Magnesium Sulfate Dosing for Pediatric Patients
For pediatric patients requiring magnesium sulfate, the recommended dose depends on the indication, with 25-50 mg/kg (maximum 2 grams) for severe asthma exacerbations and torsades de pointes being the most evidence-based dosing regimen.
Dosing by Indication
Severe Asthma Exacerbations
- Initial IV bolus: 25-50 mg/kg (maximum dose: 2 grams) 1
- Administration rate: Give over 20 minutes for asthma exacerbations 1
- Continuous infusion option: For refractory cases, 40-50 mg/kg/hour for 4 hours may be considered 2, 3
Torsades de Pointes
- IV dose: 25-50 mg/kg (maximum dose: 2 grams) 1
- Administration: Rapid IV infusion over several minutes for torsades de pointes 1
Parenteral Nutrition
- For neonates and children requiring magnesium supplementation in parenteral nutrition:
- Preterm neonates: 0.1-0.4 mmol/kg/day
- Term neonates: 0.1-0.2 mmol/kg/day
- Children: 0.1-0.2 mmol/kg/day 1
Clinical Considerations
Monitoring
- Vital signs: Monitor blood pressure, heart rate, and respiratory rate during administration
- Serum levels: Check magnesium levels after administration in prolonged therapy
- Target serum level: 4-6 mg/dL for therapeutic effect 4
- Clinical response: Assess respiratory status (work of breathing, oxygen saturation) in asthma cases
Precautions
- Renal impairment: Reduce dose in patients with renal dysfunction
- Maternal exposure: Limit magnesium in newborns whose mothers received magnesium sulfate before delivery 1
- Hypotension risk: Diastolic hypotension is common (48% of cases) but rarely requires intervention 4
- Administration route: Use magnesium sulfate rather than magnesium chloride to avoid metabolic acidosis 1
Efficacy Evidence
- In severe asthma, magnesium sulfate improves pulmonary function and reduces hospital admissions 1
- Higher doses (40 mg/kg) have shown significant improvement in pulmonary function tests in children with moderate to severe asthma 5
- Continuous infusions (50 mg/kg/hr for 4 hours) have been well-tolerated with few side effects 3, 4
Potential Adverse Effects
- Hypotension (primarily diastolic)
- Flushing
- Nausea/vomiting (22.7% of cases)
- Transient weakness (14.9% of cases) 4
- Discomfort at infusion site
Important Caveats
- Magnesium sulfate should not be used routinely for mild asthma exacerbations 1
- Consider magnesium sulfate only after failure of conventional therapy (bronchodilators and corticosteroids) 6
- Prolonged infusions appear safe but require monitoring of serum magnesium levels 4
- Calcium chloride should be available to reverse potential magnesium toxicity 1
Remember that magnesium sulfate is typically considered a second-line or adjunctive therapy for severe cases not responding to first-line treatments, particularly in asthma management.