Magnesium%2525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520sulphate

# Magnesium Sulphate ## Overview Magnesium sulfate is an inorganic salt that acts as an electrolyte and has neuromuscular and central nervous system depressant effects. ## Primary Indications * Treatment of hypomagnesemia. * Prevention and treatment of seizures in preeclampsia and eclampsia. * Management of torsades de pointes. * Treatment of status asthmaticus (adjunctive). * Treatment of severe bronchospasm (adjunctive). ## Adult Dosing * **Hypomagnesemia:** * Severe deficiency: 4-5 grams IV initially, followed by 1-2 grams IV every 4-6 hours for a total of 24 hours or until deep tendon reflexes return and respiratory rate is adequate. May be followed by oral magnesium if needed. * Less severe deficiency: 1 gram IV or IM every 6 hours for 4 doses. * Continuous infusion: 1-2 grams/hour IV may be considered for severe or refractory hypomagnesemia. * **Preeclampsia/Eclampsia Prophylaxis:** 4-5 grams IV in 250 mL of dextrose 5% in water (D5W) or 0.9% sodium chloride over 15-30 minutes, followed by a maintenance infusion of 1-2 grams/hour. * **Preeclampsia/Eclampsia Treatment (Seizures):** 4-5 grams IV in 250 mL D5W or 0.9% NaCl over 15-30 minutes. If seizures persist or recur, administer a secondary bolus of 2.5 grams IV over 5 minutes. Follow with a maintenance infusion of 1-2 grams/hour. Alternative IM loading dose: 5 grams IM (deep gluteal) in each buttock, followed by 5 grams IM every 4 hours. * **Torsades de Pointes:** 1-2 grams IV in 10-20 mL D5W or 0.9% NaCl administered over 5-10 minutes. May repeat every 5-15 minutes. Further doses may be given as an infusion of 0.5-1 gram/hour. * **Status Asthmaticus/Severe Bronchospasm:** 1-2 grams IV diluted in 50-100 mL of 0.9% NaCl administered over 15-30 minutes. Maximum dose and infusion rates are typically guided by institutional protocols and patient response. ## Pediatric Dosing Dosing is highly variable and depends on indication, severity, and patient weight. Consultation with a pediatric specialist or reference is recommended. * **Hypomagnesemia:** Typically 25-50 mg/kg/dose IV or IM every 4-6 hours. Maximum single dose usually 1-2 grams. * **Preeclampsia/Eclampsia Prophylaxis/Treatment:** Similar dosing to adults may be used in adolescents, but requires careful calculation based on weight and institutional guidelines. * **Status Asthmaticus/Severe Bronchospasm:** 25-50 mg/kg IV over 10-20 minutes. Maximum dose typically 2 grams. ## Dose Adjustments * **Renal Impairment:** Magnesium is renally excreted. In patients with impaired renal function, doses should be reduced and serum magnesium levels monitored closely to avoid accumulation and toxicity. Use with caution in moderate to severe renal impairment. ## Contraindications * Hypermagnesemia. * Heart block. * Myocardial infarction (caution). * Anuria (caution). ## Adverse Effects Common: Flushing, sweating, hypotension, nausea, vomiting, decreased deep tendon reflexes, respiratory depression. Serious: Cardiac arrhythmias, cardiac arrest, CNS depression, neuromuscular blockade, hypermagnesemia. ## Key Drug Interactions * **Nifedipine:** Increased risk of hypotension and neuromuscular blockade. * **Neuromuscular Blockers (e.g., succinylcholine, vecuronium):** Potentiates neuromuscular blockade, increasing the risk of prolonged apnea and muscle weakness. * **Aminoglycosides:** May enhance neuromuscular blockade. * **Calcium Salts:** May antagonize the effects of magnesium. ## Monitoring * **Serum Magnesium Levels:** Monitor frequently, especially during IV infusions and in patients with renal impairment. Therapeutic range for hypomagnesemia treatment is typically 4-7 mEq/L (2-3.5 mmol/L), but may vary. Target levels for eclampsia are usually 4-8 mEq/L (2-4 mmol/L). * **Renal Function:** Monitor BUN and creatinine. * **Deep Tendon Reflexes:** Assess before and during administration. Loss of reflexes indicates toxicity. * **Respiratory Rate and Effort:** Monitor closely for signs of respiratory depression. * **Blood Pressure:** Monitor for hypotension. * **Urine Output:** Maintain adequate urine output (e.g., >100 mL/4 hours) to aid magnesium excretion. ## Clinical Pearls * Magnesium sulfate can be administered intravenously (IV), intramuscularly (IM), or orally. IV is preferred for acute, severe conditions. IM injections are painful and should be given deep into the gluteal muscle. Oral magnesium is often used for chronic repletion but has a laxative effect. * Always dilute magnesium sulfate before IV administration. * Have calcium gluconate readily available as an antidote for magnesium toxicity. * Discontinue magnesium sulfate if deep tendon reflexes are lost, respiratory rate falls below 16 breaths/minute, or urine output is inadequate. * In preeclampsia/eclampsia, the goal is seizure prevention/treatment, not correction of magnesium levels per se. Dosing is based on established protocols. *** **Disclaimer:** This information is intended for healthcare professionals. Always consult the official prescribing information and current clinical guidelines for complete details and to confirm dosage and safety before prescribing or administering any medication.