Effect of Intravenous Magnesium on Postoperative Pain and Analgesic Outcomes in Patients Undergoing General...

Background: Intravenous magnesium sulfate has been proposed as an adjuvant analgesic in perioperative care; however, its effects on postoperative pain and related analgesic outcomes remain uncertain. Methods: A systematic search of the literature was conducted from 1 January 2015 through 19 January 2026 to identify randomized controlled trials comparing intravenous magnesium sulfate with placebo in adults undergoing general anesthesia. Pain intensity was harmonized to a 0-10 scale. Primary outcomes were early postoperative pain (0-6 h), pain at 12 h, and pain at 24 h. Secondary outcomes were postoperative opioid consumption, expressed as intravenous morphine equivalents, and time to first rescue analgesia. Random-effects meta-analyses were performed. Risk of bias was assessed using RoB 2, and certainty of evidence using GRADE. Results: A total of 24 randomized controlled trials were included in the qualitative synthesis, of which 22 provided data for quantitative meta-analysis, yielding 23 comparisons and a total of 1750 participants. Intravenous magnesium reduced early postoperative pain (mean difference [MD] -0.90, 95% confidence interval [CI] -1.33 to -0.47; I² = 96.27%) and pain at 24 h (MD -0.59, 95% CI -1.00 to -0.18; I² = 66.36%), but not pain at 12 h (MD -0.52, 95% CI -1.15 to 0.11; I² = 77.38%). Magnesium also reduced postoperative opioid consumption (MD -6.28 mg morphine equivalents, 95% CI -8.94 to -3.61; I² = 95.93%) and prolonged time to first rescue analgesia (MD 85.61 min, 95% CI 40.11 to 131.10; I² = 79.37%). Certainty of evidence ranged from very low to moderate, with the highest certainty observed for pain at 24 h. Conclusions: Intravenous magnesium was associated with reduced postoperative pain, particularly at 24 h, and with opioid-sparing effects. However, substantial heterogeneity across outcomes and generally low-to-moderate certainty of evidence warrant cautious interpretation. Magnesium may be considered as part of multimodal analgesia in appropriately selected patients.