Tehran University of Medical Sciences Archives of Anesthesiology and Critical Care 2423-5849 0 0 2026 01 01 1373 1373 Seyedbabak Mojaveraghili Department of Anesthesiology & Intensive Care, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran. Mohammadali Izadfar Department of Neurological Surgery, Faculty of Medicine, Golestan University of Medical Sciences, Gorgan, Iran. Naser Behnampour Health Management and Social Development Research Centre, Department of Biostatistics and Epidemiology, Golestan University of Medical Sciences, Gorgan, Iran. 2025 08 07 2025 08 13 Background: Spinal fusion surgery, as one of the treatment options for back pain, often results in significant postoperative pain due to complexity and multiple incisions. Glutamate receptors such as NMDA are among the main receptors involved in this process, causing central hyperalgesia and sensitization and ultimately accelerating pain processing in the CNS. Therefore, NMDA receptor antagonists such as ketamine and magnesium sulfate can be considered as suitable options for treating pain caused by these surgeries. A prospective study was conducted to compare the effects of ketamine and magnesium sulfate on pain control in these patients. This double-blind clinical trial was performed on 72 patients undergoing fusion surgery, referred to the 5th Azar Medical & Educational Center of Gorgan in 2020-2022. Methods: In group A, 50mg/kg of magnesium sulfate along with CVE=5 ml/kg was infused over 20 minutes, and then 500 mg/h of magnesium sulfate was given during and up to 48 hours after surgery. In group B, 0.5 mg/kg of ketamine was given as a bolus after patient positioning and 2 minutes before surgical incision, followed by 2.5 mcg/kg/h of ketamine during and up to 48 hours after surgery. Pain was evaluated using the NRS scale from admission to recovery up to 48 hours after surgery, and the amount of opioid consumption was recorded. Results: Both ketamine and magnesium sulfate led to a significant reduction in pain during the first 48 hours after surgery (P value <0.0001). The speed of pain reduction in the first 6 hours was higher in women in the ketamine group and in men in the magnesium group, although the results were reversed in the second 6 hours. Pain assessment in opium addicts indicated the superiority of magnesium in the speed of pain reduction in patients during the first 12 hours. The amount of analgesic used during recovery was statistically similar in both groups (p=0.645), but during the 24 hours after surgery, the amount of opioid consumption used in the magnesium group was significantly lower (p=0.025). After 24 hours, none of the two groups needed analgesics. No severe side effects were observed in any of the patients in the two groups. Conclusion: Magnesium sulfate not only works well with ketamine in controlling postoperative pain but can also perform better than ketamine in women and opioid addicts, leading to a reduction in the use of opioids and avoidance of ketamine's side effects. In addition to reducing pain and analgesic use, considering the benefits of magnesium in stabilizing hemodynamics and reducing anesthetic use, this drug can be a very suitable alternative to ketamine for a wider range of patients undergoing spinal surgery, including those with heart and mental illnesses. https://aacc.tums.ac.ir/index.php/aacc/article/view/1373