Comparison of effects of preoperative melatonin or vitamin C administration on postoperative analgesia

Aim: We aimed to determine the effect of preoperative oral melatonin and vitamin C administration on postoperative analgesia in ASA I-II patients between 18-65 years of age, undergoing elective major abdominal surgery. Methods: One hundred-sixty five ASA I-II adult patients undergoing elective major abdominal surgery with general anesthesia were included in this placebo-controlled, randomized, double-blind study. Patients were randomly divided into three groups. Oral 6 mg melatonin tablet was given 1 hour before surgery preoperatively to the first group (Group M, n = 55), oral 2 g Vitamin C tablet was given 1 hour before surgery preoperatively to the second group (Group C, n = 55), and oral placebo tablet was given 1 hour before surgery preoperatively to the third group (Group P, n = 55), and standard anesthetic protocol was administered to all patients. At the end of surgery, postoperative pain control was provided via a patient controlled analgesia (PCA) device incluiding morphine for all patients in all groups. Starting from perioperative period, during 24 hours hemodynamic parameters, visual analog scale, nausea / vomiting scores, sedation, pruritus, hypotension, bradycardia, other side effects such as allergic reactions and patient satisfaction scales and dose and number of morphine amounts demanded and given from PCA device were recorded for all patients. Results: 24 hours total VAS scores were significantly lower in the melatonin and vitamin C groups compared to placebo (p <0.001; total VAS for melatonin: 32.5 ± 4.45, vitamin C: 34.8 ± 0.72, placebo: 42.7 ± 8.13), there was no significant difference between melatonin and vitamin C groups (p = 0.117). Total amount of analgesia demanded from PCA device was found significantly lower in melatonin and vitamin C groups compared to placebo (p <0.001, respectively, 22.3 ± 13.7, 27.2 ± 10.6, 33.7 ± 14.4), and there was no significant difference between vitamin C and melatonin groups (p = 0.114). Total consumption of analgesia was found significantly lower in melatonin and vitamin C groups compared to placebo (p <0.001, respectively, 13.3 ± 4.7, 15.1 ± 4.0, 18.0 ± 1.0), there was no significant difference between melatonin and vitamin C groups (p = 0.090). Side effects such as nausea / vomiting, bradycardia, hypotension, itching were less; patient satisfaction was better; additional analgesia requirements were less in melatonin and vitamin C groups. Sedation scores were higher in the group receiving melatonin for the postoperative first 30 minutes, after postoperative 1 hour sedation scores were higher in placebo group which has higher analgesic consumption amount. Statistically significant difference was found between groups in terms of recovery time (p = 0.019, respectively, 4.4 ± 1.6, 3.6 ± 1.6, 4.0 ± 2.6). Conclusion: With preoperative oral administration of 6 mg melatonin or 2 g vitamin C one hour before surgery, VAS scores and analgesic consumption may be decrased and fewer side effects in postoperative analgesia may be achieved.