Mendl 1992

Methods	Randomised, double blind, active control (tramadol), single IV dose. Study duration 4 h Baseline PI = severe Self assessment at t = 0.15, 0.30, 1, then hourly up to 4 h.
Participants	Abdominal or urinary tract surgery N = 100 M/F not reported Age 18‐65 years
Interventions	Dipyrone 2.5 g IV, n = 50 Tramadol 100 mg IV, n = 50
Outcomes	PI: VAS ‐ verbal pain rating scale (undefined) PR: 100 mm VAS (no relief‐complete relief) Adverse events
Notes	Oxford Quality Score: R1, DB1, W0. Total = 2
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not reported