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# Magnesium Sulphate
## Overview
Magnesium sulfate is an essential mineral involved in numerous enzymatic reactions. It is administered intravenously (IV) or intramuscularly (IM) for various indications.
## Primary Indications
* Treatment of hypomagnesemia.
* Prevention and treatment of eclampsia and preeclampsia.
* Management of torsades de pointes.
* Management of status asthmaticus (adjunctive therapy).
* Treatment of severe alcohol withdrawal.
## Adult Dosing
* **Hypomagnesemia:**
* Severe deficiency: 4-5 g IV infused over 5-60 minutes, followed by 1-2 g/hour via continuous infusion, adjusted based on serum magnesium levels.
* Less severe deficiency: 1-2 g IV or IM every 4-6 hours for 3-4 doses.
* **Eclampsia/Preeclampsia (treatment):** 4-6 g IV bolus over 5-10 minutes, followed by a continuous infusion of 1-2 g/hour. Alternatively, 4-5 g IM in each buttock every 4 hours.
* **Torsades de Pointes:** 1-2 g IV in 10 mL D5W over 5-10 minutes. May repeat.
* **Status Asthmaticus:** 2 g IV over 20 minutes.
* **Alcohol Withdrawal:** 2-4 g IV or IM.
## Pediatric Dosing
* **Hypomagnesemia:** 20-50 mg/kg/dose (elemental magnesium) IV infused over 5-10 minutes. Maximum dose typically 2 g. For severe deficiency, may require continuous infusion. Specific protocols vary.
* **Eclampsia/Preeclampsia:** Refer to obstetric protocols; generally similar to adult dosing adapted for weight.
* **Torsades de Pointes:** 25-50 mg/kg IV infused over 10-20 minutes (maximum 2 g).
* **Status Asthmaticus:** 25-40 mg/kg IV infused over 20 minutes (maximum 2 g).
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduce dose and monitor serum magnesium and renal function closely. Severe impairment may necessitate discontinuing the drug.
## Contraindications
* Myocardial damage.
* Heart block.
* Hypermagnesemia.
* Renal failure (relative contraindication, requires careful monitoring and dose adjustment).
## Adverse Effects
* **Common:** Flushing, warmth, sweating, nausea, vomiting, hypotension, bradycardia, hyporeflexia, drowsiness, muscle weakness.
* **Serious:** Respiratory depression, cardiac arrest, hypermagnesemia (especially with renal impairment).
## Key Drug Interactions
* **Nondepolarizing Neuromuscular Blockers:** May potentiate neuromuscular blockade.
* **Calcium Salts:** May antagonize the effects of magnesium.
* **Tetracyclines and Quinolones:** May decrease absorption of these antibiotics if administered concurrently due to chelation. Separate administration by at least 2-3 hours.
## Monitoring
* **Vital Signs:** Blood pressure, heart rate, respiratory rate, deep tendon reflexes.
* **Serum Magnesium Levels:** Monitor frequently, especially during loading doses and continuous infusions. Target levels vary by indication.
* **Renal Function:** Serum creatinine and BUN, especially in patients with known or suspected renal impairment.
* **Urine Output:** Maintain adequate urine output.
## Clinical Pearls
* Magnesium sulfate is administered as a 50% solution (500 mg/mL).
* When administered IV, it should be diluted and infused slowly to prevent hypotension and cardiovascular depression.
* Monitor for signs of magnesium toxicity: absent deep tendon reflexes, decreased respiratory rate, altered mental status, hypotension, and cardiac arrhythmias.
* In patients with torsades de pointes, prompt administration can be life-saving.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for clinical judgment. Always consult the most current prescribing information and relevant institutional protocols before administering magnesium sulfate.
