Please check your internet connection and try again.
# Magnesium Sulphate
## Overview
Magnesium sulphate is an electrolyte that plays a role in numerous enzymatic reactions, neuromuscular transmission, and cardiac excitability.
## Primary Indications
* Hypomagnesemia
* Preeclampsia and Eclampsia (tocolytic and anticonvulsant)
* Torsades de Pointes
* Bronchodilator (adjunctive in severe asthma exacerbations)
## Adult Dosing
* **Hypomagnesemia:**
* **Severe (symptomatic or serum Mg < 1.0 mg/dL):** 4-6 grams intravenously (IV) over 5-10 minutes, followed by 1-2 grams per hour by continuous IV infusion. Dose adjusted to maintain serum magnesium between 2-3 mg/dL.
* **Mild-to-moderate (asymptomatic or serum Mg 1.0-1.5 mg/dL):** 4 grams IV in divided doses over several hours.
* **Preeclampsia/Eclampsia:** Loading dose of 4-6 grams IV over 5-20 minutes. Maintenance infusion of 1-2 grams per hour. Dose adjusted based on clinical response and magnesium levels.
* **Torsades de Pointes:** 1-2 grams IV in 50-100 mL dextrose 5% in water over 5-10 minutes. May repeat every 5-15 minutes. Consider continuous infusion of 0.5-1 gram per hour.
* **Asthma (adjunctive):** 1-2 grams IV infusion over 15-20 minutes.
## Pediatric Dosing
* **Hypomagnesemia:**
* **Severe:** 25-50 mg/kg/dose IV over 10-30 minutes. Maximum 2 grams per dose. May repeat every 4 hours as needed. For continuous infusion, 100-200 mg/kg/day (max 2 g/day) divided every 6-8 hours or as a continuous infusion.
* **Mild-to-moderate:** 25 mg/kg/dose IV over 10-30 minutes.
* **Eclampsia:** Dosing is highly variable and dependent on institutional protocols. Often guided by adult protocols with careful monitoring.
* **Asthma (adjunctive):** 25-75 mg/kg/dose IV over 10-30 minutes. Maximum 2 grams per dose.
Dosing for specific indications in pediatrics may vary significantly based on patient age, weight, renal function, and local protocols.
## Dose Adjustments
* **Renal Impairment:** Use with extreme caution. Reduce dose and monitor magnesium levels closely. Significant accumulation can occur in severe renal impairment. Dialysis may be required.
## Contraindications
* Hypermagnesemia
* Heart block
* Myocardial infarction
* Shock
## Adverse Effects
* **Common:** Flushing, warmth, hypotension, decreased deep tendon reflexes, somnolence, respiratory depression.
* **Severe:** Cardiac arrhythmias, cardiac arrest, loss of deep tendon reflexes, absent respirations, coma, hyperthermia.
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** Potentiates neuromuscular blockade.
* **Calcium Channel Blockers:** Increased risk of hypotension and bradycardia.
* **Nifedipine:** Additive hypotensive effects.
* **Tetracyclines and Quinolones:** Magnesium can decrease absorption; administer at least 2 hours before or 4-6 hours after these antibiotics.
## Monitoring
* **Serum Magnesium Levels:** Essential, especially with IV infusions, renal impairment, and prolonged use. Target levels vary by indication.
* **Renal function (BUN, Creatinine):** To assess risk of accumulation.
* **Deep tendon reflexes:** Assess for signs of toxicity.
* **Respiratory rate and pattern:** Monitor for respiratory depression.
* **Blood pressure and heart rate:** Monitor for hypotension and bradycardia.
* **Urine output:** Monitor for adequate renal function.
## Clinical Pearls
* IV magnesium is a vesicant; monitor IV site closely for extravasation.
* Calcium gluconate or calcium chloride should be readily available as an antidote for severe magnesium toxicity.
* The therapeutic effect of magnesium in preeclampsia/eclampsia is thought to be due to vasodilation and reduction of neuronal excitability.
* In asthma, magnesium may act as a bronchodilator by blocking smooth muscle contraction and inhibiting acetylcholine release.
***
*This information is intended for clinical use and does not substitute for professional medical judgment. Always consult the most current prescribing information and institutional protocols before administering this medication.*
