Magnesium%252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520sulphate

# Magnesium Sulphate ## Overview Magnesium sulphate is an electrolyte supplement and anticonvulsant. It is available for intravenous (IV) and intramuscular (IM) administration. ## Primary Indications * **Hypomagnesemia:** To correct low serum magnesium levels. * **Preeclampsia/Eclampsia:** To prevent or treat seizures in patients with severe preeclampsia or eclampsia. * **Torsades de Pointes:** To treat polymorphic ventricular tachycardia associated with a prolonged QT interval. * **Status Asthmaticus:** As an adjunctive therapy in severe, refractory asthma. ## Adult Dosing * **Hypomagnesemia:** * **Acute Replacement:** 4-6 grams IV over 1-2 hours, followed by 1-2 grams per hour as a continuous infusion. Dosing is highly dependent on serum magnesium levels and patient response. * **IM Dosing:** 1 gram IM every 4 hours for 4 doses. * **Preeclampsia/Eclampsia:** * **Loading Dose:** 4-6 grams IV infused over 5-10 minutes. * **Maintenance Infusion:** 1-2 grams per hour IV. * **IM Dosing (alternative):** 5 grams IM in each buttock initially, followed by 5 grams IM in alternating buttocks every 4 hours. * Maximum dose typically not to exceed 30-40 grams in 24 hours. * **Torsades de Pointes:** 1-2 grams IV in 10 mL of D5W infused over 5 minutes, followed by 0.5-1 gram per hour IV infusion as needed. May repeat bolus if necessary. * **Status Asthmaticus:** 2 grams IV infused over 15-20 minutes. *Exact dosing often depends on local hospital protocols and magnesium level monitoring.* ## Pediatric Dosing * **Hypomagnesemia:** * **IV Infusion:** 20-50 mg/kg/dose IV infused over 10 minutes to 1 hour. May repeat every 4-12 hours. * **Continuous IV Infusion:** 4-10 mg/kg/hour. * Dosing is highly dependent on serum magnesium levels. * **Eclampsia (Adjunctive):** Dosing regimens are variable and often guided by expert consensus or local protocols. Common approaches may involve a loading dose of 20-40 mg/kg (maximum 2 grams) followed by an infusion. * **Status Asthmaticus:** 25-50 mg/kg IV infused over 15-20 minutes (maximum 2 grams). *Pediatric dosing requires careful consideration of weight-based calculations and close monitoring.* ## Dose Adjustments * **Renal Impairment:** Magnesium is renally excreted. Dose reduction and careful monitoring of magnesium levels and renal function are necessary in patients with impaired kidney function. In severe renal impairment, magnesium sulphate is generally contraindicated. ## Contraindications * Myocardial damage. * Heart block. * Hypermagnesemia. * Severe renal impairment. * Addison's disease. ## Adverse Effects * **Common:** Flushing, warmth, sweating, hypotension, decreased deep tendon reflexes, nausea, vomiting. * **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, coma, hypermagnesemia (e.g., hypotension, bradycardia, ECG changes, loss of deep tendon reflexes, muscle weakness, respiratory paralysis, cardiac arrest). ## Key Drug Interactions * **Neuromuscular Blockers (e.g., succinylcholine, vecuronium):** Magnesium sulphate can potentiate neuromuscular blockade, leading to prolonged respiratory depression. * **Calcium Salts:** Can antagonize the cardiac effects of magnesium. * **Tetracyclines and Bisphosphonates:** Absorption may be decreased if administered concurrently with oral magnesium. Separate administration by at least 2-3 hours. * **Nifedipine:** Concurrent use has been associated with profound hypotension and muscle weakness. ## Monitoring * **Serum Magnesium Levels:** Crucial for guiding dosing, especially in hypomagnesemia and during prolonged infusions. Target levels vary by indication. * **Renal Function (SCr, BUN):** Essential for dose adjustments and assessing risk of accumulation. * **Respiratory Rate and Depth:** Monitor for signs of respiratory depression. * **Deep Tendon Reflexes:** Loss of reflexes is an early sign of hypermagnesemia. * **Blood Pressure:** Monitor for hypotension. * **Cardiac Monitoring (ECG):** Monitor for arrhythmias and ECG changes consistent with hypermagnesemia. * **Urine Output:** Assess renal function and fluid balance. ## Clinical Pearls * IV administration is generally preferred for rapid correction and for treatment of eclampsia and torsades de pointes. * IM injections can be painful; consider co-administration with lidocaine per local protocol. * Always use an infusion pump for IV magnesium sulphate. * Discontinue magnesium sulphate if signs of hypermagnesemia appear. * Antidote for hypermagnesemia is IV calcium (e.g., calcium gluconate). *** ***Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and relevant clinical guidelines for definitive dosing and management strategies.*