Purpose of review: Acute asthma is common and severe exacerbations may result in hospitalization, need for endotracheal intubation and, rarely, death. Standard emergency care includes systemic corticosteroids and bronchodilators, but additional treatments may be required in severe cases. We summarize the substantial evidence regarding the role of MgSO4 in acute asthma and comments on the potential benefit in chronic asthma.
Recent findings: Inhaled and intravenous MgSO4 agents are used in the treatment of acute asthma, but only the intravenous formulation is effective. In severe asthma exacerbations, a single bolus dose of intravenous MgSO4 reduces admissions and improves pulmonary functions. Inhaled MgSO4 is more effective than placebo as a bronchodilator, but performs no better than salbutamol and there is no apparent synergy when the two are combined. Whereas intravenous MgSO4 treatments appear to be effective, long-term 'replacement' therapy with magnesium does not appear to affect chronic asthma.
Summary: Evidence suggests that intravenous MgSO4 is beneficial in acute asthma, while the evidence for inhaled MgSO4 is less convincing. Moreover, the role of replacement therapy with oral magnesium remains to be clarified. The use of intravenous MgSO4 remains uncommon, with emergency physicians appropriately restricting its use to patients with severe exacerbations.