Please check your internet connection and try again.
# Magnesium sulfate
## Overview
Magnesium sulfate is an essential electrolyte used for life-threatening arrhythmias, severe asthma, and obstetric emergencies. It acts as a calcium antagonist and neuromuscular depressant.
## Primary Indications
* **Torsades de pointes (pulseless/with pulse)**
* **Severe acute asthma** (adjunct)
* **Eclampsia/Preeclampsia** (seizure prophylaxis and treatment)
* **Hypomagnesemia** (symptomatic)
## Adult Dosing
* **Torsades de pointes:** 1–2 g IV/IO administered over 5–20 minutes.
* **Severe Acute Asthma:** 2 g IV over 20 minutes as a single dose.
* **Eclampsia/Preeclampsia:** 4–6 g IV bolus over 15–20 minutes, followed by a maintenance infusion of 1–2 g/hour.
* **Hypomagnesemia:** 1–4 g IV (usually 1 g/hr). For severe cases, consider 2-4 g over 15 minutes followed by maintenance.
*Note: Dosing protocols for eclampsia and severe electrolyte repletion vary significantly by local institutional policy.*
## Pediatric Dosing
* **Torsades de pointes:** 25–50 mg/kg IV/IO (max 2 g).
* **Severe Acute Asthma:** 25–75 mg/kg IV (max 2 g) over 20–30 minutes.
* **Hypomagnesemia:** 25–50 mg/kg IV (max 2 g).
## Dose Adjustments
* **Renal Impairment:** Reduce dose and frequency in patients with CrCl < 30 mL/min; accumulation occurs rapidly. Magnesium sulfate is contraindicated in severe renal impairment unless strictly indicated for life-threatening arrhythmias.
## Contraindications
* Heart block (high degree) or myocardial damage.
* Severe renal impairment (CrCl < 30 mL/min).
* Hypocalcemia.
## Adverse Effects
* **Cardiovascular:** Bradycardia, AV block, hypotension (with rapid infusion).
* **Neuromuscular:** Loss of deep tendon reflexes (early sign of toxicity), muscle weakness, respiratory depression.
* **Other:** Flushing, sweating, hypothermia.
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** Potentiates neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of severe hypotension.
* **Digoxin:** May increase risk of cardiac conduction abnormalities.
* **Aminoglycosides:** Potential for increased neuromuscular blockade.
## Monitoring
* **Clinical:** Check patellar reflexes frequently (absent reflexes indicate toxicity). Monitor respiratory rate (keep > 12–16 breaths/min).
* **Serum:** Monitor serum magnesium levels.
* **Toxicity:** If toxicity occurs, stop infusion immediately and administer **Calcium gluconate** (1 g IV) to reverse respiratory/cardiac depression.
## Clinical Pearls
* Rapid IV administration (push) is reserved for life-threatening arrhythmias (Torsades) only. Use infusion pumps for all other indications to avoid precipitous hypotension.
* Always ensure the patient has intact deep tendon reflexes and adequate urine output (> 0.5 mL/kg/hr) before continuing maintenance infusions.
* Magnesium sulfate is not first-line for routine hypomagnesemia if the patient can tolerate oral supplementation (which is better absorbed long-term).
***
**Educational Disclaimer:** This information is for educational purposes only. Always verify dosages, contraindications, and compatibility with your institution's current prescribing protocols and official product labeling (e.g., package insert or Lexicomp) before clinical administration.
