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## Magnesium Sulfate
### Overview
Magnesium sulfate is an essential mineral that plays a vital role in numerous biochemical functions. It is available for intravenous (IV) and intramuscular (IM) administration.
### Primary Indications
* Treatment of hypomagnesemia
* Management of severe preeclampsia and eclampsia
* Management of status epilepticus refractory to standard therapy
* Treatment of torsades de pointes
### Adult Dosing
* **Hypomagnesemia:**
* **Mild:** 1 gram IV infused over 5-60 minutes, followed by 1 gram IM every 4-6 hours for 3-4 doses.
* **Severe (symptomatic or serum Mg < 1 mg/dL):** 4-5 grams IV infused over 10-15 minutes, followed by a continuous infusion of 1-2 grams/hour.
* **Preeclampsia/Eclampsia:** Loading dose: 4-6 grams IV over 5-20 minutes. Maintenance infusion: 1-2 grams/hour. For eclampsia, an additional 2-4 grams IV may be given slowly.
* **Status Epilepticus (refractory):** 1-2 grams IV infused over 5-10 minutes.
* **Torsades de Pointes:** 1-2 grams IV infused over 5-10 minutes. May be followed by infusion of 0.5-1 gram/hour if needed.
### Pediatric Dosing
Dosing in pediatric patients is highly variable and often based on protocol.
* **Hypomagnesemia:** 20-50 mg/kg/dose IV or IM, up to a maximum of 2 grams per dose. May be repeated every 4-12 hours.
* **Eclampsia:** 40 mg/kg IV, maximum 2 grams. Followed by infusion of 10-20 mg/kg/hour.
### Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. Use with caution in patients with renal impairment. Reduce dose and monitor magnesium levels closely.
### Contraindications
* Hypermagnesemia
* Heart block greater than first degree
* Myocardial infarction (relative contraindication)
* Pulmonary edema
* Hypotension
* Myasthenia gravis (caution)
### Adverse Effects
* **Common:** Flushing, sweating, hypotension, nausea, vomiting, hypothermia, drowsiness.
* **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, loss of deep tendon reflexes, hypermagnesemia (especially in renal impairment).
### Key Drug Interactions
* **Neuromuscular Blockers:** Potentiates neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of hypotension and bradycardia.
* **Antihypertensives:** Additive hypotensive effects.
* **Tetracyclines and Fluoroquinolones:** Magnesium can decrease absorption; separate administration by at least 2 hours.
### Monitoring
* Serum magnesium levels (especially with continuous infusions or renal impairment)
* Blood pressure
* Respiratory rate
* Deep tendon reflexes
* Urine output
* Electrocardiogram (ECG) in critical care settings
### Clinical Pearls
* Magnesium sulfate is a CNS depressant and a vasodilator.
* Rapid IV administration can cause flushing, hypotension, and cardiac arrhythmias.
* Monitor for signs of hypermagnesemia, particularly in patients with impaired renal function.
* In hypomagnesemia, concomitant electrolyte abnormalities (e.g., hypokalemia, hypocalcemia) should be assessed and treated.
* For IM administration, divide doses between two sites to minimize pain and induration.
**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and local protocols for definitive guidance.
