What is the recommended intravenous (IV) dose and rate of magnesium for acute asthma exacerbation?

From the Guidelines

For acute severe asthma exacerbations, intravenous magnesium sulfate should be administered at a dose of 2 grams (or 25-75 mg/kg in children) diluted in 50-100 mL of normal saline and infused over 20 minutes, as this has been shown to moderately improve pulmonary function and reduce hospital admissions 1.

Key Considerations

• The dose of 2 grams over 20 minutes in adults and 25 to 75 mg/kg in children (up to a maximum of 2 g) is recommended 2.
• Magnesium works as a bronchodilator by relaxing smooth muscle and may reduce inflammation in the airways.
• It's typically used as an adjunct therapy when patients have not responded adequately to standard treatments like inhaled beta-agonists, anticholinergics, and systemic corticosteroids.
• Potential side effects include flushing, hypotension, respiratory depression, and loss of deep tendon reflexes, and magnesium levels should be checked if repeated doses are considered.
• The medication should be used cautiously in patients with renal impairment.

Administration and Monitoring

• The infusion should not be given as a rapid bolus due to the risk of hypotension.
• Patients should be monitored during administration for potential side effects.
• This intervention is most effective when given early in the course of treatment for severe exacerbations.

Evidence Summary

• A Cochrane meta-analysis of 7 studies concluded that IV magnesium sulfate improves pulmonary function and reduces hospital admissions, particularly for patients with the most severe exacerbations of asthma 1.
• The use of nebulized magnesium sulfate as an adjunct to nebulized β-adrenergic agents has been reported to improve FEV1 and SpO2, although a prior meta-analysis demonstrated only a trend toward improved pulmonary function with nebulized magnesium 1.

From the FDA Drug Label

DOSAGE & ADMINISTRATION Dosage of magnesium sulfate must be carefully adjusted according to individual requirements and response, and administration of the drug should be discontinued as soon as the desired effect is obtained. The rate of IV injection should generally not exceed 150 mg/minute (1. 5 mL of a 10% concentration or its equivalent)

The recommended intravenous (IV) dose and rate of magnesium for acute asthma exacerbation is not explicitly stated in the provided drug label. However, the label does provide a general guideline for the rate of IV injection, which should not exceed 150 mg/minute.

• The maximum dose for other conditions is mentioned, but not specifically for acute asthma exacerbation.
• Key considerations for dosage adjustment include individual requirements and response, as well as discontinuation of administration once the desired effect is obtained 3.

From the Research

Recommended IV Dose and Rate of Magnesium for Acute Asthma Exacerbation

• The recommended intravenous (IV) dose of magnesium sulfate for acute asthma exacerbation is typically a single bolus dose, with studies suggesting doses of 1.2 g or 2 g 4.
• The IV rate of administration is usually over 15 to 30 minutes 4.
• The use of IV magnesium sulfate is generally recommended for patients with severe acute asthma exacerbations who have not responded sufficiently to standard treatments such as oxygen, nebulised short-acting beta2-agonists, and IV corticosteroids 5, 6, 4.

Evidence for IV Magnesium Sulfate in Acute Asthma

• Studies have shown that IV magnesium sulfate can reduce hospital admissions and improve lung function in adults with acute asthma 4.
• A systematic review of 14 studies found that IV magnesium sulfate reduced hospital admissions compared with placebo, with an odds ratio of 0.75 (95% CI 0.60 to 0.92) 4.
• Another study found that IV magnesium sulfate improved peak expiratory flow rates and forced expiratory volume in one second in patients with severe acute asthma 7.

Safety and Adverse Events

• IV magnesium sulfate is generally considered safe, with common adverse events including flushing, fatigue, nausea, headache, and hypotension (low blood pressure) 4.
• However, adverse events were not consistently reported across studies, and further research is needed to fully assess the safety of IV magnesium sulfate in acute asthma 4.