Coli 1993.

Study characteristics
Methods	Study design: parallel‐group randomized controlled trial Sample size: 50 Country: Italy Setting: secondary care Dates conducted: not reported Postoperative opioid used and delivery: buprenorphine Pain score collection: not included as outcome Concurrent postoperative analgesics: none reported
Participants	Inclusion criteria ASA 1 or 2 Weighing between 50 and 90 kg Lumbar laminectomy Exclusion criteria Aged < 18 and > 65 years old Diabetes Gastroduodenal ulcer Alcoholism Allergic to study medications Psychiatric disorders Renal and hepatic impairment Anticoagulants or antiplatelets Calcium channel blockers, beta‐blockers or angiotensin‐converting enzyme inhibitors Clonidine Psychotropic drugs NSAIDs in the 12 hours pre‐intervention
Interventions	Group I (25 participants): IV sodium naproxen 550 mg immediately after induction of anaesthesia Group II (25 participants): IV sodium naproxen 550 mg at the end of surgery
Outcomes	Analgesic consumption (mg of buprenorphine consumed at 24 hours) Time to analgesic request (hours)
Notes	Funding: not reported Declarations of interest: not reported Authors contacted: no Other: article in Italian so translated. Buprenorphine consumption converted to mg intravenous morphine. Standard deviations estimated. Time to analgesic request data extracted from graph
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details
Allocation concealment (selection bias)	Unclear risk	No mention
Blinding of participants and personnel (performance bias) All outcomes	High risk	No double‐dummy placebo. Quote: "group I received Naproxen sodium 550 mg intravenously immediately after induction of anesthesia; group II received sodium naproxen 550 mg intravenously at the beginning of the surgical suture".
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No mention
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants analysed
Selective reporting (reporting bias)	Unclear risk	No protocol or trial registration
Other bias	Low risk	Similar baseline characteristics. Quote: "The three groups were comparative to the distribution by age, weight, sex and duration of the intervention".