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# Magnesium Sulphate ## Overview Magnesium sulphate is an essential mineral involved in numerous enzymatic and physiological processes. It is available for intravenous and intramuscular administration. ## Primary Indications * Treatment of hypomagnesemia. * Management of seizures in preeclampsia and eclampsia. * Management of status epilepticus refractory to other treatments. * Treatment of torsades de pointes. * Management of acute bronchospasm in asthma. ## Adult Dosing * **Hypomagnesemia:** * **Severe (<1 mg/dL):** 4 to 8 grams IV over 1 to 24 hours. Followed by maintenance infusions of 1 to 4 grams every 4 to 12 hours, adjusted based on serum magnesium levels. * **Less severe (1-1.5 mg/dL):** 1 to 4 grams IV or IM divided into 4 doses over 24 hours. Followed by maintenance infusions as above. * **Preeclampsia/Eclampsia:** 4 to 6 grams IV loading dose, followed by a continuous infusion of 1 to 2 grams per hour. Alternative IM regimen: 5 grams IM in each buttock as a loading dose, followed by 5 grams IM every 4 hours. Dosing adjusted based on clinical response and serum magnesium levels. Local protocol is crucial. * **Status Epilepticus:** 2 to 4 grams IV over 5 to 10 minutes. May repeat if needed. Often part of a multi-drug regimen. * **Torsades de Pointes:** 1 to 2 grams IV in 10 mL D5W over 5 to 10 minutes. May repeat if necessary. Followed by a continuous infusion of 0.5 to 1 gram per hour. * **Acute Bronchospasm (Adjunctive therapy):** 2 grams IV diluted in 100 mL saline over 15 to 30 minutes. ## Pediatric Dosing * **Hypomagnesemia:** Dosing varies significantly by age and weight. Typical initial IV doses range from 25 to 50 mg/kg per dose (maximum 2 grams), administered over 10 to 15 minutes. Maintenance infusions are also common. Exact dosing should follow specific pediatric guidelines or local protocol. * **Status Epilepticus:** 25 to 50 mg/kg IV (maximum 2 grams) over 5 to 10 minutes. * **Preeclampsia/Eclampsia:** Not typically used in pediatric patients. ## Dose Adjustments No dose adjustment is generally required for hepatic impairment. In renal impairment, doses should be reduced and serum magnesium levels closely monitored due to risk of accumulation. ## Contraindications * Hypermagnesemia. * Heart block. * Myocardial infarction. * Bowel obstruction. * Gastric stasis. ## Adverse Effects Common: Flushing, sweating, hypotension, nausea, vomiting, decreased deep tendon reflexes, respiratory depression. Serious: Cardiac arrhythmias, cardiac arrest, loss of deep tendon reflexes, extreme somnolence, respiratory paralysis, hyperthermia. ## Key Drug Interactions * **Neuromuscular blocking agents:** Potentiates neuromuscular blockade, increasing risk of prolonged paralysis and respiratory depression. * **Calcium channel blockers:** Additive hypotensive effects and potential for enhanced neuromuscular blockade. * **Digitalis glycosides:** Use with caution in patients receiving digitalis; hypermagnesemia can potentiate cardiac toxicity. * **Certain antibiotics (e.g., aminoglycosides, tetracyclines):** May potentiate neuromuscular blockade. ## Monitoring * **Serum magnesium levels:** Crucial for guiding dosing and assessing efficacy/toxicity. Target levels vary by indication (e.g., 4-7 mEq/L for eclampsia). * **Renal function (serum creatinine):** Essential for dose adjustments. * **Deep tendon reflexes:** Assess for loss of reflexes, an early sign of hypermagnesemia. * **Respiratory rate and function:** Monitor for respiratory depression. * **Blood pressure and heart rate:** Monitor for hypotension and arrhythmias. * **Urine output:** Monitor for adequate renal function. ## Clinical Pearls * Magnesium sulphate administration can cause transient flushing and warmth. * Rapid IV administration can lead to hypotension and cardiac depression. * Intravenous calcium (e.g., calcium gluconate) is the antidote for severe magnesium toxicity. * In preeclampsia, adequate urine output is necessary before administering magnesium sulphate. --- **Educational Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information, institutional protocols, and individual patient factors before making treatment decisions.