The present study addressed the effect of melatonin premedication on propofol induction dose for anesthesia in abdominal surgery. This is a double-blinded clinical trial in which abdominal surgery patients admitted to the Valiasr Hospital, Iran (n = 88) were enrolled and individually randomized into two groups: melatonin and placebo groups sublingually administered 3 mg of melatonin and placebo, respectively, 50 minutes before surgery. Their anxiety, orientation, and sedation were recorded before melatonin administration, anesthesia induction, and recovery, while we also recorded the propofol induction dose required for general anesthesia. Anxiety was seen less in the melatonin group than the placebo group (P < 0.05), whereas orientation was significantly different before anesthesia induction (P = 0.044) and sedation was the same before the induction (P = 0.044) and recovery (P = 0.049) in both groups, with a better efficiency in the melatonin group in which a lower dose of propofol was used (P = 0.002). The sedation, anxiety, and propofol dose used were lower in the melatonin group than the placebo group. The recommended dosage was 3 mg of melatonin once to achieve an anesthetic depth index or a bispectral index of 40. The study was approved by Ethical Committee of Arak University of Medical Sciences with IR.ARAKMU.REC.1395.432 code in July 2016, and the trial was registered in Iranian Registry of Clinical Trials with IRCT20141209020258N98 in September 2016.
Keywords: abdominal surgery; anesthesia; induction; melatonin; premedication; propofol.