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# Magnesium Sulphate
## Overview
Magnesium sulphate is an inorganic salt containing magnesium and sulphate ions. It is administered intravenously or intramuscularly for various medical conditions.
## Primary Indications
* Treatment of hypomagnesemia.
* Management of eclampsia and pre-eclampsia.
* Management of torsades de pointes.
* Adjunctive therapy for bronchospasm in severe asthma.
* Management of severe hypokalemia.
## Adult Dosing
* **Hypomagnesemia:**
* Severe: 4-6 grams IV infused over 10-60 minutes, followed by 1-2 grams per hour by continuous infusion.
* Mild/Moderate: 1-2 grams IM or IV infused over 5-10 minutes every 4-6 hours as needed.
* **Eclampsia/Pre-eclampsia:** Loading dose: 4-6 grams IV infused over 15-20 minutes. Maintenance infusion: 1-2 grams per hour. Total daily dose should not exceed 30-40 grams. Protocols may vary.
* **Torsades de Pointes:** 1-2 grams IV infused over 1-5 minutes. May repeat in 5-15 minutes. Continuous infusion of 0.5-1 gram per hour may be needed.
* **Bronchospasm (Adjunctive):** 1-2 grams IV infused over 15-20 minutes.
* **Hypokalemia (Severe):** Dosing varies significantly based on potassium and magnesium levels; consult specific protocols.
## Pediatric Dosing
* **Hypomagnesemia:** 20-50 mg/kg/dose IV infused over 10-30 minutes. Maximum single dose: 2 grams. May repeat every 4-12 hours.
* **Eclampsia:** Dosing is complex and often guided by institutional protocols. Generally, lower doses than adults are used.
* **Torsades de Pointes:** 25-50 mg/kg IV infused over 10-30 minutes. Maximum dose: 2 grams. May repeat.
* **Bronchospasm:** 25-50 mg/kg IV infused over 15-30 minutes. Maximum dose: 2 grams.
Dosing in pediatrics often requires specific institutional protocols and close monitoring due to variability in response and risk of toxicity.
## Dose Adjustments
* **Renal Impairment:** Use with extreme caution. Magnesium is renally excreted. Dose reduction and increased monitoring are necessary. Avoid if creatinine clearance is less than 30 mL/min.
* **Hepatic Impairment:** No dose adjustment is typically required, but caution is advised as hepatic dysfunction can sometimes affect magnesium balance.
## Contraindications
* Hypermagnesemia.
* Heart block.
* Myocardial infarction.
* Hyperkalemia.
* Shock.
* Severe renal failure (contraindicated for some indications).
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, nausea, vomiting, hyporeflexia, drowsiness.
* **Serious:** Respiratory depression, cardiac arrest, loss of deep tendon reflexes, extreme muscle weakness, hyperthermia, arrhythmias.
## Key Drug Interactions
* **Neuromuscular Blockers:** Potentiates neuromuscular blockade, increasing the risk of respiratory depression.
* **Calcium Channel Blockers:** Additive hypotensive effects and risk of bradycardia.
* **Digitalis Glycosides:** Risk of digitalis toxicity if hypomagnesemia is corrected without addressing hypokalemia.
* **Tetracyclines and Quinolones:** Magnesium can decrease the absorption of these antibiotics; administer them at least 2 hours before or 4-6 hours after magnesium.
## Monitoring
* **Magnesium levels:** Monitor serum magnesium levels (aim for 4-7 mEq/L for eclampsia; 1.5-2.5 mEq/L for hypomagnesemia).
* **Renal function:** Monitor urine output and serum creatinine.
* **Neurological status:** Assess deep tendon reflexes, mental status, and respiratory rate.
* **Cardiac rhythm:** Monitor ECG for changes, especially with higher doses or rapid infusion.
* **Blood pressure:** Monitor for hypotension.
## Clinical Pearls
* Rapid IV infusion can cause hypotension, flushing, and cardiac arrhythmias. Infuse slowly.
* Loss of deep tendon reflexes typically precedes respiratory depression and indicates toxicity.
* Magnesium sulphate administration can potentially mask or exacerbate hypokalemia. Monitor potassium levels closely.
* In eclampsia, therapeutic magnesium levels are typically higher than those used for simple magnesium replacement.
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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 institutional protocols before administering any medication.*
