Naguib 1999

Methods	Randomized, double‐blind, placebo‐controlled study Location: Saudi Arabia Study design: parallel, 3‐armed
Participants	A total of 75 patients randomized 75 patients completed: 25 in melatonin group, 25 in placebo group, 25 in midazolam group Age: melatonin 29.6 (22 to 43), placebo 30.1 (22 to 40), midazolam 29.5 (19 to 44) Gender (M/F) in %: melatonin (0/100), placebo (0/100), midazolam (0/100) ASA class: I Type of surgery: gynaecological laparoscopic procedures Type of anaesthesia: general Baseline (anxiety, pain) described: yes, no
Interventions	Melatonin: 5 mg Placebo: saline Midazolam: 15 mg Administration route: sublingual Time of administration: approximately 100 min preoperatively
Outcomes	1. Anxiety assessed by Visual Analogue Scale (0 to 100) (pre‐ and postoperative) 2. Orientation score (0 to 2) 3. Sedation score (0 to 4) 4. Psychomotor activity measured by The Digit‐symbol Substitution Test and Trieger dot test 5. Amnesia by showing line diagrams 6. Postoperative pain assessed by Visual Analogue Scale (0 to 100) and morphine consumption (mg)
Notes	Sample size calculation: described Author contacted by e‐mail on 9 August 2013 to clarify unspecified issues ‐ e‐mail returned = delivery failure
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "... allocated randomly..." (page 876) (Naguib 1999)
Allocation concealment (selection bias)	Unclear risk	No information provided
Incomplete outcome data (attrition bias) All outcomes	Low risk	No reported dropouts or missing data
Selective reporting (reporting bias)	Unclear risk	Study protocol not available
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "... marked only with a coded label to maintain the double‐blind nature of the study" (page 876)
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "The same psychologist blinded to group assignment performed all test scoring and calculations" (page 876)