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

The analgesic benefit of melatonin and vitamin C as primary or adjuvant agents has been reported in various studies; however, their analgesiceffects in the treatment of postoperative pain remain unclear. Thus, we aimed to evaluate the effect of preoperative single dose of oral melatonin and vitamin C administration on postoperative analgesia. One hundred sixty-five adult patients undergoing elective major abdominal surgery with general anesthesia were recruited in this study. Patients were randomly divided intothreeequal (n=55) groups. One hour before surgery, patients received melatonin (6 mg) in group M, vitamin C (2 g) in group C or a placebo tablet in group P, orally. Pain, sedation, patient satisfaction,total morphine consumption from a patient-controlled analgesia device, supplement analgesic requirement, and the incidence of nausea and vomitingwere recorded throughout 24 h after surgery.After analyzing the data, meanpain scores andtotalmorphine consumptions werefound significantly lower inbothgroup M and C comparedwith group P (p<0.001). There were nosignificant differences between group M and C with respect to pain scores (p=0.117) andtotalmorphine consumptions (p=0.090). Patients requested less supplement analgesic and experienced less nausea and vomiting in group M and C compared with group P. In conclusion, preoperativeoral administrationof both 6 mgmelatoninand 2 g vitaminC led to a reduction in pain scores, total morphine consumption, supplement analgesic requirement, and the incidence of nausea and vomiting compared with placebo.