Magnesium%2525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520sulphate

# Magnesium Sulphate ## Overview Magnesium sulphate is an essential mineral involved in numerous biochemical reactions, including neuromuscular transmission and muscle contraction. It is available in parenteral and oral formulations. ## Primary Indications * **Parenteral:** Treatment of hypomagnesemia, management of eclampsia and severe preeclampsia, treatment of torsades de pointes, management of status epilepticus refractory to other agents, bronchodilation in asthma exacerbations (adjunctive). * **Oral:** Treatment of hypomagnesemia, laxative effect. ## Adult Dosing * **Hypomagnesemia:** * **Severe (serum Mg < 1.5 mEq/L or 0.75 mmol/L):** 4-6 grams IV as an initial dose, followed by 2-4 grams IV every 4-12 hours as needed, guided by serum magnesium levels and clinical response. Maximum recommended dose typically 20-30 grams over 24 hours, but can be higher in critical care under close monitoring. * **Mild to Moderate:** Lower doses may be used, guided by serum magnesium. * **Eclampsia/Severe Preeclampsia:** Typically 4-6 grams IV loading dose over 5-10 minutes, followed by a continuous IV infusion of 1-2 grams per hour. Local protocols vary significantly. Some may use IM loading doses. * **Torsades de Pointes:** 1-2 grams IV (diluted in 10-100 mL D5W or NS) infused over 5-10 minutes. Further doses may be repeated every 5-15 minutes as needed, followed by an infusion of 1 gram per hour for at least 12-24 hours if the rhythm resolves. * **Status Epilepticus (refractory):** 2-4 grams IV infused over 10-20 minutes. * **Asthma (adjunctive):** 1-2 grams IV infused over 15-30 minutes. * **Laxative (Oral):** 15-30 mL of a 50% oral solution, or 2-6 grams of anhydrous magnesium sulphate dissolved in water. Onset is usually within 0.5-6 hours. ## Pediatric Dosing Dosing in pediatric patients is highly variable and should be guided by specific clinical indications, patient weight, and local institutional protocols. * **Hypomagnesemia:** Doses of 25-50 mg/kg IV have been used, often up to a maximum of 2 grams per dose. Repeated every 4-6 hours. * **Eclampsia:** Similar to adults, but doses adjusted for weight. Often 20-40 mg/kg IV bolus, followed by an infusion. * **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 grams) over 10-20 minutes. * **Asthma (adjunctive):** 25-40 mg/kg IV infused over 15-30 minutes (maximum 2 grams). ## Dose Adjustments * **Renal Impairment:** Magnesium is renally excreted. Caution is advised in patients with moderate to severe renal impairment. Doses may need to be reduced and serum magnesium closely monitored to prevent accumulation and toxicity. ## Contraindications * Hypermagnesemia. * Heart block (excluding torsades de pointes). * Myocardial infarction. * Hypersensitivity to magnesium sulphate. * Bowel obstruction (for oral administration). ## Adverse Effects Common: Flushing, sweating, hypotension, nausea, vomiting, diarrhea (oral), decreased reflexes, drowsiness. Serious: Respiratory depression, cardiac arrhythmias, heart block, hypermagnesemia (muscle weakness, absent deep tendon reflexes, ECG changes, somnolence, confusion, respiratory arrest, cardiac arrest). ## Key Drug Interactions * **Neuromuscular Blockers:** Magnesium sulphate can potentiate neuromuscular blockade, leading to increased muscle weakness and respiratory depression. * **Calcium Salts:** Parenteral magnesium sulphate may precipitate with calcium salts. Avoid co-administration in the same IV line. * **Tetracyclines and Quinolones:** Oral magnesium sulphate can decrease the absorption of these antibiotics. Separate administration by at least 2 hours. * **Bisphosphonates:** Oral magnesium sulphate can decrease absorption. Separate administration by at least 2 hours. * **Digoxin:** Hypermagnesemia can increase the risk of digoxin toxicity. ## Monitoring * **Serum Magnesium Levels:** Crucial for guiding parenteral dosing and monitoring for efficacy and toxicity, especially in patients with renal impairment or receiving prolonged therapy. * **Renal Function:** Monitor BUN and creatinine, especially prior to and during therapy. * **Deep Tendon Reflexes:** Assess for loss of reflexes, which is an early sign of hypermagnesemia. * **Respiratory Rate and Effort:** Monitor for signs of respiratory depression. * **Cardiac Rhythm:** ECG monitoring is recommended, particularly with IV administration or in patients with cardiac conditions. * **Blood Pressure:** Monitor for hypotension. ## Clinical Pearls * Parenteral magnesium sulphate solutions for injection are typically available as 50% (500 mg/mL) solutions. Always calculate the dose in grams (elemental magnesium) and ensure appropriate dilution for IV infusion. * Rapid IV infusion can cause hypotension and cardiac depression. Infuse as recommended. * In eclampsia, magnesium sulphate is the drug of choice for seizure prophylaxis and treatment. Other agents may be considered if seizures persist. * Oral magnesium sulphate is a potent osmotic laxative; use with caution in patients with impaired renal function due to risk of accumulation. *** *This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional guidelines for definitive drug management.*