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# Magnesium Sulphate
## Overview
Magnesium sulfate is an electrolyte that plays a crucial role in various cellular functions. It is administered parenterally for specific medical conditions.
## Primary Indications
* Treatment of severe preeclampsia and eclampsia.
* Management of torsades de pointes.
* Correction of hypomagnesemia.
* Adjunct in status asthmaticus.
## Adult Dosing
* **Preeclampsia/Eclampsia:** Loading dose: 4-6 grams IV infused over 5-20 minutes. Maintenance dose: 1-2 grams per hour by continuous IV infusion. Dosing may vary based on local protocols and patient response.
* **Torsades de Pointes:** 1-2 grams IV in 10 mL D5W infused rapidly over 5-10 minutes. May repeat every 5-15 minutes. Further doses may be given as continuous infusion (e.g., 2-4 grams over 1 hour).
* **Hypomagnesemia:**
* **Severe symptomatic:** 2-4 grams IV infused over 10-30 minutes.
* **Less severe:** 1 gram/hour by continuous IV infusion.
* Dosing is weight-based in some contexts (e.g., 20-50 mg/kg/dose).
* **Status Asthmaticus:** 2 grams diluted in 50-100 mL normal saline infused over 15-30 minutes.
## Pediatric Dosing
* **Preeclampsia/Eclampsia:** Dosing is often based on adult protocols and may require specialist consultation. Typical maintenance may be 1 gram/hour percutaneous infusion.
* **Torsades de Pointes:** 25-50 mg/kg IV infused over 10-20 minutes. Maximum single dose 2 grams.
* **Hypomagnesemia:** 20-50 mg/kg/dose IV infused over 10-30 minutes. Maximum dose 2 grams. May be followed by continuous infusion of 0.5-1 g/kg/day.
* **Status Asthmaticus:** 25-50 mg/kg IV infused over 15-30 minutes. Maximum dose 2 grams.
## Dose Adjustments
* Dose reduction is necessary in patients with impaired renal function. Specific adjustments depend on the degree of renal impairment and serum magnesium levels.
## Contraindications
* Hypermagnesemia.
* Heart block (unless a temporary pacemaker is in place).
* Myocardial infarction.
* Malignant hyperthermia.
* Hypocalcemia (relative contraindication; may worsen hypocalcemia).
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, nausea, vomiting, decreased deep tendon reflexes, somnolence, respiratory depression.
* **Serious:** Cardiac arrest, respiratory paralysis, hypermagnesemia (symptoms include absent reflexes, hypotension, bradycardia, confusion, cardiac arrhythmias).
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** May potentiate neuromuscular blockade, leading to prolonged respiratory depression.
* **Calcium Salts:** Can antagonize the cardiac and CNS depressant effects of magnesium.
* **Nifedipine:** Concomitant use in preeclampsia may increase the risk of hypotension and decreased deep tendon reflexes.
* **Digitalis Glycosides:** Magnesium can potentiate digitalis toxicity, particularly in the presence of hypokalemia and hypomagnesemia.
## Monitoring
* **Essential:** Serum magnesium levels, blood pressure, respiratory rate, deep tendon reflexes, urine output.
* **Consider:** ECG, serum calcium, serum potassium.
## Clinical Pearls
* Magnesium sulfate can cause flushing and a feeling of warmth.
* Monitor for signs of hypermagnesemia, especially with rapid infusion or in renal impairment.
* Calcium gluconate (10% solution) should be readily available as an antidote for severe magnesium toxicity.
* In preeclampsia, continuous infusion is preferred for maintenance therapy.
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*This information is for educational purposes only and does not substitute for professional medical advice. Always verify the current prescribing information and consult with a healthcare provider for any health concerns or before making any decisions related to your health or treatment.*
