The Effect of Preoperative Sublingual Melatonin on Postoperative Pain Severity in Patients Undergoing Colorectal Surgery: A Triple-Blinded Randomized Trial

Background: Postoperative pain has detrimental physiologic and psychologic effects on patients’ outcomes, such as increased postoperative morbidity, delayed recovery, and reduced patient satisfaction. This study aimed to determine the effect of preoperative sublingual melatonin on pain severity after colorectal surgery. Methods: We performed a randomized, placebo-controlled, triple-blinded study to test the efficacy of 6 mg of sublingual melatonin or placebo 1 hour preoperative on pain severity and sedation of 60 patients after colorectal surgeries. Pain and sedation were assessed by numerical verbal response (NVR) and the Ramsey sedation score, respectively, at the baseline, 1, 2, 6, 12, and 24 hours after surgery. The repeated measures analysis of variance was used to assess group × time interaction, and the Bonferroni adjustment was used for between-group comparisons. Results: A total of 60 patients with a mean ± SD age of 49.35 years were equally randomized to the study groups. There was no significant difference between groups with respect to the baseline characteristics. The mean score of pain severity of patients in the melatonin group was significantly lower compared with the placebo group at 2, 6, 12, and 24 hours after surgery. The total mean pain score for the first 12 hours (mean difference [MD] [SE], 0.41 [0.12]; 95% CI, 0.17-0.65; [P = 0.012]) and the mean score of pain in 24 hours after surgery were significantly lower in the melatonin group in comparison with the placebo group (MD [SE], 0.44 [0.13]; 95% CI, 0.19-0.69; [P = 0.001]). Compared with the placebo group, the percent of patients who were cooperative, aware, and calm was significantly higher in the melatonin group at the baseline (43.3% vs 53.3%) and at 1 (36.7% vs 60%) and 2 hours (33.3% vs 80%). Conclusion: The use of 6 mg preoperative melatonin sublingual tablet in patients with colorectal surgeries could reduce the severity of postoperative pain, patients’ restlessness and anxiety, and increase patients' cooperation and calmness. Therefore, it seems that sublingual melatonin is an effective drug in controlling postoperative pain.