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# Magnesium Sulfate
## Overview
Magnesium sulfate is an electrolyte that plays a vital role in numerous biochemical reactions. It is available for intravenous and intramuscular administration.
## Primary Indications
* Treatment of hypomagnesemia.
* Prevention and treatment of seizures in preeclampsia and eclampsia.
* Management of torsades de pointes.
* Treatment of bronchospasm in severe asthma exacerbations.
## Adult Dosing
* **Hypomagnesemia:**
* **Severe (serum magnesium < 1.3 mg/dL):** 4-6 grams IV infused over 5-60 minutes, followed by a continuous infusion of 1-2 grams/hour. The total daily dose should not exceed 30 grams.
* **Less Severe (serum magnesium 1.3-1.7 mg/dL):** 2-4 grams IV infused over 5-60 minutes. Maintenance doses may be required.
* **Preeclampsia/Eclampsia:**
* **Loading dose:** 4-6 grams IV infused over 5-20 minutes.
* **Maintenance dose:** 1-2 grams/hour IV infusion, or 4 grams IM every 4 hours.
* **Torsades de Pointes:** 1-2 grams IV bolus in 10-20 mL of D5W over 5-10 minutes, followed by a continuous infusion of 0.5-1 gram/hour.
* **Asthma Exacerbation:** 1-2 grams IV infused over 15-30 minutes.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing varies significantly based on age and serum magnesium level. Typical doses range from 20-50 mg/kg/dose IV, infused over 5-60 minutes, with a maximum single dose of 2 grams. Higher doses or continuous infusions may be used for severe cases. Consult specific pediatric guidelines.
* **Eclampsia:** 40 mg/kg IV loading dose, followed by 10-15 mg/kg/hour infusion. Maximum loading dose 2 grams.
* **Asthma Exacerbation:** 25-40 mg/kg IV infused over 15-30 minutes, maximum 2 grams.
## Dose Adjustments
Dose adjustments are necessary in patients with renal impairment. Avoid use in severe renal insufficiency if possible.
## Contraindications
* Hypermagnesemia.
* Heart block.
* Myocardial infarction.
* Hypotension.
* Severe renal impairment.
## Adverse Effects
Common adverse effects include flushing, hypotension, nausea, vomiting, and somnolence. Serious adverse effects include respiratory depression, cardiac arrhythmias, and hypermagnesemia (manifesting as loss of deep tendon reflexes, decreased respiratory rate, hypotension, and cardiac arrest).
## Key Drug Interactions
* **Neuromuscular blocking agents:** Magnesium sulfate can potentiate neuromuscular blockade, leading to increased muscle weakness and respiratory depression.
* **Calcium:** Concurrent administration of calcium may antagonize the cardiac effects of magnesium.
## Monitoring
* Serum magnesium levels.
* Blood pressure.
* Respiratory rate.
* Deep tendon reflexes.
* Urine output.
* Cardiac rhythm.
## Clinical Pearls
* Rapid IV infusion can cause hypotension and cardiac depression.
* Monitor for signs of hypermagnesemia, especially in patients with renal impairment or receiving high doses.
* Intramuscular administration can be painful; consider mixing with lidocaine if administered IM.
* Ensure calcium gluconate is readily available as an antidote for severe hypermagnesemia.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and local protocols before administering any medication.*
