Oreskovic 2014.

Methods	Double‐blind, randomized, active‐controlled, parallel‐group study with intervention at end of surgery x 24 h for outcomes
Participants	Type of surgery: total hip arthroplasty under spinal anesthesia Paracetamol group Entered/completing: 43/43 Age (mean, SD): 57.7 (13.8) Sex (male, %): 39.5 Metamizol group Entered/completing:51/51 Age (mean, SD): 62.2 (12.4) Sex (male, %):29.4 All: morphine PCA at baseline
Interventions	Paracetamol: IV 1 g paracetamol every 8 h x 24 h, start at ICU admission Metamizol: IV 1.5 g every 8h x 24 h, start at ICU admission All: PCA morphine with continuous setting 1 to 2 mg/h (based on participant weight), 1 mg bolus with 15 min lockout x 24 h
Outcomes	Primary: pain intensity in the first 24 h after surgery. Total pain over the study period was calculated as area under the pain/time curve. VAS 0 to 100 with a 10 cm ruler. Secondary: pain was assessed at time points of 1, 2, 3, 4, 6, 8, 10, 14, 18 and 22 h post‐baseline Amount of morphine consumption in 24 h
Source of funding	No financial support
Were treatment groups comparable at baseline?	Yes: demographics, estimated blood loss, duration of surgery
Details of preoperative pain	None
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomly generated list
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding (performance bias and detection bias) All outcomes	Low risk	“Research team and the patients were not familiar with the information about products that patients received. Drugs were prescribed by an independent doctor and administered by nurses not involved in the research. Nurses not involved in the research recorded VAS scale results. Independent blinded researchers performed clinical observations”.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All randomized participants completed study. No mention of how missing data were imputed.
Selective reporting (reporting bias)	High risk	No reporting of adverse events
Size	High risk	Fewer than 50 participants per arm of the study (43 paracetamol, 51 metamizol)