Beneficial Effect of Amantadine on Postoperative Pain Reduction and Consumption of Morphine in Patients Subjected to Elective Spine Surgery

Objective. To analyze the effect of coadministration of morphine and amantadine on postoperative pain reduction and morphine consumption in patients after elective spine surgery. Methods. In double-blinded study, 60 patients (ASA physical status I-II) were randomized into two groups. Group A was given oral amantadine 50 or 100 mg 1 hour before surgery and 8, 20, 32 hours after operation. Group P received placebo at identical times. Pain was assessed using numerical rating scale before first administration of morphine and in 2, 3, 4, 6, 24, and 48 hours after operation. The amounts of morphine consumed were recorded up to 48 hours after surgery. Blood samples were taken twice in 2 hours after surgery and plasma levels of morphine and its main metabolites were measured. Results. As compared with placebo, amantadine significantly reduced intra-operative Fentanyl use and sensation of postoperative pain. Up to 48 hours after operation, the cumulative consumption of morphine was 25% lower in the amantadine group. Moreover, intensity of nausea and vomiting tended to be lower in A group. Starting from 12th hour after surgery, the level of postoperative sedation was lower in patients who received amantadine, as compared with placebo group. No significant differences in plasma levels of morphine ant its metabolites were observed between A and P groups. Conclusions. Pre- and postoperative administration of amantadine significantly reduced fentanyl use during operation, as well as reduced the postoperative pain and decreased morphine consumption in young patients undergoing orthopedic surgery.