Please check your internet connection and try again.
# Magnesium sulfate
## Overview
Magnesium sulfate is an essential electrolyte used for the treatment of hypomagnesemia, eclampsia, and refractory arrhythmias. It primarily acts as a calcium antagonist and CNS depressant. Route and concentration (e.g., 50% vs. 10% solution) vary significantly by indication.
## Primary Indications
* Hypomagnesemia (symptomatic or severe).
* Eclampsia and pre-eclampsia (seizure prophylaxis).
* Torsades de pointes (ACLS protocol).
* Adjunctive therapy for severe asthma exacerbations (unresponsive to standard therapy).
## Adult Dosing
* **Hypomagnesemia:** 1–4 g IV/IM. Common regimen: 1–2 g IV over 15–60 minutes. Severe deficiency can require 4–8 g over 12–24 hours.
* **Eclampsia/Pre-eclampsia:** 4–6 g IV loading dose over 15–20 minutes, followed by 1–2 g/hour IV infusion. Continue for 24 hours post-delivery.
* **Torsades de Pointes/Cardiac Arrest:** 1–2 g IV push (over 5–20 minutes).
* **Severe Asthma:** 2 g IV over 20 minutes (single dose).
## Pediatric Dosing
* **Hypomagnesemia:** 25–50 mg/kg/dose IV/IM (max 2 g/dose) q4–6h for 3–4 doses.
* **Status Asthmaticus (Off-label):** 25–50 mg/kg (max 2 g) IV infusion over 20 minutes.
* *Note: Always verify pediatric dosing against weight-based institutional protocols/charts.*
## Dose Adjustments
* **Renal Impairment:** Reduce dose and frequency in patients with CrCl <30 mL/min; magnesium is exclusively renally excreted. Monitor serum levels closely to avoid toxicity.
## Contraindications
* Heart block (unless pacemaker present).
* Myocardial damage.
* Severe renal impairment (CrCl <20 mL/min).
* Persistent oliguria.
## Adverse Effects
* **Common:** Flushing, diaphoresis, hypotension, warmth.
* **Serious:** Magnesium toxicity (loss of deep tendon reflexes, respiratory depression, bradycardia, cardiac arrest).
* **Treatment of Toxicity:** Stop infusion immediately. Administer **Calcium gluconate** (1 g IV) as an antidote to reverse respiratory/cardiac depression.
## Key Drug Interactions
* **CNS Depressants:** May potentiate sedation.
* **Neuromuscular Blockers:** Significant potentiation; monitor for prolonged paralysis.
* **Aminoglycosides:** Potential for increased neuromuscular blockade.
* **Digitalis Glycosides:** Use caution; rapid magnesium infusion may cause arrhythmias in digitalized patients.
## Monitoring
* **Serum Magnesium:** Maintain therapeutic range (typically 1.7–2.2 mg/dL for maintenance; 4–7 mEq/L or 4.8–8.4 mg/dL for eclampsia).
* **Clinical:** Deep tendon reflexes (DTRs), respiratory rate (must be >12/min), urine output (must be >0.5 mL/kg/hr or >30 mL/hr).
## Clinical Pearls
* **Administration:** Always confirm concentration. Using 50% solution undiluted for IV bolus is dangerous; dilute to 10% or 20% concentration for most IV peripheral administration to reduce vein irritation.
* **Asthma:** Magnesium acts as a smooth muscle relaxant; it does not replace bronchodilators but serves as an adjunct.
* **Protocol Dependency:** Always follow institutional "Magnesium Sulfate Order Sets," particularly in OB/GYN settings where infusion rates differ based on local safety guidelines.
***
**Disclaimer:** This information is for educational purposes only. Always verify drug doses, contraindications, and compatibility with current prescribing information, institutional protocols, and official pharmaceutical databases (e.g., Lexicomp, Micromedex) before administration.
