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# Magnesium Sulphate
## Overview
Magnesium sulphate is an essential mineral that plays a role in numerous enzymatic reactions, neuromuscular transmission, and cardiac function. It is available for intravenous and intramuscular administration.
## Primary Indications
* Treatment of hypomagnesemia.
* Prevention and treatment of eclampsia in pregnant patients.
* Management of torsades de pointes.
* Adjunctive therapy in severe asthma exacerbations.
## Adult Dosing
* **Hypomagnesemia:** 1-2 grams (8-16 mEq) of magnesium sulphate IV infused over 5-60 minutes, followed by 1 gram (8 mEq) every hour as needed, up to a maximum of 4 grams (32 mEq) in 24 hours. Alternatively, 4-5 grams (32-40 mEq) IM in divided doses every 4 hours.
* **Eclampsia:** 4 grams (32 mEq) of magnesium sulphate IV load infused over 5 minutes, followed by a continuous infusion of 1-2 grams (8-16 mEq) per hour. Maintenance IM dosing may be used per local protocol.
* **Torsades de Pointes:** 1-2 grams (8-16 mEq) of magnesium sulphate IV infused over 5-20 minutes. Repeat doses may be administered.
* **Asthma Exacerbation:** 1-2 grams (8-16 mEq) of magnesium sulphate IV infused over 15-30 minutes.
Dosing for specific indications may vary based on clinical guidelines and institutional protocols.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing is weight-based and often guided by serum magnesium levels and local protocols. A common initial IV dose is 25-50 mg/kg (0.1-0.2 mEq/kg) infused over 10-30 minutes, not to exceed 2 grams (16 mEq). Subsequent doses vary.
* **Eclampsia:** Dosing follows adult protocols, but may be adjusted based on weight and renal function per specialist guidance.
## Dose Adjustments
* **Renal Impairment:** Magnesium sulphate should be used with caution in patients with impaired renal function. Dose reduction and increased monitoring are necessary, especially in severe renal impairment.
## Contraindications
* Heart block.
* Myocardial infarction (acute phase).
* Hypermagnesemia.
* Hypocalcemia.
## Adverse Effects
Common adverse effects include flushing, hypotension, nausea, vomiting, and somnolence. More severe effects include respiratory depression, cardiac arrhythmias, and loss of deep tendon reflexes.
## Key Drug Interactions
* **Calcium Channel Blockers:** Increased risk of hypotension and cardiac conduction abnormalities.
* **Neuromuscular Blockers:** May potentiate neuromuscular blockade.
* **Potassium-sparing Diuretics:** Increased risk of hypermagnesemia.
## Monitoring
* Serum magnesium levels (especially with repeated or high-dose administration).
* Deep tendon reflexes.
* Respiratory rate and depth.
* Blood pressure.
* Urine output.
* Cardiac rhythm (especially in patients with pre-existing cardiac conditions or receiving high doses).
## Clinical Pearls
* Rapid IV infusion can lead to hypotension and flushing.
* Monitor for signs of magnesium toxicity, including absent reflexes, decreased respiratory rate, and altered mental status.
* Magnesium sulphate is a calcium antagonist; therefore, calcium administration may be necessary in cases of toxicity.
* Ensure adequate hydration and renal function when administering magnesium sulphate.
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*This information is intended for healthcare professionals and does not replace the need to consult the most current prescribing information and relevant clinical guidelines.*
