Maghsoudi 2014.

Methods	Randomized, double‐blind, placebo‐controlled multiple dose, 24‐hour study Medication was administered 30 min after extubation
Participants	Type of surgery: percutaneous nephrolithotomy Paracetamol group Entered/completing: 50/50 Age (mean, SD): 44.48 +/‐ 12.92 Sex (male, %): 34 (68%) Placebo group Entered/completing: 50/50 Age (mean, SD): 42.56 +/‐ 13.57 Sex (male, %): 40 (80%)
Interventions	Paracetamol: 100 ml normal saline and 1 g paracetamol IV 30 min after extubation and every 8 h until 24 h (4 g total) 100 ml IV normal saline 30 min after extubation and every 8 h until 24 h
Outcomes	Primary: pain intensity (VAS) over first 6 h and 24 h after extubation, demand for opioid analgesia (pethidine 25 to 50 mg IM up to 200 mg per day), total pethidine dose consumed Secondary: adverse effects
Source of funding	Not mentioned
Were treatment groups comparable at baseline?	Yes ‐ age, BMI, stone size, operative time, baseline VAS. No mention if # of males balanced – 40 versus 34.
Details of preoperative pain	Participants were excluded if they reported use of a NSAID or other analgesic less than 12 h before prescribing the study medications. Also excluded if painful physical conditions that may affect pain assessment after percutaneous nephrolithotomy
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Balanced blocked randomization; randomization schedule was prepared by someone that was blinded to the study.
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Low risk	“Serums containing placebo and paracetamol, identical in color and appearance were prepared by an assistant and administered by nursing personnel blinded to the study.” Other group blinded was not specifically stated but assumed to be participants.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Per Results, 2 participants did not complete the study but no additional information was provided. No deviations from the protocol was also noted.
Selective reporting (reporting bias)	Low risk	Frequency of VAS < or > 4 was not mentioned as an outcome in Methods (Table 2)
Size	Unclear risk	50 to 199 participants per arm of the study (50 paracetamol, 50 placebo)