Magnesium Sulfate Dosing for Pediatric Asthma Exacerbations
For pediatric patients with severe acute asthma exacerbations not responding to conventional therapy, intravenous magnesium sulfate should be administered at 50 mg/kg (maximum 2 g) over 20 minutes. 1
Indications for Use
Magnesium sulfate is indicated as an adjunctive therapy when:
- Patient has a severe asthma exacerbation
- Patient has not responded adequately to initial treatment with:
- Inhaled β2-agonists
- Systemic corticosteroids
- Ipratropium bromide
Dosing Guidelines
Intravenous Administration
- Standard dose: 50 mg/kg administered over 20 minutes (maximum 2 g) 1
- Administration rate: Infuse over 20 minutes to minimize side effects 1
- Maximum dose: 2 grams (adult equivalent dose) 1
Important Considerations
- Dosing above 27 mg/kg has been associated with increased need for escalation of therapy in children <40 kg, suggesting that higher doses may indicate more severe disease rather than providing additional benefit 2
- Recent pharmacokinetic data suggests that doses between 50-75 mg/kg may be required to achieve therapeutic serum concentrations (25-40 mg/L) 3
- The most recent pharmacodynamic research (2025) suggests targeting a total serum magnesium AUC0-2h >63.1 mg·h/L for optimal efficacy 4
Continuous Infusion Option
For patients with severe refractory asthma, an alternative approach:
- Initial bolus followed by continuous infusion at 50 mg/kg/h for 4 hours 5
- This approach has shown good tolerability and improved respiratory status in refractory cases
Monitoring During Administration
- Vital signs (particularly blood pressure)
- Oxygen saturation (maintain SpO2 >92%)
- Clinical asthma score
- Side effects: flushing, light-headedness, hypotension
Efficacy and Safety Profile
- Magnesium causes bronchial smooth muscle relaxation independent of serum magnesium level 1
- Minor side effects include flushing and light-headedness 1
- Hypotension is uncommon in properly dosed pediatric patients 4
- Provides improved pulmonary function and reduced hospital admissions, particularly in severe exacerbations 1, 6
Clinical Pearls
- Magnesium sulfate should be considered early in treatment for severe exacerbations
- Most effective when combined with nebulized β-adrenergic agents and corticosteroids
- Particularly beneficial for patients with the most severe exacerbations
- Has a short serum half-life (approximately 2.7 hours) in children 3
- Should be administered in a monitored setting with capability for blood pressure monitoring
The evidence strongly supports using magnesium sulfate as an effective adjunctive therapy for severe pediatric asthma exacerbations, with a well-established safety profile when properly dosed and administered.