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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral that plays a role in numerous enzymatic reactions. It is available in parenteral and oral formulations.
## Primary Indications
* **Hypomagnesemia:** Treatment of magnesium deficiency.
* **Eclampsia/Preeclampsia:** Prevention and treatment of seizures associated with hypertensive disorders of pregnancy.
* **Torsades de Pointes:** Treatment of polymorphic ventricular tachycardia.
* **Bronchospasm:** Adjunctive treatment in severe acute asthma exacerbations.
* **Constipation (Oral):** Osmotic laxative.
## Adult Dosing
* **Hypomagnesemia:**
* **Severe:** 4-6 g IV infusion over 5-60 minutes, followed by a continuous infusion of 1-2 g/hour. Dose may be adjusted based on serum magnesium levels.
* **Less Severe:** 1-2 g IV infusion over 5-60 minutes, followed by oral magnesium or a lower continuous infusion.
* **Oral:** 30-60 mEq (2.5-5 g) divided daily doses.
* **Eclampsia/Preeclampsia:** Loading dose of 4-6 g IV infused over 5-10 minutes, followed by a maintenance infusion of 1-2 g/hour. Dosing may vary by protocol.
* **Torsades de Pointes:** 1-2 g IV diluted in 10-50 mL D5W infused over 5-10 minutes. May repeat doses. Continuous infusion of 1 g/hour may be considered.
* **Bronchospasm:** 1-2 g IV infused over 15-30 minutes.
* **Constipation (Oral):** 10-30 mL of a 50% solution, or 2-4 tablets/capsules. Onset typically 30 minutes to 6 hours.
## Pediatric Dosing
Dosing is highly variable and often guided by protocol, serum magnesium levels, and indication.
* **Hypomagnesemia:**
* **Premature infants:** 25-50 mg/kg/dose IV every 12-24 hours.
* **Older infants/children:** 25-50 mg/kg/dose IV every 4-6 hours for 3-4 doses, or continuous infusion of 10-20 mg/kg/hour.
* **Eclampsia/Preeclampsia:** Dosing follows adult protocols, adjusted for weight if necessary.
* **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 g) over 10-20 minutes. Continuous infusion of 10-20 mg/kg/hour may be considered.
* **Bronchospasm:** 25-50 mg/kg IV (maximum 2 g) over 15-30 minutes.
## Dose Adjustments
* **Renal Impairment:** Reduce dose and monitor magnesium levels closely. Avoid in severe renal failure if possible.
## Contraindications
* Hypermagnesemia.
* Heart block (unless a pacemaker is present).
* Myocardial infarction.
* Hypersensitivity to magnesium sulfate.
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, nausea, vomiting, diarrhea (oral).
* **Serious:** Respiratory depression, bradycardia, cardiac arrest, hyporeflexia, neuromuscular blockade, hypermagnesemia (symptoms include lethargy, confusion, slurred speech, muscle weakness, decreased reflexes, ECG changes, hypotension, cardiac arrhythmias, respiratory arrest).
## Key Drug Interactions
* **Neuromuscular Blockers:** Increased neuromuscular blockade.
* **Calcium Salts:** May antagonize magnesium's effects.
* **Tetracyclines and Quinolones:** Oral magnesium can decrease absorption; separate administration by at least 2 hours.
## Monitoring
* **Magnesium Levels:** Regularly monitor serum magnesium, especially with IV infusions and in patients with renal impairment. Therapeutic range for hypomagnesemia treatment is typically 2-4 mEq/L.
* **Renal Function:** Monitor creatinine and BUN.
* **Vital Signs:** Blood pressure, heart rate, respiratory rate.
* **Neurological Status:** Deep tendon reflexes.
* **Cardiac Monitoring:** ECG, especially with IV administration.
## Clinical Pearls
* Magnesium sulfate is a smooth muscle relaxant and can cause vasodilation, leading to hypotension. Administer IV doses slowly and monitor blood pressure.
* Monitor deep tendon reflexes; loss of reflexes indicates hypermagnesemia.
* Ensure adequate hydration and electrolyte balance, especially in patients with diarrhea from oral magnesium.
* Calcium gluconate is the antidote for severe hypermagnesemia.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and relevant clinical guidelines for the most up-to-date and comprehensive information before prescribing or administering any medication.*
