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# Magnesium Sulphate
## Overview
Magnesium sulphate is a parenteral mineral supplement and electrolyte primarily used for rapid correction of hypomagnesemia, management of eclampsia/preeclampsia, and as an adjunct in severe asthma exacerbations. It acts as a physiological calcium antagonist and neuromuscular blocker.
## Primary Indications
* **Hypomagnesemia:** Replacement for symptomatic or severe deficiency.
* **Obstetrics:** Prevention/treatment of seizures in eclampsia and severe preeclampsia.
* **Pulmonary:** Adjunct therapy for life-threatening or severe acute asthma exacerbations.
* **Arrhythmias:** First-line for Torsades de Pointes.
## Adult Dosing
* **Hypomagnesemia (Severe/Symptomatic):** 1–2 g (IV/IM) over 5–60 minutes. May repeat as needed based on serum levels.
* **Eclampsia/Preeclampsia:** Loading dose of 4–6 g IV over 15–20 minutes, followed by a continuous infusion of 1–2 g/hour. Continue for 24 hours postpartum.
* **Torsades de Pointes:** 1–2 g IV bolus over 5–20 minutes; may repeat once if rhythm persists.
* **Severe Asthma:** 2 g IV infusion over 20 minutes (single dose).
## Pediatric Dosing
* **Hypomagnesemia:** 25–50 mg/kg/dose (IV) every 6 hours for 3–4 doses. Maximum: 2 g/dose.
* **Severe Asthma:** 25–75 mg/kg (IV) over 20 minutes. Maximum: 2 g/dose.
## Dose Adjustments
* **Renal Impairment:** Reduce dose and frequency in patients with renal failure (CrCl <30 mL/min). Risk of toxicity is significantly increased. Monitor serum levels closely.
## Contraindications
* Heart block or myocardial damage.
* Severe renal impairment (use with extreme caution/reduction).
* Hypocalcemia.
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, transient bradycardia.
* **Severe (Toxicity):** Loss of deep tendon reflexes (first sign of toxicity), respiratory depression, cardiac arrest, AV block.
## Key Drug Interactions
* **Neuromuscular Blockers:** Potentiates effect (leads to prolonged paralysis).
* **Calcium Channel Blockers:** High risk of profound hypotension.
* **Aminoglycoside Antibiotics:** Increased risk of neuromuscular blockade.
* **Digoxin:** Potential for increased susceptibility to digitalis toxicity if magnesium is depleted.
## Monitoring
* **Toxicity:** Monitor deep tendon reflexes (DTRs), respiratory rate (must be >16 breaths/min), and urine output (>30 mL/hr) during continuous infusion.
* **Serum Levels:** Monitor serum magnesium levels (Target: 1.7–2.3 mg/dL).
* **Calcium Gluconate:** Always have 1 gram of IV calcium gluconate at the bedside to reverse magnesium toxicity.
## Clinical Pearls
* **Administration:** IV rapid push is generally reserved for Torsades de Pointes. For other indications, slow infusion is preferred to avoid flushing and hypotension.
* **IM Injection:** Extremely painful. Reserves for cases where lack of IV access makes it mandatory.
* **Toxicity Reversal:** In the event of hypermagnesemia-induced respiratory depression, administer Calcium Gluconate 1g IV slowly.
* **General Note:** Dosing varies significantly by institutional protocol, particularly in obstetrics and pediatrics. Always consult local guidelines.
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*Disclaimer: This information is for educational purposes only. Always consult current institutional clinical guidelines, local formularies, and the drug manufacturer's prescribing information before ordering or administering medication.*
