What is the recommended dose of magnesium sulfate (MgSO4) for pediatric patients with asthma exacerbation?

Magnesium Sulfate Dosing for Pediatric Asthma Exacerbation

For pediatric patients with severe asthma exacerbations not responding to conventional therapy, the recommended dose of intravenous magnesium sulfate is 50 mg/kg (maximum 2 grams) administered over 20 minutes. 1

Indications for Magnesium Sulfate Use

Magnesium sulfate should be used selectively in pediatric asthma exacerbations:

• Not recommended for mild exacerbations
• Consider for:
  • Life-threatening exacerbations
  • Severe exacerbations that remain severe after 1 hour of intensive conventional therapy 1
  • Patients with FEV1 between 40-75% predicted 2

Administration Protocol

1. Dosage: 50 mg/kg (maximum 2 grams) 1
2. Administration rate: Infuse over 20 minutes 1
3. Monitoring: Observe for hypotension, flushing, and muscle weakness during administration

Mechanism and Benefits

Magnesium sulfate causes relaxation of bronchial smooth muscle independent of serum magnesium level. When combined with nebulized β-adrenergic agents and corticosteroids, IV magnesium sulfate can:

• Moderately improve pulmonary function
• Reduce hospital admissions
• Improve FEV1, FEV1/FVC ratio, PEF, and FEF25-75 parameters 2

Alternative Dosing Regimens

Some centers use continuous infusion protocols for refractory cases:

• 50 mg/kg/hour over 4 hours 3
• 40-50 mg/kg/hour for 4-5 hours 4

However, these extended infusion protocols should be reserved for refractory cases only, as they lack robust evidence and may increase risk of adverse effects 4.

Caution

Doses exceeding 27 mg/kg in children <40 kg have been associated with increased need for escalation in therapy, including mechanical ventilation or additional rescue medications 5. Common side effects include:

• Hypotension (16.6%)
• Nausea/vomiting (7.8%)
• Mild muscle weakness (4.9%)
• Flushing (2.2%)
• Sedation (0.4%) 4

Treatment Algorithm

1. First-line therapy:

   • Oxygen supplementation
   • Inhaled short-acting β2-agonists (e.g., albuterol)
   • Systemic corticosteroids

2. If inadequate response after 1 hour:

   • Add IV magnesium sulfate 50 mg/kg (max 2 grams) over 20 minutes

3. If still inadequate response:

   • Consider ICU transfer
   • Consider additional therapies (heliox, mechanical ventilation)

Magnesium sulfate should be considered an important adjunctive therapy for severe asthma exacerbations in children, with demonstrated improvements in pulmonary function and clinical outcomes when used appropriately 6, 2.