Magnesium sulfate is used as an anesthetic adjuvant during general anesthesia. This drug interacts with neuromuscular blocking agents, but results from existing clinical trials that assessed this interaction are contradictory.

To evaluate the influence of magnesium sulfate in the pharmacodynamics of neuromuscular blockers during general anesthesia.

A systematic review and meta-analysis of randomized controlled trials.

An electronic bibliography search was conducted through MEDLINE and the Cochrane Central Register of Controlled Trials since 2015.

Randomized, double-blind clinical trials relating to general anesthesia in elective surgery using intravenous magnesium sulfate, and reporting information on the pharmacodynamics of neuromuscular blocking in American Society of Anesthesiologists categories I and II patients.

Twelve clinical trials that evaluated the pharmacodynamics of neuromuscular blocking during general anesthesia were selected. All of them assessed the “onset time” variable, and according to the standardized mean difference they report, which was −1.09, 95% confidence interval (CI)(−1.53, −0.66), and P<.001, they concluded that magnesium shortens the onset time of neuromuscular blockade. Eight of the trials measured “clinical duration” as a variable of study and observed a standardized mean difference of 1.88 minutes, 95% CI (1.13, 2.63), and P<.001 in favor of the notion that the placebo group presents a shorter time effect. Five studies checked for the “recovery index” as a variable of study and found a significant standardized mean difference of 1.42, 95% CI (0.41, 2.43) with P=.006 toward the placebo group, indicating a faster recovery in this group.

The administration of magnesium sulfate during the perioperative period alters neuromuscular blockade pharmacodynamics causing a shortening of the onset time, prolongs the clinical duration, and improves the recovery time of these drugs.