A Cochrane review included 7 studies (5 adult, 2 paediatric) with a total of 665 patients. Patients receiving magnesium sulfate demonstrated non-significant improvements in peak expiratory flow rates when all studies were pooled (weighted mean difference: 29.4 L/min; 95% confidence interval: -3.4 to 62). In studies of people with severe acute asthma, peak expiratory flow rate improved by 52.3 L/min (95% confidence interval: 27 to 77.5). The forced expiratory volume in one second also improved by 9.8% predicted (95% confidence interval: 3.8 to 15.8). Overall, admission to hospital was not reduced, odds ratio: 0.31 (95% confidence interval: 0.09 to 1.02). In the severe subgroup, admissions were reduced in those receiving magnesium sulfate (odds ratio: 0.10, 95% confidence interval: 0.04 to 0.27). No clinically important changes in vital signs or adverse side effects were reported.
A systematic review including 5 studies with a total of 374 subjects was abstracted in DARE. The overall pooled effect size (ES) for pulmonary function in 4 studies was statistically non significant (ES 0.02, 95% CI: -0.20, +0.24). Pooled results revealed that MgSO4 did not reduce admission rates significantly (OR 0.68, 95% CI: 0.41, 1.15). Side-effects: in one trial minor side-effects such as flushing, mild fatigue, and burning at the intravenous site, were noted in 58% of patients who received MgSO4.