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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral that plays a role in numerous biochemical processes, including neuromuscular transmission and muscle contraction. It is available for intravenous (IV), intramuscular (IM), and oral administration.
## Primary Indications
* **Hypomagnesemia:** Treatment of low magnesium levels.
* **Preeclampsia/Eclampsia:** Prevention and treatment of seizures in patients with preeclampsia and eclampsia.
* **Torsades de Pointes:** Treatment of polymorphic ventricular tachycardia.
* **Bronchodilator:** Adjunctive therapy for severe bronchospasm in asthma or COPD exacerbations.
* **Constipation (Oral):** Osmotic laxative.
## Adult Dosing
* **Hypomagnesemia:**
* **Acute severe deficiency:** 4-6 grams IV initially, followed by 2-4 grams every 4-6 hours as needed. Dosing adjusted based on serum magnesium levels.
* **Less severe deficiency:** 1-2 grams IV or IM every 6-12 hours.
* **Maintenance:** 4-6 grams per day divided into 4 doses IM or IV.
* **Preeclampsia/Eclampsia:**
* **Loading Dose:** 4-6 grams IV infused over 5-20 minutes.
* **Maintenance Dose:** 1-2 grams per hour IV infusion. Dosing may vary based on local protocol and patient response.
* **Torsades de Pointes:** 1-2 grams IV diluted in 10-20 mL of D5W, infused over 5-10 minutes. May repeat if necessary. Subsequent infusion of 0.5-1 gram per hour.
* **Bronchodilator:** 1-2 grams IV infused over 15-30 minutes.
* **Constipation (Oral):** 15-30 mL of a 50% solution once daily or as needed.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing is highly variable and based on serum magnesium levels and weight. Consult specialized pediatric resources or local protocols.
* **Example (Neonates):** 25-50 mg/kg/dose IV every 12-24 hours.
* **Example (Children):** 25-50 mg/kg/dose IV or IM, not to exceed 2 grams per dose.
* **Eclampsia:** Dosing often follows adult guidelines, but specific protocols may exist.
* **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 grams).
## Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. Use with caution and reduced doses in patients with impaired renal function. Monitor serum magnesium levels closely.
## Contraindications
* Hypermagnesemia
* Heart block
* Myocardial infarction (in some cases of Torsades de Pointes)
* Hyperparathyroidism
* Addison's disease
* Gastrointestinal obstruction (for oral administration)
## Adverse Effects
* **Cardiovascular:** Hypotension, bradycardia, ECG changes, cardiac arrest.
* **Neuromuscular:** Flushing, sweating, drowsiness, hyporeflexia, muscle weakness, respiratory depression, coma.
* **Gastrointestinal (Oral):** Diarrhea, abdominal cramping.
* **Other:** Hyperthermia.
## Key Drug Interactions
* **Neuromuscular Blockers:** May potentiate neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of hypotension and neuromuscular blockade.
* **Antibiotics (Aminoglycosides, Tetracyclines):** May impair aminoglycoside activity; may decrease tetracycline absorption.
* **Bisphosphonates:** May decrease absorption.
* **Digitalis:** May increase risk of digitalis toxicity.
## Monitoring
* **Serum Magnesium Levels:** Crucial for guiding dosing, especially in hypomagnesemia and renal impairment.
* **Renal Function:** Monitor BUN, creatinine, and urine output.
* **Vital Signs:** Blood pressure, heart rate, respiratory rate.
* **Deep Tendon Reflexes:** Assess for loss of reflexes, indicative of hypermagnesemia.
* **ECG:** Monitor for changes, especially in patients receiving IV magnesium for cardiac arrhythmias.
## Clinical Pearls
* Magnesium sulfate administration, especially IV, can cause flushing, warmth, and sedation.
* Rapid IV infusion can lead to hypotension and cardiovascular collapse. Infuse slowly as recommended.
* In cases of hypomagnesemia, concurrent hypokalemia and hypocalcemia are common and may require correction.
* For oral administration, magnesium citrate can cause diarrhea.
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*This information is intended for healthcare professionals and does not replace official prescribing information. Always consult the most current drug product labeling and institutional protocols before prescribing or administering any medication.*
