Allopurinol attenuates postoperative pain and modulates the purinergic system in patients undergoing abdominal hysterectomy: a randomized controlled trial

Purpose Allopurinol is a potent inhibitor of the enzyme xanthine oxidase used primarily in the treatment of hyperuricemia and gout. The aim of this study was to compare the analgesic efficacy of preanesthetic allopurinol versus placebo on postoperative pain and anxiety in patients undergoing abdominal hysterectomy. Methods This is a prospective, double-blinded, placebo-controlled, randomized clinical trial. We investigated 54 patients scheduled to undergo elective abdominal hysterectomy. Patients were randomly assigned to receive either oral allopurinol 300 mg ( n = 27) or placebo ( n = 27) the night before and 1 h before surgery. Patients were submitted to evaluation of pain and anxiety before the treatment, for 24 h postoperatively, 30 and 90 days after surgery. Cerebrospinal fluid was collected at the time of the spinal anesthesia to perform the measurement of the central levels of purines. Results Preoperative administration of allopurinol was effective in reducing postoperative pain 2 h after surgery. Allopurinol caused a reduction of approximately 40% in pain scores measured by the visual analogue pain scale after surgery ( p