Naguib 2006

Methods	Randomized, double‐blind, placebo‐controlled study Location: Saudi Arabia Study design: parallel, 2‐armed
Participants	A total of 200 patients randomized 200 patients completed: melatonin + propofol (MP) (50), melatonin + thiopental (MT) (50), placebo + propofol (PP) (50), placebo + thiopental (PT) (50) Age: MP (32.4 ± 19.9), MT (34.9 ± 8.9), PP (34.4 ± 8.9), PT (31.6 ± 10.9) Gender (M/F) in %: MP (52/48), MT (46/54), PP (30/70), PT (38/62) ASA class: I Type of surgery: not reported Type of anaesthesia: general Baseline (anxiety, pain) described: yes, no
Interventions	Melatonin (0.2 mg/kg) + propofol Melatonin (0.2 mg/kg) + thiopental Placebo + propofol Placebo + thiopental Placebo: saline Administration route: sublingual Time of administration: approximately 50 min preoperatively
Outcomes	1. Anxiety assessed by Visual Analogue Scale (0 to 100) (preoperative) 2. Orientation score (0 to 2) 3. Sedation score (0 to 4) 4. Induction of anaesthesia assessed by response to verbal command and eye‐lash reflex
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)	Low risk	Quote: "...according to a computer‐generated list" (page 1448) (Naguib 2006)
Allocation concealment (selection bias)	Low risk	Quote: "...according to a computer‐generated list" (page 1448)
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 1449) "The contents of the syringe was given sublingually...by a resident not involved in the management of the patient or in the data collection" (page 1449) "The attending anaesthesiologist was unaware of the premedication or induction medication used"
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "One investigator blinded to group assignment performed all test scoring in the perioperative period." (page 1449)