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# Magnesium Sulphate
## Overview
Magnesium sulphate is an essential mineral that plays a vital role in numerous biochemical functions. It is available in intravenous (IV) and intramuscular (IM) formulations.
## Primary Indications
* Treatment of hypomagnesemia.
* Management of eclampsia and pre-eclampsia.
* Treatment of torsades de pointes.
* Management of severe bronchospasm (off-label).
## Adult Dosing
* **Hypomagnesemia:**
* Severe: 4-6 g IV infused over 5-60 minutes, followed by a continuous infusion of 1-2 g/hour.
* IM: 1-4 g IM every 4 hours as needed.
* **Eclampsia/Pre-eclampsia (Treatment):** 4-6 g IV loading dose over 5-20 minutes, followed by a continuous infusion of 1-2 g/hour. Local protocols may vary.
* **Torsades de Pointes:** 1-2 g IV in 10 mL dextrose 5% or normal saline over 5-10 minutes. May repeat. Followed by infusion of 1-2 g/hour.
* **Severe Bronchospasm (Asthma):** 1-2 g IV infusion over 15-30 minutes.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing varies significantly by age and severity. A common regimen for severe hypomagnesemia is an initial IV dose of 25-50 mg/kg (maximum 2 g) over 30-60 minutes, followed by an infusion of 10-30 mg/kg/hour (maximum 1 g/day). Consult specific pediatric guidelines.
* **Eclampsia/Pre-eclampsia:** Not typically used in pediatric patients for this indication.
* **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 g) over 10-20 minutes.
## Dose Adjustments
* **Renal Impairment:** Use with extreme caution. Magnesium is renally excreted. Dose reduction and careful monitoring are essential. Avoid use in severe renal impairment if possible.
## Contraindications
* Hypermagnesemia.
* Heart block (unless a pacemaker is present).
* Myocardial infarction (caution).
* Hypersensitivity to magnesium sulphate.
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, nausea, vomiting, somnolence.
* **Serious:** Respiratory depression, cardiac arrhythmias, loss of deep tendon reflexes, muscle weakness, decreased urine output, hypermagnesemia.
## Key Drug Interactions
* **Neuromuscular Blockers:** Magnesium can potentiate neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of hypotension and cardiac depression.
* **Nifedipine:** Increased risk of hypotension.
* **Digoxin:** High doses of magnesium may worsen digoxin toxicity in certain contexts.
## Monitoring
* **Magnesium levels:** Prior to and during therapy, especially with prolonged infusions or in renal impairment. Therapeutic range typically 1.7-2.2 mmol/L (4-5.5 mg/dL) for hypomagnesemia treatment, but goals may differ for eclampsia.
* **Renal function (serum creatinine, BUN).**
* **Deep tendon reflexes:** Assess for loss of reflexes.
* **Respiratory rate:** Monitor for depression.
* **Blood pressure and heart rate.**
* **Urine output.**
## Clinical Pearls
* IV administration is generally preferred for acute management of severe hypomagnesemia and eclampsia due to rapid onset and better titration.
* IM injections can be painful and cause tissue irritation; rotate injection sites.
* Magnesium sulphate is a central nervous system depressant and a vasodilator.
* Monitor for signs and symptoms of hypermagnesemia, particularly in patients with impaired renal function.
* Calcium gluconate (IV) is the antidote for magnesium toxicity.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and clinical guidelines before making any treatment decisions.
