Use of isotonic nebulised magnesium sulphate as an adjuvant to salbutamol in treatment of severe asthma in adults: randomised placebo-controlled trial

Background Intravenous magnesium can cause bronchodilation in treatment of severe asthma, however its effect by the nebulised route is uncertain. We aimed to assess the effectiveness of isotonic magnesium sulphate as an adjuvant to nebulised salbutamol in severe attacks of asthma. Methods We enrolled 52 patients with severe exacerbations of asthma presenting to the emergency departments at two hospitals in New Zealand. A severe exacerbation was defined as a forced expiratory volume at 1 s (FEV1) of less than 50% predicted 30 min after initial administration of 2.5 mg salbutamol via nebulisation. In this randomised double-blind placebo-controlled trial patients received 2.5 mg nebulised salbutamol mixed with either 2.5 mL isotonic magnesium sulphate or isotonic saline on three occasions at 30 min intervals. The primary outcome measure was FEV1 at 90 min. Analysis was per protocol. Findings At 90 min the mean FEV1 in the magnesium group was 1.96 L (95% CI 1.68-2.24) and in the saline group 1.55 L (1.24-1.87). The difference in the mean FEV1 between the magnesium and saline groups was 0.37 L (0.13-0.61, p=0.003). Interpretation Use of isotonic magnesium as an adjuvant to nebulised salbutamol results in an enhanced bronchodilator response in treatment of severe asthma.