A Comparative Study of the Effect of Oral Dextromethorphan and Placebo on the Pain After Vitrectomy Surgery: A Double-Blind, Placebo-Controlled, Randomized Clinical Trial

Background: Postoperative pain is a major complication in patients undergoing eye surgery. N-methyl-D-aspartate (NMDA) receptor antagonists are widely used to manage postoperative pains. Dextromethorphan, as an NMDA antagonist, is commonly used as an oral drug. Objectives: This study was conducted to evaluate the effect of Dextromethorphan on post-operation pain and sedative effect in comparison to placebo. Methods: A double-blinded, placebo-controlled, randomized clinical trial, upon 60 patients undergoing vitrectomy surgery was done. Thirty patients received 30 mg oral Dextromethorphan before the operation, and 30 patients received a placebo. Post-operation pain and sedation were evaluated after zero, one, two, and six hours. Results: Post-operation pain was significantly lower in patients who received Dextromethorphan at zero, one, and two hours after operation (P < 0.001); however, not at six hours after operation (P = 0.11). Sedative effect was higher in the Dextromethorphan group at zero (P = 0.03) and one hour (P = 0.01) after operation. Conclusions: Prescribing oral Dextromethorphan before a vitrectomy surgery could reduce postoperative pain. It also has postoperative sedation effects.