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

SummaryBackgroundTreatment of acute asthma is based on rapid reversal of bronchospasm and airway inflammation. Magnesium sulphate (MgSO4) 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.AimsTo determine if intravenous MgSO4, when used as an adjunct to standard therapy, improves the outcome in acute asthma.MethodsA double blind, randomised placebo controlled trial comparing 1.2 g MgSO4 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 1.2 g IV MgSO4 or placebo. Outcome measures were % predicted PEF at 60 min and hospital admission rates.ResultsOne hundred and twenty nine patients were studied. Placebo and active treatment groups were well matched at baseline. MgSO4 had no benefit with regards hospital admission rates or % predicted PEF at 60 min (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.ConclusionThis study did not show additional benefit from 1.2 g IV MgSO4 when given as an adjunct to standard therapy for acute asthma.