Please check your internet connection and try again.
# Magnesium Sulfate
## Overview
Magnesium sulfate is an electrolyte essential for enzymatic reactions, neuromuscular transmission, and cardiovascular function. It acts as a calcium antagonist and CNS depressant. Administration can be IV (preferred for immediate therapeutic levels) or IM.
## Primary Indications
* **Hypomagnesemia:** Treatment and prevention.
* **Preeclampsia/Eclampsia:** Prophylaxis and treatment of seizures.
* **Torsades de Pointes:** First-line treatment for polymorphic ventricular tachycardia associated with long QT interval.
* **Severe Asthma:** Adjunctive therapy for acute exacerbations unresponsive to initial treatment.
* **Preterm Labor:** Historically used for tocolysis; currently primarily used for fetal neuroprotection.
## Adult Dosing
* **Hypomagnesemia (Mild):** 1–2 g IV/IM every 4–6 hours as needed.
* **Hypomagnesemia (Severe/Symptomatic):** 1–4 g IV over 5–60 minutes; may repeat until levels normalize.
* **Torsades de Pointes:** 1–2 g IV bolus over 5–20 minutes, followed by 0.5–1 g/hour infusion.
* **Eclampsia/Preeclampsia:** 4–6 g IV loading dose over 15–20 minutes, followed by 1–2 g/hour maintenance infusion.
* **Severe Asthma:** 2 g IV over 20 minutes (single dose).
*Note: Always verify doses against local facility protocols (e.g., obstetric vs. emergency usage).*
## Pediatric Dosing
* **Hypomagnesemia:** 25–50 mg/kg/dose IV/IM; may repeat every 4–6 hours for 3–4 doses. Maximum 2 g/dose.
* **Severe Asthma:** 25–50 mg/kg/dose IV over 20 minutes (max 2 g).
## Dose Adjustments
* **Renal Impairment:** Requires dose reduction or longer dosing intervals; significant risk of toxicity due to renal clearance of magnesium. Use with extreme caution (CrCl <30 mL/min).
## Contraindications
* Myocardial damage/Heart block.
* Severe renal impairment (unless specific clinical requirement).
* Hypersensitivity.
* Avoid within 2 hours of delivery if possible to prevent neonatal respiratory/neuromuscular depression.
## Adverse Effects
* **Common:** Flushing, hypotension, bradycardia, muscle weakness.
* **Severe/Toxic:** Loss of deep tendon reflexes (DTRs), respiratory depression (RR <12/min), cardiac arrest/asystole, hypocalcemia.
* **Antidote:** Calcium gluconate 1g IV for severe magnesium toxicity.
## Key Drug Interactions
* **CNS Depressants:** Potentiates effects; use with caution.
* **Neuromuscular Blockers:** Significant potentiation of blockade; increased risk of prolonged paralysis.
* **Digitalis Glycosides:** Use caution; sudden shifts in magnesium can trigger digitalis toxicity.
* **Aminoglycosides:** Potential for additive muscle weakness.
## Monitoring
* **DTRs:** Perform hourly checks; loss of patellar reflex is often the first clinical sign of hypermagnesemia.
* **Respiratory Rate:** Monitor continuously if on high-dose infusions.
* **Urine Output:** Ensure >30 mL/hour to prevent toxicity (renal clearance maintenance).
* **Serum Magnesium:** Monitor levels (Goal: 4–7 mEq/L for eclampsia; 1.8–2.4 mg/dL for maintenance).
* **Serum Calcium:** Monitor for potential hypocalcemia.
## Clinical Pearls
* Rapid IV administration can cause extreme hypotension and cardiac collapse; infusion rates should be strictly controlled.
* In obstetric settings, magnesium toxicity is monitored via the presence of the patellar reflex, respiratory rate, and urine output.
* Magnesium sulfate is not dialyzable; patients with severe renal failure require strict monitoring for accumulation.
***
**Educational Disclaimer:** This information is for educational purposes only and does not reflect official medical advice. Always refer to your institution’s current prescribing information, Clinical Decision Support systems, or the package insert before dosing. Verify all patient-specific factors, including renal function and concomitant medications, before administration.
