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# Magnesium Sulfate ## Overview Magnesium sulfate is an essential mineral used to treat and prevent hypomagnesemia and is also indicated for the management of seizures in preeclampsia and eclampsia. ## Primary Indications * Treatment of hypomagnesemia. * Prevention of hypomagnesemia in specific patient populations (e.g., alcoholism, malabsorption). * Management of seizures in preeclampsia and eclampsia. * Management of torsades de pointes. * Bronchodilator in severe asthma exacerbations. ## Adult Dosing * **Hypomagnesemia:** * **Severe Deficiency (serum Mg < 1.0 mEq/L or 0.5 mmol/L):** 4 to 6 grams IV over 5 to 60 minutes, followed by 2 to 4 grams every 4 to 12 hours as needed. * **Mild Deficiency (serum Mg 1.0-1.5 mEq/L or 0.5-0.75 mmol/L):** 2 to 6 grams IV or IM daily, divided into doses. * **Maintenance:** 1 gram IV or IM every 6 to 12 hours, or 5 grams orally every 6 hours. * **Preeclampsia/Eclampsia:** 4 to 6 grams IV loading dose, followed by a maintenance infusion of 1 to 2 grams per hour. Dosing may vary based on local protocol. * **Torsades de Pointes:** 1 to 2 grams IV diluted in 10 mL of D5W administered over 5 to 10 minutes, followed by an infusion of 0.5 to 1 gram per hour. * **Asthma Exacerbation:** 1 to 2 grams IV diluted in 100 mL NS over 15 to 30 minutes. ## Pediatric Dosing * **Hypomagnesemia:** * **Neonates:** 25 to 50 mg/kg/dose IV every 12 to 24 hours. * **Infants and Children:** 25 to 50 mg/kg/dose IV, maximum single dose 2 grams. May be repeated every 4 to 12 hours. Consider oral administration if feasible. Dosing is highly individualized and should be guided by serum magnesium levels and clinical response. * **Preeclampsia/Eclampsia:** Not typically recommended for routine use. Pediatric eclampsia management can be complex and requires specialized care. * **Torsades de Pointes:** 25 to 100 mg/kg IV (maximum 2 grams), as a continuous infusion over 10 to 20 minutes. ## Dose Adjustments * **Renal Impairment:** Magnesium is renally excreted. Use with caution and reduce dose in patients with renal impairment. Monitor serum magnesium levels closely. ## Contraindications * Hypermagnesemia. * Heart block or myocardial damage. * Severe renal impairment. ## Adverse Effects * **Common:** Flushing, sweating, nausea, vomiting, hypotension, hyporeflexia, drowsiness. * **Serious:** Respiratory depression, cardiac arrest, hypermagnesemia (lethargy, decreased reflexes, muscle weakness, ECG changes, difficulty breathing, cardiac arrhythmias, cardiac arrest). ## Key Drug Interactions * **Nifedipine:** May cause profound hypotension and neuromuscular blockade. * **Neuromuscular Blocking Agents (e.g., succinylcholine, vecuronium):** May potentiate neuromuscular blockade. * **Tetracyclines and Quinolones:** Magnesium can decrease the absorption of these antibiotics. Administer at least 2 hours before or 4-6 hours after magnesium. ## Monitoring * **Serum Magnesium Levels:** Monitor regularly, especially in patients with renal impairment or those receiving prolonged infusions. Target levels vary based on indication. * **Renal Function:** Assess baseline and monitor for changes. * **Deep Tendon Reflexes:** Assess for hyporeflexia. * **Respiratory Rate and Depth:** Monitor for signs of respiratory depression. * **Blood Pressure:** Monitor for hypotension. * **ECG:** Monitor for cardiac arrhythmias, especially with higher doses or in patients with underlying cardiac conditions. ## Clinical Pearls * Intravenous administration should be slow and carefully monitored due to the risk of hypotension and respiratory depression. * Rapid IV administration can cause a sensation of heat and flushing. * Magnesium is a CNS depressant; concurrent use of other CNS depressants may potentiate effects. * IV calcium should be readily available as an antidote for severe hypermagnesemia. * Oral magnesium is often used for maintenance or treatment of mild hypomagnesemia but can cause diarrhea. *** *This information is intended for clinical use and does not replace professional medical advice. Always verify current prescribing information, including indications, contraindications, warnings, and precautions, before dispensing or administering any medication.*