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# Magnesium Sulphate
## Overview
Magnesium sulphate is an electrolyte supplement and anticonvulsant. It is available for intravenous (IV) and intramuscular (IM) administration.
## Primary Indications
* Treatment of hypomagnesemia.
* Prevention and treatment of seizures in preeclampsia and eclampsia.
* Management of status epilepticus refractory to other agents.
* Management of torsades de pointes.
## Adult Dosing
* **Hypomagnesemia:**
* Mild deficiency: 1 gram IV every 6 hours for 4 doses.
* Severe deficiency: 4 grams IV initially, followed by 1-2 grams per hour infusion, or 1 gram IM every 4 hours for 4 doses. Dosing should be guided by serum magnesium levels and clinical response. Maximum infusion rate typically 1-2 grams/hour.
* **Preeclampsia/Eclampsia:**
* Loading dose: 4-6 grams IV over 5-20 minutes.
* Maintenance infusion: 1-2 grams per hour. Alternatively, 5 grams IM into each buttock every 4 hours.
* Continue for at least 24 hours after delivery or 24 hours after seizure cessation, whichever is longer.
* **Torsades de Pointes:** 1-2 grams IV, followed by 0.5-1 gram/hour infusion if needed.
* **Status Epilepticus (Refractory):** 2-4 grams IV over 10-20 minutes.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing varies significantly based on age and clinical condition. Common recommendations range from 20-50 mg/kg/dose IV or IM every 6-12 hours. Doses up to 100 mg/kg have been used in severe cases. Consult specialized pediatric resources for precise dosing.
* **Eclampsia:** Similar to adults, but dosing may be adjusted based on weight. Loading doses of 40 mg/kg (max 2 grams) followed by a continuous infusion of 20 mg/kg/hr (max 1 gram/hr).
## Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. Reduce dose and monitor serum magnesium levels closely in patients with impaired renal function. Discontinuation may be necessary in severe renal failure.
## Contraindications
* Hypermagnesemia.
* Heart block (unless a pacemaker is present).
* Myocardial infarction (acute).
* Hypersensitivity to magnesium sulphate.
* Severe renal impairment.
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, nausea, vomiting, drowsiness, decreased deep tendon reflexes.
* **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, hypermagnesemia (especially with renal impairment).
## Key Drug Interactions
* **Neuromuscular Blockers:** Magnesium can potentiate neuromuscular blockade, leading to prolonged respiratory depression.
* **Calcium Channel Blockers:** Additive hypotensive effects.
* **Digoxin:** Increased risk of digoxin toxicity.
## Monitoring
* Serum magnesium levels.
* Respiratory rate and depth.
* Deep tendon reflexes.
* Blood pressure.
* Urine output.
* Renal function.
## Clinical Pearls
* Administer IV infusions slowly to avoid hypotension and flushing.
* Have calcium gluconate readily available as an antidote for magnesium toxicity.
* Monitor for signs of hypermagnesemia, particularly in patients with renal insufficiency.
* Discontinue infusion if respiratory rate falls below 16 breaths/min or deep tendon reflexes are lost.
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*Disclaimer: This information is intended for healthcare professionals. Always verify current prescribing information and local protocols before administering any medication.*
