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# Magnesium Sulphate
## Overview
Magnesium sulphate is an electrolyte replacement and anticonvulsant medication. It is essential for numerous biochemical functions, including nerve and muscle function, cardiac rhythm, and bone health.
## Primary Indications
* Treatment of hypomagnesemia
* Prevention and treatment of seizures in preeclampsia and eclampsia
* Management of torsades de pointes
* Treatment of status asthmaticus (adjunctive therapy)
* Management of severe hypokalemia (when potassium replacement alone is insufficient)
## Adult Dosing
* **Hypomagnesemia:**
* **Severe deficiency:** 4-5 grams (32-40 mEq) IV infused over 5-60 minutes, followed by a continuous infusion of 1-2 grams (8-16 mEq) per hour. Alternatively, 1 gram (8 mEq) IM every 6 hours for 4 doses.
* **Mild to moderate deficiency:** 1-2 grams (8-16 mEq) IV or IM, followed by maintenance doses as needed.
* **Preeclampsia/Eclampsia:** Loading dose: 4-6 grams (32-48 mEq) IV infused over 5-10 minutes. Maintenance dose: 1-2 grams (8-16 mEq) per hour IV infusion. Dosing may vary significantly based on local protocol and patient response.
* **Torsades de Pointes:** 1-2 grams (8-16 mEq) IV bolus, followed by 0.5-1 gram (4-8 mEq) per hour infusion.
* **Status Asthmaticus:** 2 grams (16 mEq) IV infused over 15-20 minutes.
* **Severe Hypokalemia:** 4 grams (32 mEq) IV in 1 liter of IV fluid over 10-20 minutes.
## Pediatric Dosing
* **Hypomagnesemia:** 25-50 mg/kg/dose (0.2-0.4 mEq/kg/dose) IV or IM every 4-6 hours as needed. Maximum dose not well established; consult specific protocols.
* **Preeclampsia/Eclampsia:** Dosing is highly variable and often follows adult protocols adapted for weight. Specific pediatric protocols should be consulted.
* **Status Asthmaticus:** 25-40 mg/kg IV over 15-30 minutes. Maximum dose typically 2 grams.
## Dose Adjustments
Dose reduction is recommended in patients with impaired renal function. Monitor serum magnesium levels and renal function closely.
## Contraindications
* Hypermagnesemia
* Heart block or myocardial damage
* Hypersensitivity to magnesium sulphate
## Adverse Effects
Common: Flushing, sweating, hypotension, nausea, vomiting, decreased deep tendon reflexes, respiratory depression.
Serious: Cardiac arrhythmias, cardiac arrest, respiratory paralysis, hypermagnesemia (especially with renal impairment).
## Key Drug Interactions
* **Neuromuscular Blockers:** May potentiate neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of hypotension and bradycardia.
* **Certain Antibiotics (e.g., aminoglycosides, tetracyclines):** May impair neuromuscular transmission.
* **Nifedipine:** Increased risk of hypotension.
## Monitoring
* **Serum Magnesium Levels:** Crucial for guiding dosing and preventing toxicity. Target levels vary by indication.
* **Renal Function:** Assess BUN, creatinine, and urine output, especially in patients with impaired renal function.
* **Vital Signs:** Blood pressure, heart rate, respiratory rate.
* **Deep Tendon Reflexes:** Assess for presence and symmetry; diminished reflexes can indicate toxicity.
* **Cardiac Rhythm:** Continuous ECG monitoring may be necessary, particularly with IV infusions or in patients at risk for arrhythmias.
* **Urine Output:** Important for assessing renal function.
## Clinical Pearls
* Magnesium sulphate can cause flushing and a sensation of warmth. Administer IV infusions slowly to minimize these effects and prevent hypotension.
* In eclampsia, magnesium sulphate is generally preferred over diazepam for seizure control due to a better maternal and neonatal safety profile.
* Always verify the concentration of magnesium sulphate solutions before administration, especially for IV infusion.
* Rapid IV administration can lead to cardiac arrest.
* For IM administration, divide doses between two sites to reduce pain and induration.
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*Please consult the most current prescribing information and relevant institutional protocols for complete and up-to-date drug information.*
