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# Magnesium Sulfate
## Overview
Magnesium sulfate is an essential mineral that plays a role in numerous physiological processes, including neuromuscular function, cardiac rhythm, and enzyme activity.
## Primary Indications
* **Hypomagnesemia:** Treatment of low magnesium levels.
* **Eclampsia/Preeclampsia:** Prevention and treatment of seizures in pregnant women with severe preeclampsia or eclampsia.
* **Torsades de Pointes:** Treatment of polymorphic ventricular tachycardia (Torsades de Pointes).
* **Bronchodilator:** Adjunctive therapy in severe asthma exacerbations.
## Adult Dosing
* **Hypomagnesemia:**
* **Severe/Symptomatic:** 4-5 g (32-40 mEq) IV infused over 5-15 minutes, followed by a continuous infusion of 1-2 g (8-16 mEq) per hour. Maintenance dose typically 4-6 g (32-48 mEq) IV over 24 hours.
* **Asymptomatic:** 1-2 g (8-16 mEq) IV infused over 1-2 hours, or 5-10 g (40-80 mEq) IM divided into two doses every 4 hours.
* **Eclampsia/Preeclampsia (ACLS Protocol):** 4-6 g (32-48 mEq) IV bolus over 5-10 minutes, followed by a continuous infusion of 1-2 g (8-16 mEq) per hour. Alternatively, 5 g (40 mEq) IM in each buttock for initial dose, followed by 5 g (40 mEq) IM into alternating buttocks every 4 hours.
* **Torsades de Pointes:** 1-2 g (8-16 mEq) IV infused over 1-5 minutes. May repeat in 5-15 minutes. Further doses can be given as an infusion of 0.5-1 g (4-8 mEq) per hour.
* **Asthma Exacerbation (Adjunctive):** 1-2 g (8-16 mEq) IV infused over 15-20 minutes.
## Pediatric Dosing
Dosing in pediatrics is highly variable and often guided by local protocols and serum magnesium levels.
* **Hypomagnesemia:** 25-50 mg/kg (0.2-0.4 mEq/kg) IV infused over 30-60 minutes. Maximum dose typically 2 g (16 mEq).
* **Eclampsia:** Dosing varies; often similar to adult dosing based on weight or use of specific pediatric protocols.
## Dose Adjustments
* **Renal Impairment:** Use with caution. Reduce dose and monitor magnesium levels closely. Accumulation can occur.
## Contraindications
* Hypermagnesemia.
* Heart block.
* Myocardial infarction (in some cases, especially if conduction abnormalities are present).
* Intestinal obstruction or perforation (for oral magnesium).
## Adverse Effects
* **Common:** Flushing, hypotension, nausea, vomiting, diarrhea (oral), lethargy, decreased deep tendon reflexes.
* **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, hypermagnesemia (especially in renal impairment).
## Key Drug Interactions
* **Neuromuscular Blockers:** May potentiate neuromuscular blockade.
* **Calcium Salts:** May antagonize the cardiac effects of magnesium.
* **Tetracyclines/Bisphosphonates:** Oral magnesium can decrease absorption; separate administration by at least 2-4 hours.
## Monitoring
* Serum magnesium levels (essential, especially with IV infusions and in renal impairment).
* Renal function (BUN, creatinine).
* Deep tendon reflexes.
* Respiratory rate and depth.
* Blood pressure.
* Cardiac rhythm (ECG).
## Clinical Pearls
* Magnesium sulfate is available as injectable and oral formulations. Oral absorption is variable.
* When administering IV, it should be infused slowly to avoid hypotension and other adverse effects.
* Carry an emergency cart with calcium gluconate available for reversal of severe magnesium toxicity.
* For IV infusion, it's often diluted in solutions like D5W or normal saline. Check compatibility.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and local institutional protocols before making any treatment decisions.*
