During the surgical procedure of scoliosis correction via trans-thoracic approach, surgery extent and long-lasting strong nociceptive stimulation lead to postoperative pain formation of greater intensity compared with other orthopaedic interventions. Developing neuroplastic changes in the central nervous system may lead to persistent pain formation despite proper tissue healing. The NMDA receptor accounts for the central sensitization phenomenon caused by increased stimulation.The aim of the undertaken clinical study was to evaluate the influence of two chosen drugs: amantadine and dextro-metorphan, on the postoperative pain therapy. The study included 90 patients, divided randomly into three study groups A, D and P. The main analgesic used in postoperative pain therapy was morphine administered intrave-nously. The observation period included three postoperative days. The influence of administered drugs on: postoperative pain using the NSR score, re-quirement for opioid analgesics during intervention and postoperatively, time of first dose of „on demand” analgesics, presence of adverse drug reaction, morphine, M3G and M6G concentration in the serum, basic hemodynamic parameters, subjective evaluation of analgesic therapy were evaluated. Pain intensity using the NRS scale was lower in group A compared to group P, the differences were statistically significant. Pain intensity in group D was statistically lower during the first four hours of observation compared to group P. Analyzing the demand on phentanyl, it was statistically lower in group A and significantly lower in group D compared to group P. The requirement on morphine during the first postoperative day was statistically lower in group A compared to group P and group D. A 25% reduction of morphine intake was noted in group A in the first two postoperative days compared to the control group. In group D also a reduction of 10% was noted. The time of first „on de-mand” postoperative analgesic was statistically lower in group A compared to group D and group P. Above that lower intensity of sedation and nausea was noted in groups A and D compared to group P. Patients evaluated their analgesic therapy as good. The observations obtained in this study support the fact that co-administration of non-competitive antagonists of the NMDA receptor in the treatment of postoperative pain increases the analgesic effect of routinely used opioid drugs.