Kemppainen 2006.

Methods	Randomized, double‐blind, placebo‐controlled Medications administered at completion of surgery over 15 min
Participants	Type of surgery: endoscopic sinus Paracetamol group Entered/completing: 36/36 Age (mean, SD): not reported Sex (male, %): not reported Placebo group Entered/completing: 38/38 Age (mean, SD): not reported Sex (male, %): not reported
Interventions	Intervention: paracetamol 1 g IV Placebo: 100 ml normal saline
Outcomes	Pain intensity (NRS) Time to rescue medication Opioid consumption (oxycodone)
Source of funding	Not reported
Were treatment groups comparable at baseline?	No details
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 randomization
Allocation concealment (selection bias)	Low risk	Opaque envelope method
Blinding (performance bias and detection bias) All outcomes	Low risk	The nurse preparing the infusions did not participate in the study. Preparation of infusions of identical volumes (100 ml) to assure blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	"All the patients asked agreed to participate and there were no dropouts during the study".
Selective reporting (reporting bias)	Low risk	All outcomes from Methods section reported in Results section
Size	High risk	Fewer than 50 participants per arm of the study (36 paracetamol, 38 placebo)