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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential electrolyte acting as a physiological calcium channel blocker and cofactor in enzymatic reactions. It is primarily used for its neuromuscular and cardiovascular stabilization properties.
## Primary Indications
* **Hypomagnesemia:** Treatment and prophylaxis of magnesium deficiency.
* **Obstetrics:** Eclampsia and pre-eclampsia (seizure prophylaxis/treatment).
* **Cardiology:** Torsades de pointes (refractory ventricular tachycardia).
* **Pulmonology:** Severe, refractory acute asthma exacerbations (adjunctive therapy).
## Adult Dosing
* **Hypomagnesemia:** 1–4 g IV/IM. Common protocol: 2–4 g over 1–4 hours.
* **Torsades de Pointes:** 1–2 g IV push over 5–20 minutes, may repeat once.
* **Eclampsia:** Loading dose of 4–6 g IV over 15–30 minutes, followed by 1–2 g/hour maintenance infusion.
* **Severe Asthma:** 2 g IV bolus over 20 minutes as a one-time dose.
* *Note: Dosing varies significantly by institutional protocol; verify local guidelines.*
## Pediatric Dosing
* **Hypomagnesemia:** 25–50 mg/kg/dose IV/IM (max 2 g/dose), may repeat q6h as needed.
* **Asthma:** 25–75 mg/kg IV (max 2 g) administered over 20–30 minutes.
* *Note: Pediatric dosing requires weight-based calculation and strict adherence to flow rate limits.*
## Dose Adjustments
* **Renal Impairment:** Requires significant caution. Reduce dose by 50% or more in patients with renal failure (CrCl < 30 mL/min); avoid if possible due to risk of accumulation and toxicity.
## Contraindications
* Myocardial damage (heart block).
* Severe renal impairment (unless managed under strict monitoring).
* Hypersensitivity to the product.
* Avoid administration 2 hours prior to delivery if possible (to prevent neonatal hypermagnesemia).
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, transient hypotension, nausea.
* **Severe (Toxicity):** Loss of deep tendon reflexes (early sign), respiratory depression, cardiac arrest, bradycardia, complete heart block.
## Key Drug Interactions
* **Neuromuscular Blockers:** Potentiates effects (increased risk of paralysis).
* **CNS Depressants:** Enhances sedative effects.
* **Digitalis Glycosides:** Use caution; rapid administration may cause cardiac conduction changes (arrhythmias).
* **Aminoglycosides:** May potentiate neuromuscular blockade.
## Monitoring
* **Magnesium Levels:** Target 1.5–2.5 mg/dL (therapeutic range varies by indication).
* **Clinical:** Monitor respiratory rate (must be >16 bpm), blood pressure, and deep tendon reflexes (patellar reflex) hourly during parenteral infusions.
* **Renal:** Urinary output (>30 mL/hour or 0.5 mL/kg/hr) is required prior and during infusion.
* **Reversal Agent:** Calcium gluconate 1g IV should be immediately available to treat toxicity.
## Clinical Pearls
* Rapid IV administration can cause extreme hypotension and cardiac collapse.
* Always distinguish between magnesium sulfate and magnesium oxide/citrate (formulations are not interchangeable).
* In asthma, evidence supports use only in patients who fail to respond to standard inhaled beta-agonists and corticosteroids within the first hour.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice is subject to institutional protocols and regional variations. Always verify current prescribing information, package inserts, and hospital guidelines before administering medication.
