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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral that plays a role in numerous physiological processes, including neuromuscular function, cardiac conduction, and enzyme activity. It is available in intravenous (IV) and intramuscular (IM) formulations.
## Primary Indications
* Treatment of hypomagnesemia.
* Management of severe preeclampsia and eclampsia.
* Management of torsades de pointes.
* Adjunctive treatment for status asthmaticus.
## Adult Dosing
* **Hypomagnesemia:**
* **Mild:** 1-2 grams IV infused over 5-60 minutes, followed by 1 gram IM every 4-12 hours as needed.
* **Severe:** 4-6 grams IV infused over 10-60 minutes, followed by a continuous infusion of 1-2 grams/hour. Dosing depends on local protocol and patient response.
* **Preeclampsia/Eclampsia:** 4-6 grams IV loading dose over 5-20 minutes, followed by a maintenance infusion of 1-2 grams/hour. Dosing depends on local protocol. For eclampsia, an additional 2-4 gram IV bolus may be given if seizures persist.
* **Torsades de Pointes:** 1-2 grams IV diluted in 100 mL D5W infused over 5-10 minutes. Repeat doses may be given every 5-15 minutes.
* **Status Asthmaticus:** 25-40 mg/kg IV (maximum 2 grams) infused over 15-30 minutes.
## Pediatric Dosing
Dosing varies widely based on indication and patient weight. Specific pediatric dosing should be guided by institutional protocols or specialized pediatric references.
* **Hypomagnesemia:** Typically 25-50 mg/kg IV/IM per dose, with maximum doses up to 2 grams.
* **Preeclampsia/Eclampsia:** Not routinely recommended; consult specialists.
* **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 grams) infused over 10-20 minutes.
* **Status Asthmaticus:** 25-40 mg/kg IV (maximum 2 grams) infused over 15-30 minutes.
## Dose Adjustments
* **Renal Impairment:** Reduce dose and monitor serum magnesium levels closely. Elimination is significantly impaired in severe renal insufficiency.
## Contraindications
* Hypermagnesemia.
* Heart block (unless a pacemaker is present).
* Myocardial infarction.
* Profound shock.
* Intended for patients with myasthenia gravis unless directed by a physician.
## Adverse Effects
Common: Flushing, sweating, nausea, vomiting, drowsiness, hypotension.
Serious: Respiratory depression, cardiac arrhythmias, loss of deep tendon reflexes, muscle weakness, hypermagnesemia.
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** May potentiate neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of hypotension and bradycardia.
* **Nifedipine:** Increased risk of hypotension when used concurrently for preeclampsia.
## Monitoring
* **Serum Magnesium Levels:** Monitor regularly, especially with prolonged infusions or impaired renal function. Therapeutic levels are typically 4-7 mg/dL.
* **Renal Function:** Assess baseline and monitor.
* **Vital Signs:** Monitor blood pressure, heart rate, and respiratory rate.
* **Deep Tendon Reflexes:** Assess for depression, which may indicate toxicity.
* **Urine Output:** Monitor for adequate renal function.
## Clinical Pearls
* Rapid IV infusion can cause flushing, sweating, and hypotension. Infuse slowly as recommended.
* Calcium gluconate (1 gram IV) is the antidote for magnesium toxicity.
* Ensure adequate hydration and renal function before administering magnesium sulfate.
* IM injections can be painful; consider lidocaine if administered IM.
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*Disclaimer: This information is intended for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information and institutional protocols before administering any medication.*
