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# Magnesium Sulphate
## Overview
Magnesium sulphate is an essential mineral that plays a role in numerous biochemical reactions. It is available in parenteral and oral formulations.
## Primary Indications
* Treatment of hypomagnesemia
* Management of torsades de pointes
* Prevention and treatment of seizures in preeclampsia and eclampsia
## Adult Dosing
* **Hypomagnesemia:**
* Severe: 4-6 grams IV initially, followed by 1-2 grams/hour IV infusion. Dose and rate adjusted based on serum magnesium levels and clinical response.
* Less Severe: 1 gram IV every 12 hours for 4 doses.
* **Torsades de Pointes:** 1-2 grams IV diluted in 10-20 mL D5W or NS over 5-10 minutes. May repeat dose every 5-15 minutes if needed. Continuous infusion of 1-2 grams/hour may follow.
* **Preeclampsia/Eclampsia:**
* Loading Dose: 4-6 grams IV (diluted) infused over 5-20 minutes.
* Maintenance Dose: 1-2 grams/hour IV infusion. Adjust based on seizure recurrence and toxicity. Specific protocols vary; consult local guidelines.
## Pediatric Dosing
* **Hypomagnesemia:** Dosing is highly variable and based on weight and severity. A typical initial dose is 25-50 mg/kg IV (maximum 2 grams) over 5 minutes. Further doses or continuous infusion guided by serum magnesium levels and clinical response. Consult specialized pediatric resources.
* **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 grams) as a bolus, followed by an infusion of 1-2 grams/hour. Consult specialized pediatric resources.
* **Eclampsia (adjunctive):** Similar to hypomagnesemia dosing, but specific protocols are critical. Consult specialized pediatric resources.
## Dose Adjustments
* **Renal Impairment:** Magnesium is renally excreted. Reduce dose and monitor serum magnesium levels closely in patients with renal impairment. Use with caution in severe renal failure.
## Contraindications
* Heart block (unless a temporary pacemaker is in place)
* Hypermagnesemia
* Myocardial infarction
* Shock
## Adverse Effects
Common: Flushing, sweating, nausea, vomiting, somnolence, decreased deep tendon reflexes, hypotension.
Serious: Respiratory depression, cardiac arrest, hypermagnesemia (especially with renal impairment), hyperthermia.
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** Potentiates neuromuscular blockade; may require increased doses of these agents.
* **Calcium Salts:** Can antagonize the cardiac effects of magnesium.
* **Tetracyclines and Bisphosphonates:** Parenteral magnesium can decrease the absorption of oral tetracyclines and bisphosphonates; separate administration by at least 2-3 hours.
## Monitoring
* Serum magnesium levels (baseline and as needed based on dose and clinical status)
* Deep tendon reflexes
* Respiratory rate
* Blood pressure
* Urine output
* Electrocardiogram (ECG) in cases of suspected toxicity or rapid IV administration
## Clinical Pearls
* Rapid IV infusion can cause hypotension and cardiac dysrhythmias.
* Magnesium toxicity is more likely in patients with impaired renal function.
* Monitor for signs of hypermagnesemia, particularly decreased deep tendon reflexes, somnolence, and respiratory depression.
* For eclampsia, adherence to specific hospital protocols is crucial.
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*Disclaimer: This information is intended for healthcare professionals. Always verify current prescribing information with the official drug product labeling and consult relevant clinical guidelines before making any treatment decisions.*
