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# Magnesium Sulphate
## Overview
Magnesium sulphate is an electrolyte that plays a crucial role in numerous biochemical reactions. It is available for intravenous (IV) and intramuscular (IM) administration.
## Primary Indications
* Treatment of hypomagnesemia.
* Prevention and treatment of seizures in preeclampsia and eclampsia.
* Management of torsades de pointes.
* Management of severe asthma exacerbations (adjunctive therapy).
* Treatment of status epilepticus (adjunctive therapy).
## Adult Dosing
* **Hypomagnesemia:**
* Severe deficiency: 4-6 grams (approximately 32-48 mEq) IV infused over 10-15 minutes, followed by 2 grams (16 mEq) per hour via continuous infusion for up to 24 hours.
* Less severe deficiency: 1-2 grams (8-16 mEq) IV or IM every 6 hours as needed.
* **Preeclampsia/Eclampsia:**
* Loading dose: 4-6 grams IV infused over 15-20 minutes.
* Maintenance dose: 1-2 grams per hour via continuous IV infusion.
* Alternative IM regimen: 5 grams IM in each buttock initially, followed by 5 grams IM every 4 hours.
* **Torsades de Pointes:** 1-2 grams (8-16 mEq) IV in 10-20 mL of D5W or NS over 5-10 minutes. Additional doses may be given if needed.
* **Severe Asthma/Status Epilepticus (Adjunctive):** 1-2 grams IV infused over 15-20 minutes.
Dosing often depends on specific clinical protocols and patient response.
## Pediatric Dosing
Dosing in pediatric patients is highly variable and depends on the indication, patient weight, and severity of the condition. Consult pediatric-specific guidelines.
* **Hypomagnesemia:** 25-50 mg/kg/dose IV infused over 10-15 minutes, not to exceed 2 grams. Further doses may be administered to a maximum of 100 mg/kg/day.
* **Preeclampsia/Eclampsia (adjunctive):** Refer to adult protocols or specialized pediatric guidelines.
* **Torsades de Pointes:** 25-50 mg/kg IV over 10-20 minutes, not to exceed 2 grams.
## Dose Adjustments
No specific dose adjustment is typically required for renal impairment, but caution is advised. In severe renal impairment, accumulation can occur. Magnesium sulphate is removed by hemodialysis. Monitor serum magnesium levels closely.
## Contraindications
* Hypermagnesemia.
* Heart block or myocardial damage.
## Adverse Effects
* **Common:** Flushing, sweating, hypotension, decreased deep tendon reflexes, nausea, vomiting.
* **Serious:** Respiratory depression, cardiac arrest, hypermagnesemia (especially in renal impairment).
## Key Drug Interactions
* **Neuromuscular Blockers:** Magnesium can potentiate neuromuscular blockade, leading to prolonged muscle weakness or respiratory depression.
* **Calcium:** Concurrent administration can antagonize the effects of magnesium.
* **Tetracyclines and Quinolones:** Magnesium can decrease the absorption of these antibiotics; separate administration by at least 2 hours.
## Monitoring
* **Vital signs:** Blood pressure, heart rate, respiratory rate.
* **Neurological status:** Deep tendon reflexes, level of consciousness.
* **Renal function:** Serum creatinine.
* **Serum magnesium levels:** Especially in patients with renal impairment or those receiving prolonged infusions. Therapeutic levels for eclampsia are typically 4-7 mEq/L.
## Clinical Pearls
* IV infusions should be administered slowly to avoid hypotension and flushing.
* Assess deep tendon reflexes before each dose; if absent, withhold the dose.
* Have calcium gluconate readily available as an antidote for magnesium toxicity.
* For IM administration, divide the dose between two large muscle masses to reduce pain and risk of sciatic nerve irritation.
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**Disclaimer:** This information is intended for healthcare professionals. Always verify current prescribing information and consult with a qualified healthcare provider before making any treatment decisions.
