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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral that plays a crucial role in numerous biochemical functions. It is available for intravenous (IV) and intramuscular (IM) administration.
## Primary Indications
* Treatment of hypomagnesemia.
* Prevention and treatment of seizures in preeclampsia and eclampsia.
* Treatment of torsades de pointes.
* Management of status asthmaticus.
## Adult Dosing
* **Hypomagnesemia:**
* Severe deficiency: 4-5 g (32-40 mEq) IV infused over 5-60 minutes, followed by 2-3 g (16-24 mEq) every 4-12 hours over 3-4 days.
* Less severe deficiency: 1-2 g (8-16 mEq) IV or IM every 6-12 hours for 3-5 days.
* **Preeclampsia/Eclampsia:**
* Loading dose: 4-6 g (32-48 mEq) IV infused over 5-20 minutes.
* Maintenance dose: 1-2 g/hour (8-16 mEq/hour) IV infusion. Some protocols may use intermittent IV or IM doses. Dosing can vary significantly based on local protocols.
* **Torsades de Pointes:** 1-2 g (8-16 mEq) IV diluted in 10 mL D5W and infused rapidly (e.g., over 5-10 minutes), followed by a continuous infusion of 0.5-1 g/hour (4-8 mEq/hour) if needed.
* **Status Asthmaticus:** 25-40 mg/kg (up to a maximum of 2 g) IV as a single dose over 15-30 minutes.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing is highly variable and depends on the severity of deficiency. Typical doses range from 25-100 mg/kg/dose (2-8 mEq/kg/dose) IV or IM every 4-12 hours.
* **Preeclampsia/Eclampsia:** Dosing is often based on adult protocols and adjusted for weight, but specific pediatric guidelines are less established and may follow local protocols.
* **Torsades de Pointes:** 25-50 mg/kg (up to a maximum of 2 g) IV as a single dose over 10-30 minutes.
* **Status Asthmaticus:** 25-40 mg/kg (up to a maximum of 2 g) IV as a single dose over 15-30 minutes.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduce dose and monitor serum magnesium levels closely. In severe renal impairment, avoid if possible.
## Contraindications
* Hypermagnesemia.
* Heart block.
* Myocardial infarction.
* Heart failure.
* A-V conduction disturbance.
## Adverse Effects
Common: Flushing, sweating, hypotension, nausea, vomiting, drowsiness.
Serious: Respiratory depression, cardiac arrest, hypermagnesemia (symptoms include absent deep tendon reflexes, hypotension, ECG changes, respiratory depression, cardiac arrest), hyperthermia.
## Key Drug Interactions
* **Nondepolarizing neuromuscular blockers:** Magnesium can potentiate neuromuscular blockade, leading to prolonged respiratory depression.
* **Calcium:** IV calcium may be used to counteract magnesium toxicity.
* **Certain antibiotics (e.g., aminoglycosides, tetracyclines):** Magnesium can potentiate their neuromuscular blocking effects.
## Monitoring
* **Serum magnesium levels:** Monitor at baseline, after loading doses, and periodically during infusions, especially in patients with renal impairment or those receiving prolonged therapy. Target levels for eclampsia treatment are typically 4-7 mEq/L.
* **Renal function:** Assess baseline and periodically.
* **Deep tendon reflexes:** Assess for loss of reflexes, an early sign of hypermagnesemia.
* **Respiratory rate and effort:** Monitor for signs of respiratory depression.
* **Cardiac rhythm:** Monitor ECG for changes.
* **Blood pressure:** Monitor for hypotension.
## Clinical Pearls
* Magnesium sulfate is a potent vasodilator and can cause hypotension, especially with rapid IV infusion.
* Always dilute magnesium sulfate for IV infusion.
* Monitor for signs of hypermagnesemia, particularly in patients with impaired renal function.
* Discontinuation of magnesium should be considered if deep tendon reflexes are lost or respiratory rate falls below 16 breaths/min.
* The goal for magnesium levels in preeclampsia/eclampsia is to achieve therapeutic levels while avoiding toxicity. Dosing may need to be individualized.
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***Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication. Verification of current drug information is essential.*
