BackgroundPostoperative pain is a common problem in hospitals. Adults undergoing uvulopalatopharyngoplasty (UPPP) with tonsillectomy experience an unacceptable level of intense postoperative pain, especially during the first 24 h after surgery. This study investigated the analgesic effects of vitamin C in patients undergoing UPPP and tonsillectomy.MethodThis study was done on forty patients that were evaluated in a randomised double‐blinded clinical trial. Patients included in the study were within the age range of 25–50 years with BMI<35, physical status I,II according to the American Society of Anesthesia (ASA) and who underwent uvulopalatopharyngoplasty and tonsillectomy. Patients with epilepsy, BMI>35, any neuropsychiatric disorders, a history of chronic pain, liver and/or renal disease, drug allergy, and drug abuse were excluded from the study. All patients underwent the same method of anaesthesia and surgical procedure. During the first 30 min after the beginning of the surgery, group C (vitamin C) received infusion of 3 g vitamin C in 500 mL of Ringer and group P received 6 mL normal saline in 500 mL of Ringer. Measurements of systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and heart rate were recorded before and during anaesthesia and at intervals of 0,15,30 and 60 min after extubation. Pain severity was recorded according to VAS score at intervals of 0 (recovery room), 6, 12 and 24 h after the procedure, request for analgesic drugs (iv paracetamol or pethedine) according to total number of times of analgesic request and time of the first dose of analgesic use and dose of pethidine were also recorded by questionnaire.ResultsThere was a significant difference in evaluations for mean pain severity between the two groups at recovery room, 6, 12 and 24 h after surgery (P‐value = 0.001). There was a significant difference in mean times that patient requested an analgesic, time of first dose of analgesic and pethidine dose between the two groups (P‐value< 0.05). There was no significant differences in measurements of systolic blood pressure, diastolic blood pressure, mean arterial blood pressure and heart rate in different times between the two groups (P‐value> 0.05). Blood loss was similar in the two groups (P‐value> 0.05).ConclusionAccording to this study, administration of vitamin C 3 g IV intraoperative reduced postoperative pain without increased side‐effects in patients undergoing UPPP and tonsillectomy.