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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral that plays a role in numerous physiological processes, including muscle and nerve function, blood glucose control, and blood pressure regulation. It is available in oral and intravenous formulations.
## Primary Indications
* **Hypomagnesemia:** Treatment and prevention of magnesium deficiency.
* **Eclampsia and Preeclampsia:** Prevention and treatment of seizures in pregnant patients.
* **Torsades de Pointes:** Treatment of this specific type of polymorphic ventricular tachycardia.
* **Bronchodilation:** Adjunctive therapy in severe asthma exacerbations.
* **Constipation (Oral):** Laxative effect.
## Adult Dosing
* **Hypomagnesemia (IV):**
* **Severe deficiency (<1 mg/dL):** 4-6 grams IV initially, followed by 2-4 grams IV every 4-12 hours as needed. Total daily dose should not exceed 30-40 grams.
* **Less severe deficiency (1-1.7 mg/dL):** 1-2 grams IV every 4-12 hours.
* **Maintenance (IV):** 4-6 grams IV infused over 24 hours.
* **Eclampsia/Preeclampsia (IV):**
* **Loading Dose:** 4-6 grams IV infused over 5-10 minutes.
* **Maintenance Dose:** 1-2 grams/hour IV infusion.
* **Torsades de Pointes (IV):** 1-2 grams IV diluted in 100 mL D5W infused over 5-10 minutes. May repeat dose and follow with continuous infusion of 0.5-1 gram/hour.
* **Asthma Exacerbation (IV):** 1-2 grams IV diluted in 50-100 mL NS or D5W infused over 15-30 minutes.
* **Constipation (Oral):** 30 mL of a 50% solution, or 2-6 grams of oral powder, as a single dose.
## Pediatric Dosing
Dosing for pediatric patients is highly variable and often determined by weight and clinical indication. **Consult specific pediatric guidelines or protocols.**
* **Hypomagnesemia (IV):** Typical doses range from 25-50 mg/kg per dose, not to exceed adult maximums.
* **Eclampsia/Preeclampsia (IV):** Dosing typically follows adult regimens, adjusted for weight.
* **Asthma Exacerbation (IV):** Typically 25-50 mg/kg IV infused over 15-30 minutes.
## Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. In patients with impaired renal function, reduce the dose and monitor serum magnesium levels closely to prevent hypermagnesemia.
## Contraindications
* Hypermagnesemia.
* Myocardial conduction disturbance.
* Heart block.
* Active labor (when used for preeclampsia/eclampsia, the benefits generally outweigh risks, but caution is advised).
* Severe renal failure.
## Adverse Effects
* **Common:** Flushing, hypotension, drowsiness, nausea, vomiting, diarrhea (oral).
* **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, loss of deep tendon reflexes, neuromuscular blockade, hypermagnesemia.
## Key Drug Interactions
* **Neuromuscular Blockers:** Increased neuromuscular blockade and respiratory depression.
* **Calcium Channel Blockers:** Additive hypotensive effects.
* **Tetracyclines and Fluoroquinolones:** Magnesium can decrease the absorption of these antibiotics; administer them at least 2 hours before or 4-6 hours after magnesium.
## Monitoring
* **Serum Magnesium Levels:** Monitor frequently, especially with IV administration and in patients with renal impairment. Therapeutic range for IV magnesium is generally 4-7 mg/dL.
* **Renal function (BUN, creatinine).**
* **Deep tendon reflexes.**
* **Respiratory rate and depth.**
* **Blood pressure and heart rate.**
* **Urine output.**
## Clinical Pearls
* IV magnesium sulfate should be administered slowly to avoid hypotension and flushing.
* Always dilute IV magnesium sulfate before administration.
* Calcium (e.g., calcium gluconate 1 gram IV) is the antidote for magnesium toxicity.
* Oral magnesium sulfate may cause significant diarrhea due to its osmotic effect.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and relevant clinical guidelines for complete details and to verify current recommendations before making treatment decisions.*
