Introduction : Dextromethorphan, an antitussive agent, is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist which binds to receptor sites in the spinal cord and central nervous system, thereby blocking the generation of central pain sensations arising from peripheral nociceptive stimuli and enabling reduction in the amount of analgesics required for pain control. Studies have found that dextromethorphan attenuates the sensation of pain at doses of 30-90 mg without major side effects. Objective : To evaluate the effects of oral dextromethorphan (60 mg) on postoperative pain aftertotal abdominal hysterectomy Design : A double-blind randomized controlled trial. Materials and Methods : One hundred patients, ASA class I-II, age 18-65 years, scheduled for elective total abdominal hysterectomy under general anesthesia, were randomized to receive oral dextromethorphan 60 mg or a placebo at 1 hour before surgery. Following surgery, the patients then received patient-controlled analgesia with morphine for 48 hours postoperative as an analgesic. The dextromethorphan and placebo groups were compared in terms of total morphine consumption and pain scores (verbal numerical rating scales ; VNRS) hours postoperative. Results : There was no significant difference between dextromethorphan and placebo groups in terms of total morphine consumption at 48 hours. [32 (19-42.5) and 38 (21.5-46.25) : of the dextromethorphan group were significantly lower than the placebo group at every time of the study. Conclusion : Premedication with oral dextromethorphan 60 mg reduces the VNRS but does not reduce postoperative analgesic consumption after total abdominal hysterectomy.