Please check your internet connection and try again.
# Magnesium Sulphate
## Overview
Magnesium sulfate is an electrolyte that is essential for the normal functioning of cellular processes. It is available in intravenous (IV) and intramuscular (IM) formulations.
## Primary Indications
* **Hypomagnesemia:** Treatment of low magnesium levels.
* **Eclampsia/Preeclampsia:** Management and prevention of seizures associated with severe preeclampsia and eclampsia.
* **Torsades de Pointes:** Treatment of polymorphic ventricular tachycardia.
* **Bronchodilator:** Adjunctive therapy in severe bronchospasm (asthma).
## Adult Dosing
* **Hypomagnesemia:**
* **Acute/Severe:** 4-6 grams IV infusion over 5-60 minutes, followed by 1-2 grams/hour as a continuous infusion. Maximum continuous infusion rate generally 2 grams/hour.
* **Mild/Moderate:** 2-4 grams IM in divided doses every 4-12 hours for 2-4 days. Or 4-6 grams IV infusion over 5-60 minutes.
* **Eclampsia/Preeclampsia (loading dose):** 4-6 grams IV infusion over 15-20 minutes, followed by 1-2 grams/hour as a continuous infusion.
* **Eclampsia/Preeclampsia (alternative IM loading dose):** 5 grams IM in each buttock (total 10 grams) followed by 5 grams IM every 4 hours.
* **Torsades de Pointes:** 1-2 grams IV in 100 mL D5W infused over 5-10 minutes. May repeat if necessary. Subsequent infusions of 0.5-1 gram/hour may be given.
* **Bronchodilator (Adjunctive):** 1-2 grams IV infusion over 15-20 minutes.
Dosing may vary based on local protocols, especially for eclampsia/preeclampsia.
## Pediatric Dosing
* **Hypomagnesemia:**
* **IV:** 25-50 mg/kg/dose infused over 5-60 minutes. Maximum dose generally 2 grams. May repeat every 4-12 hours.
* **IM:** 25-50 mg/kg/dose every 4-12 hours.
* **Eclampsia/Preeclampsia:** Generally follows adult protocols, but specific pediatric guidelines may apply in severe cases or specific populations. Consult pediatric critical care guidelines.
* **Torsades de Pointes:** 25-50 mg/kg IV over 10-20 minutes, maximum 2 grams. May repeat once.
## Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. Use with caution and monitor serum magnesium levels closely in patients with impaired renal function. Reduced doses or discontinuation may be necessary.
## Contraindications
* Hypermagnesemia
* Heart block
* Myocardial infarction (acute)
* Duchenne muscular dystrophy (IV use)
## Adverse Effects
* **Common:** Flushing, hypotension, nausea, vomiting, somnolence, decreased deep tendon reflexes.
* **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, hypothermia, muscle weakness, hypermagnesemia.
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** Magnesium can potentiate neuromuscular blockade, leading to prolonged muscle paralysis.
* **Calcium Channel Blockers:** Additive hypotensive effects.
* **Tetracyclines and Quinolones:** Magnesium can decrease the absorption of oral formulations of these antibiotics. Separate administration by at least 2-3 hours.
* **Digoxin:** High doses of IV magnesium sulfate may increase the risk of digoxin toxicity.
## Monitoring
* **Serum Magnesium Levels:** Monitor frequently, especially with continuous infusions or in renal impairment. Target levels vary by indication (e.g., therapeutic range for eclampsia is typically 4-7 mEq/L).
* **Renal Function:** Monitor creatinine.
* **Deep Tendon Reflexes:** Assess for loss of reflexes (sign of toxicity).
* **Respiratory Rate:** Monitor for signs of respiratory depression.
* **Electrocardiogram (ECG):** Monitor for cardiac arrhythmias.
* **Blood Pressure:** Monitor for hypotension.
## Clinical Pearls
* IV magnesium sulfate must be administered slowly to avoid hypotension and respiratory depression.
* Always have calcium gluconate readily available as an antidote for magnesium toxicity.
* Monitor for signs and symptoms of magnesium toxicity: absent deep tendon reflexes, decreased respiratory rate, altered mental status, and hypotension.
* For oral administration (less common for acute indications), magnesium can cause diarrhea.
***
**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for complete and up-to-date details on drug use, including specific dosing, contraindications, interactions, and adverse effects, as recommendations may vary.
