Adjunctive Intravenous Magnesium Sulfate for Postoperative Pain and Opioid Reduction in Lower Extremity Orthopedic Surgery: A Double-Blind Randomized Controlled Trial

Background/Objectives: Postoperative pain in lower extremity orthopedic surgery remains inadequately controlled. Magnesium sulfate may serve as an effective adjunct to reduce pain and opioid use. To evaluate the efficacy and safety of intravenous magnesium sulfate (30 mg/kg) as an adjuvant to ketorolac. Methods: Randomized, double-blind, placebo-controlled, parallel-group superiority trial. Sixty adult patients undergoing elective lower limb orthopedic surgery were randomized (1:1) to receive either intravenous magnesium sulfate (30 mg/kg) or placebo over 60 min before surgery. All patients received standard anesthesia and postoperative ketorolac with morphine PCA. The primary outcomes were postoperative pain (VAS) and morphine consumption over 24 h. Secondary outcomes included time to first analgesic request, serum magnesium levels, and adverse events. Allocation was concealed via opaque envelopes, and blinding was maintained for participants, clinicians, assessors, and analysts. Results: All 60 patients completed the trial. The magnesium group showed significantly lower VAS scores and reduced 24 h morphine use (median 6 mg vs. 8 mg, p < 0.001), with longer time to first analgesic request (540 vs. 300 min, p < 0.001). Four patients (13%) in the magnesium group had transient hypotension; no serious adverse events occurred. Conclusions: Low-dose intravenous magnesium sulfate safely reduced pain and opioid needs in orthopedic surgery and may be considered in multimodal analgesia strategies.