Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 58 5 2020 08 10 221 224 Farhad Etezadi Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Mansour Farzizadeh Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran. Hamid Reza Sharifinia Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Maysam Alimohammadi Department of Neurosurgery, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran Mohammad Reza Khajavi Department of Anesthesiology, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran 2019 12 08 2020 05 04 Ketamine and magnesium in brain act as an N-methyl-D-aspartate receptor antagonist that has been shown to be useful in the reduction of acute postoperative pain and analgesic consumption in a variety of surgical interventions. We hypothesized that combination of low dose ketamine and magnesium would reduce early postoperative opiate consumption and analgesic requirement after 6 weeks. This was a randomized, prospective, controlled-placebo trial involving elective and eligible patients undergoing lumbar spine surgery. Seventy patients in the treatment group were administered 0.5 mg/kg intravenous ketamine and 1 gram of magnesium as an intravenous bolus slowly during 3 minute before incision and 0.25 mg/kg/hr ketamine and 0,5 g/hr magnesium intravenous infusion during surgery. Seventy patients in the placebo group received saline of equivalent volume. Patients were observed for48 h postoperatively and followed up at 6 weeks. The primary outcome was 48h morphine consumption. The severity of pain was lower in the intervention group than in the placebo group during 48 hr post-operatively, morphine consumption in this group also decreased significantly during this period. Intraoperative ketamine-magnesium reduces opiate consumption in the 48-h postoperative period. This combination may also reduce pain intensity throughout the postoperative period in this patient population. https://acta.tums.ac.ir/index.php/acta/article/view/8212 https://acta.tums.ac.ir/index.php/acta/article/download/8212/5402