From the Guidelines
Magnesium plays a crucial role in the management of asthma exacerbations by causing relaxation of bronchial smooth muscle independent of serum magnesium level, with IV magnesium sulfate moderately improving pulmonary function in patients with asthma, particularly when combined with nebulized β-adrenergic agents and corticosteroids. According to the 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1, magnesium sulfate can be used to improve pulmonary function in patients with asthma. The mechanisms by which magnesium exerts its effects include:
- Relaxation of bronchial smooth muscle
- Inhibition of the release of histamine and other inflammatory mediators from mast cells
- Reduction of acetylcholine release at neuromuscular junctions, decreasing bronchoconstriction The use of IV magnesium sulfate has been shown to improve pulmonary function and reduce hospital admissions, particularly for patients with severe exacerbations of asthma 1. The standard adult dose of IV magnesium sulfate is 2 g administered over 20 minutes, and it is generally well-tolerated with minor side effects such as flushing and light-headedness 1. In addition to IV magnesium, nebulized magnesium sulfate may also be used as an adjunct to nebulized β-adrenergic agents, although the evidence for its effectiveness is less consistent 1. Overall, magnesium is a valuable adjunctive treatment for asthma exacerbations, particularly in severe or life-threatening cases that have not responded to first-line treatments.
From the Research
Role of Magnesium in Asthma Exacerbation
- Magnesium is a bronchodilator that may provide additional benefit to short-acting inhaled β2-agonists (SABAs) in managing acute asthma exacerbations 2
- Intravenous magnesium sulfate has been shown to reduce hospitalizations and improve pulmonary functions in severe acute asthma exacerbations 2, 3
- Inhaled magnesium sulfate may have benefits with respect to improved pulmonary function and a trend towards benefit in hospital admission, particularly in severe asthma exacerbations 4, 5
Mechanism of Action
- Magnesium takes part in many metabolic processes, including energy metabolism, protein and nucleic acid synthesis, and cell cycle regulation 6
- Magnesium modulates ion transport and influences intracellular calcium concentration, which can affect smooth muscle contractility 6
- Hypomagnesemia may result in an increase in neuromuscular cell excitability, leading to smooth muscle contraction 6
Clinical Use
- Intravenous magnesium sulfate is recommended for use in patients with severe asthma exacerbation not responding to treatment 3, 6
- The British Thoracic Society allows one dose of magnesium sulfate to patients with acute severe asthma exacerbation and inadequate initial response to broncho-dilating inhalation treatment 6
- The efficacy of inhaled magnesium sulfate is still under discussion, and further research is needed to establish its indications and optimal dosage 4, 5