Intravenous magnesium sulphate provides no additive benefit to standard management in acute asthma

Summary Background Treatment of acute asthma is based on rapid reversal of bronchospasm and airway inflammation. Magnesium sulphate (MgSO 4 ) is known to have a bronchodilator effect on smooth muscle but studies have shown conflicting results on its efficacy in acute asthma, although its use is recommended in national and international guidelines. Aims To determine if intravenous MgSO 4 , when used as an adjunct to standard therapy, improves the outcome in acute asthma. Methods A double blind, randomised placebo controlled trial comparing 1.2g MgSO 4 with standard therapy in adult patients with acute asthma. Patients had a PEF ⩽75% predicted and all were treated with oxygen, nebulised salbutamol and ipratropium, and IV hydrocortisone. They then received 1.2g IV MgSO 4 or placebo. Outcome measures were % predicted PEF at 60min and hospital admission rates. Results One hundred and twenty nine patients were studied. Placebo and active treatment groups were well matched at baseline. MgSO 4 had no benefit with regards hospital admission rates or % predicted PEF at 60min ( p =0.48) for the whole group, or for subgroups of life-threatening ( p =0.85), severe ( p =0.63) and moderate ( p =0.67) acute asthma. Conclusion This study did not show additional benefit from 1.2g IV MgSO 4 when given as an adjunct to standard therapy for acute asthma.