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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral used to treat and prevent hypomagnesemia and for its tocolytic, anticonvulsant, and antiarrhythmic properties.
## Primary Indications
* Hypomagnesemia
* Preeclampsia and eclampsia
* Torsades de Pointes
* Bronchospasm (adjunctive therapy)
* Constipation (oral formulation)
## Adult Dosing
* **Hypomagnesemia (treatment):** Typically 1 to 4 g (8 to 32 mEq) IV infused over 5 to 60 minutes. May be repeated every 4 hours as needed, or as a continuous infusion. Oral doses range from 2.4 to 4.8 g/day divided into doses.
* **Preeclampsia/Eclampsia:** Loading dose: 4 to 6 g IV over 5 to 20 minutes. Maintenance dose: 1 to 2 g/hour IV infusion.
* **Torsades de Pointes:** 1 to 2 g (8 to 16 mEq) IV in 10 mL D5W over 5 to 10 minutes. May repeat after 5 minutes. Further doses may be given as an infusion.
* **Bronchospasm (adjunctive):** 2 g IV infused over 15 to 20 minutes.
## Pediatric Dosing
* **Hypomagnesemia (treatment):** 20 to 50 mg/kg (0.12 to 0.25 mEq/kg) IV infused over 1 to 5 minutes. Maximum dose usually 2 g. May be repeated every 4 to 12 hours. Oral doses are highly variable and depend on age and severity.
* **Eclampsia (adjunctive):** Similar to adults, doses adjusted for weight. Local protocol is critical.
## Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. Use with caution in patients with renal impairment. Reduced doses and/or increased monitoring are necessary. In severe renal impairment, magnesium may accumulate and cause toxicity.
## Contraindications
* Hypermagnesemia
* Heart block greater than first degree (without pacemaker)
* Myocardial infarction
* Hypersensitivity to magnesium sulfate
## Adverse Effects
* **Common:** Flushing, sweating, nausea, vomiting, hypotension, decreased deep tendon reflexes, somnolence.
* **Serious:** Respiratory depression, cardiac arrest, hypermagnesemia (especially in renal impairment), hypocalcemia, hypothermia.
## Key Drug Interactions
* **Neuromuscular blocking agents:** Magnesium can potentiate neuromuscular blockade, potentially leading to prolonged respiratory paralysis.
* **Calcium channel blockers:** Increased risk of hypotension and bradycardia.
* **Bisphosphonates, tetracyclines, fluoroquinolones:** Oral magnesium can decrease the absorption of these agents; administer at least 2 hours apart.
## Monitoring
* Serum magnesium levels (especially with prolonged infusions or renal impairment)
* Deep tendon reflexes
* Respiratory rate and effort
* Blood pressure
* Urine output
* Electrocardiogram (ECG) may be considered in certain situations (e.g., torsades de pointes treatment).
## Clinical Pearls
* IV magnesium sulfate should be administered with caution in patients with myasthenia gravis due to potential neuromuscular blockade potentiation.
* Rapid IV administration can cause hypotension and cardiac arrhythmias. Infuse slowly as recommended.
* Always verify the concentration of magnesium sulfate solutions, as it can vary (e.g., 50% solution is 4.07 mEq/mL).
* Oral magnesium can cause diarrhea; dose adjustment or formulation change may be needed.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.*
