Inhaled magnesium sulfate in the treatment of acute asthma.

Systematic review and meta-analysis of randomized trials in adults and children with acute asthma exacerbations treated in acute care settings, usually emergency departments. Most participants had moderate to severe or life-threatening asthma; one study enrolled only pregnant women and was not pooled in the meta-analyses.

Nebulized magnesium sulfate was administered by inhalation, most often as an adjunct to inhaled salbutamol with or without ipratropium bromide, and in some trials as magnesium sulfate alone versus inhaled beta-agonist. Doses varied across studies, ranging from a single nebulized treatment to 3 or 4 doses given about 20 minutes apart; examples included 2 mmol in 7.5 mL saline, 3 mL of 10% isotonic solution, or 384 mg every 20 minutes for 3 doses.

Nebulized magnesium sulfate may provide modest short-term improvements in lung function and may slightly reduce admission when added to inhaled beta-agonists and ipratropium, but the overall evidence is low certainty and larger trials generally did not show clinically important benefit. In pooled analyses, admission with MgSO4 + SABA + ipratropium was RR 0.95, 95% CI 0.91 to 1.00, and % predicted FEV1 with MgSO4 + SABA was MD 3.34, 95% CI -1.58 to 8.26. Small-study signals favored magnesium for some spirometry outcomes, including a pooled MD 3.28, 95% CI 1.06 to 5.49 in two smaller studies, but other larger analyses were null. Serious adverse events were not increased overall.

Confidence in the evidence was low, with substantial heterogeneity, variable dosing and comparators, and inconsistent outcome reporting across trials. Several analyses relied on small studies or single trials, many outcomes could not be pooled, and larger multicenter trials generally found no clinically important benefit. Generalizability is limited by mixed adult and pediatric populations and one pregnant-women study that was not pooled.