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# Magnesium Sulphate
## Overview
Magnesium sulphate is an electrolyte supplement and anticonvulsant. It is available in injectable and oral formulations.
## Primary Indications
* Treatment of hypomagnesemia.
* Management of seizures in preeclampsia and eclampsia.
* Management of status epilepticus refractory to first-line agents.
* Management of torsades de pointes.
## Adult Dosing
* **Hypomagnesemia:**
* **Severe:** 4-5 g IV administered over 5-15 minutes, followed by 1-2 g/hour via continuous infusion.
* **Moderate:** 2-4 g IM or IV.
* **Oral:** 3000 mg (approximately 3 g) orally per day in divided doses.
* **Preeclampsia/Eclampsia:** 4-6 g IV loading dose over 5-10 minutes, followed by 1-2 g/hour infusion. Alternative: 5 g IM into each buttock (total 10 g) with 1 mL of 1% procaine or 2% lidocaine.
* **Torsades de Pointes:** 1-2 g IV diluted in 10-20 mL D5W or NS, administered over 10-20 minutes. May repeat. May follow with infusion of 0.5-1 g/hour.
* **Status Epilepticus (refractory):** 2-4 g IV over 10-20 minutes.
*Note: Specific dosing and infusion rates for hypomagnesemia and eclampsia can vary based on local protocols and patient response.*
## Pediatric Dosing
* **Hypomagnesemia:**
* **IV:** 20-50 mg/kg/dose (maximum 2 g) over 10-15 minutes, may repeat every 4 hours as needed.
* **IM:** 25-50 mg/kg/dose (maximum 2 g) every 4-6 hours.
* **Infusion:** 10-30 mg/kg/hour.
* **Eclampsia:** 30-40 mg/kg IV loading dose over 10-20 minutes, followed by 10-20 mg/kg/hour infusion (maximum 1 g/hour).
* **Torsades de Pointes:** 25-50 mg/kg IV (maximum 2 g) over 10-20 minutes.
*Note: Pediatric dosing often follows specific institutional guidelines and may be adjusted based on clinical presentation and magnesium levels.*
## Dose Adjustments
* **Renal Impairment:** Use with extreme caution. Reduced doses may be necessary. Monitor magnesium levels closely. In severe renal impairment, avoid administration if possible.
## Contraindications
* Hypermagnesemia.
* Heart block.
* Myocardial infarction.
* Hyperkalemia.
* Bowel obstruction.
* Rectal or anal fissures/ulcers (for oral administration).
## Adverse Effects
* **Common:** Flushing, sweating, nausea, vomiting, diarrhea (oral), hypotension, bradycardia, decreased reflexes, drowsiness, muscle weakness, respiratory depression.
* **Severe:** Cardiac arrest, pulmonary edema, central nervous system depression.
## Key Drug Interactions
* **Neuromuscular blocking agents:** May potentiate neuromuscular blockade.
* **Calcium channel blockers:** Increased risk of hypotension and bradycardia.
* **Antibiotics (e.g., tetracyclines, quinolones):** Magnesium can decrease absorption. Administer antibiotics at least 2 hours before or 4-6 hours after magnesium.
* **Bisphosphonates:** May decrease absorption of bisphosphonates. Separate administration by at least 2 hours.
## Monitoring
* Serum magnesium levels.
* Respiratory rate and depth.
* Blood pressure and heart rate.
* Deep tendon reflexes.
* Urine output.
* Renal function (creatinine, BUN).
## Clinical Pearls
* Magnesium sulphate is a CNS depressant and can cause significant hypotension and respiratory depression. Closely monitor vital signs and respiratory status, especially with IV administration.
* IV administration should be done slowly to prevent hypotension.
* Oral magnesium sulphate can cause significant gastrointestinal upset.
* Correct hypocalcemia and hypokalemia concurrently if present, as these can exacerbate magnesium deficiency.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and institutional protocols for definitive guidance on drug selection, dosing, and administration.
