Clinical Application of the Muscle-Relaxant Effects of Magnesium in Anaesthesia: Data from Randomized Trials and Meta-Analysis

Background and Objectives: Magnesium sulfate (MgSO₄) has gained increasing attention in anaesthesiology due to its analgesic, muscle-relaxant, and hemodynamic-stabilizing properties. Acting as a calcium channel antagonist, magnesium reduces presynaptic acetylcholine release and potentiates the effects of neuromuscular blocking agents. The aim of this review is to evaluate the clinical role of intravenous magnesium sulfate as an adjuvant for enhancing neuromuscular blockade (NMB) during general anesthesia based on a summary of the available data. Materials and Methods: A narrative review of the literature was conducted, including clinical studies published between 1978 and 2025. The analysis comprised 18 randomized controlled trials (RCTs), 1 systematic review with meta-analysis, and 1 retrospective population-based cohort study. The included studies evaluated the interaction between MgSO₄ and depolarizing or non-depolarizing neuromuscular blocking agents in adult patients undergoing general anesthesia. Outcomes of interest included onset, duration, recovery of neuromuscular block, intubation conditions, required relaxant dose, effects during rapid sequence induction, and safety. Results: The majority of randomized trials demonstrate that magnesium sulfate accelerates the onset and prolongs the duration of neuromuscular blockade induced by non-depolarizing agents. Some clinical studies reported improved intubation conditions and reduced relaxant dose requirements. Data regarding recovery and reversal of neuromuscular block are heterogeneous. Magnesium pretreatment was associated with reduced fasciculations, myalgia, and potassium release after succinylcholine (SCh). The reviewed studies reported no serious adverse events or clinically significant hemodynamic instability at doses of 30–60 mg/kg. Conclusions: Intravenous magnesium sulfate is a valuable pharmacological adjuvant in anesthesia, enhancing neuromuscular blockade and improving intubation conditions while allowing dose reduction of neuromuscular blockers. Its use requires strict quantitative monitoring of neuromuscular transmission (NMT). Future large-scale, standardized trials should define optimal dosing strategies and long-term safety.