Magnesium%25252525252525252525252525252525252525252525252525252525252525252520sulphate

# Magnesium Sulphate ## Overview Magnesium sulphate is an electrolyte that is essential for normal muscle and nerve function, blood glucose control, and blood pressure regulation. It is available intravenously (IV) and intramuscularly (IM). ## Primary Indications * Hypomagnesemia * Eclampsia and severe pre-eclampsia * Torsades de pointes * Status asthmaticus (adjunctive therapy) * Constipation (oral formulations) ## Adult Dosing **Hypomagnesemia:** * **Acute severe deficiency:** IV infusion of 4-5 grams (32-40 mEq) over 5-15 minutes, followed by 1-2 grams (8-16 mEq) per hour as a continuous infusion. The total daily dose should not exceed 20 grams (160 mEq) in 24 hours. * **Mild to moderate deficiency:** IV infusion of 1 gram (8 mEq) per hour for up to 12 hours, or IM injection of 1 gram (8 mEq) every 6 hours for 4 doses. **Eclampsia/Severe Pre-eclampsia:** * Loading dose: IV infusion of 4-6 grams (32-48 mEq) over 5-20 minutes. * Maintenance dose: IV infusion of 1-2 grams (8-16 mEq) per hour. Local protocols for duration and maximum doses should be followed. **Torsades de Pointes:** * IV bolus of 1-2 grams (8-16 mEq) in 10-20 mL D5W over 5-10 minutes. May repeat every 5-15 minutes. Follow with a continuous infusion of 0.5-1 gram (4-8 mEq) per hour. **Status Asthmaticus (Adjunctive):** * IV infusion of 2 grams (16 mEq) diluted in 100 mL saline over 15-20 minutes. **Constipation (Oral):** * Dosing varies by product; follow specific product labeling. ## Pediatric Dosing Dosing in pediatric patients should be based on ideal body weight and is often guided by local protocols and expert consultation due to limited robust data. **Hypomagnesemia:** * Loading dose: IV infusion of 25-50 mg/kg (2-4 mEq/kg) over 5-15 minutes. Maximum single dose usually 2 grams. * Maintenance dose: IV infusion of 20-30 mg/kg/hour (1.6-2.4 mEq/kg/hour). Maximum daily dose usually 200 mg/kg (16 mEq/kg) or 5 grams, whichever is less. **Eclampsia (Neonatal withdrawal):** * Dosing is highly variable and depends on clinical presentation and response, often requires specialist management. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment, as magnesium is primarily excreted by the kidneys. However, caution is advised in severe renal impairment due to the risk of accumulation. ## Contraindications * Heart block * Hypermagnesemia * Hypocalcemia (can precipitate tetany) * Myocardial infarction with heart block * Shock ## Adverse Effects * Flushing, sweating, hypotension, nausea, vomiting (especially with rapid infusion) * Drowsiness, decreased deep tendon reflexes, respiratory depression, cardiac arrhythmias, cardiac arrest (with hypermagnesemia) * Diarrhea (with oral formulations) ## Key Drug Interactions * **Neuromuscular blocking agents:** Magnesium can potentiate neuromuscular blockade. * **Calcium:** Hypermagnesemia can impair calcium absorption. * **Tetracyclines and Quinolones:** Magnesium can decrease the absorption of these antibiotics when administered concurrently. Separate administration by at least 2-3 hours. ## Monitoring * Serum magnesium levels (especially with prolonged infusions or impaired renal function) * Renal function (BUN, creatinine) * Deep tendon reflexes (for signs of hypermagnesemia) * Respiratory rate and effort (for signs of respiratory depression) * Cardiac rhythm (especially in patients with cardiac conditions) * Blood pressure ## Clinical Pearls * Always dilute magnesium sulphate for IV administration. A common concentration for infusion is 1 gram per 100 mL of IV fluid. * Rapid IV infusion can cause hypotension and respiratory depression. Administer IV doses slowly as recommended. * Monitor for signs and symptoms of hypermagnesemia, particularly in patients with renal insufficiency. * Magnesium sulphate can be administered IM, but it is painful. Infiltration with lidocaine may be considered. * For hypomagnesemia, correct hypocalcemia and hypokalemia concurrently if present, as these can impair magnesium repletion. *** *This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.*