From the Guidelines
Magnesium sulfate dosing for respiratory distress in adults is typically 2 grams administered intravenously over 20 minutes, while for pediatric patients, it is weight-based at 25-50 mg/kg per dose (maximum 2 grams) administered over 20 minutes. This recommendation is based on the most recent and highest quality evidence available, including a study published in the journal Circulation in 2010 1, which suggests that IV magnesium sulfate can moderately improve pulmonary function in patients with asthma when combined with nebulized β-adrenergic agents and corticosteroids.
For pediatric patients, the dosing guidelines are further supported by a study published in the journal Pediatrics in 2008 1, which recommends a weight-based dose of 25-50 mg/kg (maximum 2 g) administered over 10-20 minutes for hypomagnesemia or torsades de pointes, and over 15-30 minutes for status asthmaticus.
Key considerations when administering magnesium sulfate include:
- Monitoring patients for signs of toxicity, such as hypotension, respiratory depression, loss of deep tendon reflexes, and cardiac arrhythmias
- Assessing renal function before administration, as the medication is excreted by the kidneys, and dose adjustments may be necessary in patients with renal impairment
- Monitoring magnesium levels during prolonged therapy, aiming for serum concentrations of 4-6 mg/dL for optimal therapeutic effect without toxicity
- Having calcium chloride available to reverse magnesium toxicity if needed, particularly in cases of rapid infusion which may cause hypotension and bradycardia 1.
Overall, magnesium sulfate is a valuable adjunctive treatment for respiratory distress, particularly in cases of severe bronchospasm unresponsive to first-line treatments, and its use should be guided by careful consideration of the patient's age, weight, and renal function, as well as close monitoring for potential toxicity.
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. In the treatment of mild magnesium deficiency, the usual adult dose is 1 g, equivalent to 8. 12 mEq of magnesium (2 mL of the 50% solution) injected IM every six hours for four doses (equivalent to a total of 32.5 mEq of magnesium per 24 hours). For severe hypomagnesemia, as much as 250 mg (approximately 2 mEq) per kg of body weight (0. 5 mL of the 50% solution) may be given IM within a period of four hours if necessary. In Hyperalimentation In TPN, maintenance requirements for magnesium are not precisely known The maintenance dose used in adults ranges from 8 to 24 mEq (1 to 3 g) daily; for infants, the range is 2 to 10 mEq (0.25 to 1.25 g) daily.
The dosing statistics for magnesium sulfate in pediatric and adult patients with respiratory distress or failure are not explicitly stated in the provided drug label. However, the label provides general dosing guidelines for magnesium sulfate in various conditions, including:
- Adults: 1 g (8.12 mEq) every 6 hours for mild magnesium deficiency, and up to 250 mg (2 mEq) per kg of body weight for severe hypomagnesemia.
- Infants: 2 to 10 mEq (0.25 to 1.25 g) daily for maintenance requirements in TPN. It is essential to note that the label does not provide specific dosing recommendations for respiratory distress or failure, and the dosage should be carefully adjusted according to individual requirements and response 2.
From the Research
Magnesium Sulfate in Pediatric Patients
- The study 3 found that intravenous magnesium sulfate significantly reduced the percentage of children who required mechanical ventilation support in acute severe asthma exacerbations.
- A dose of 50 mg/kg/h in 4 h of continuous infusion of magnesium sulfate was well tolerated and led to improved respiratory status in children with severe acute asthma 4.
- Early administration of intravenous magnesium sulfate (0.2 ml/kg of 50% MgSO4) showed early and significant improvement in PEFR and SaO2 in children with acute severe asthma not responding to conventional therapy 5.
Magnesium Sulfate in Adult Patients
- Inhaled magnesium sulfate (333 mg) added to standard therapy improved FEV(1)%p and SpO(2) post-BD and reduced the rate of ED admissions in adults with severe asthma crisis 6.
- A case study 7 reported the use of IV magnesium sulfate (1 g) to prevent intubation and assisted ventilation in a 72-year-old man with acute respiratory failure complicating asthma.