months were excluded
Notes	Third group receiving paracetamol preemptively not included in this review. All participants received fentanyl 1 µg/kg at induction of anesthesia, which had a total duration of about 100 min in all groups.
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 mentioned
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	It appears that all participants completed the study and contributed data for each outcome at all relevant time points
Selective reporting (reporting bias)	Low risk	All outcomes from Methods section reported in Results section
Size	Unclear risk	50 to 199 participants per arm of the study (100 paracetamol, 100 placebo)