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## Magnesium Sulphate
### Overview
Magnesium sulphate is an essential mineral that plays a critical role in numerous physiological processes, including neuromuscular function, cardiac rhythm, and enzyme activity. It is available in both intravenous (IV) and intramuscular (IM) formulations.
### Primary Indications
* **Eclampsia and Preeclampsia:** Prevention and treatment of seizures associated with severe preeclampsia and eclampsia.
* **Torsades de Pointes:** Treatment of polymorphic ventricular tachycardia (torsades de pointes).
* **Hypomagnesemia:** Treatment of documented magnesium deficiency.
* **Bronchodilator:** Adjunctive therapy for severe or refractory asthma exacerbations.
### Adult Dosing
* **Eclampsia/Preeclampsia:**
* **Loading Dose:** 4-6 grams IV infused over 5-20 minutes.
* **Maintenance Dose:** 1-2 grams per hour IV infusion. Alternatively, 5 grams IM into each buttock every 4 hours. Dosing may vary based on local protocols and response.
* **Torsades de Pointes:**
* **Acute Infusion:** 1-2 grams IV in 5% dextrose in water (D5W) or normal saline (NS) infused over 5-10 minutes.
* **Continuous Infusion:** 2-4 grams IV over 1 hour, followed by 0.5-1 gram per hour.
* **Hypomagnesemia:**
* Dosing is highly individualized based on serum magnesium levels and clinical status. A common initial approach for severe deficiency is 4-6 grams IV over 4-6 hours, followed by maintenance infusions. Specific protocols are often utilized.
* **Asthma Exacerbation:**
* 1-2 grams IV infused over 15-30 minutes.
### Pediatric Dosing
* **Eclampsia/Preeclampsia:** Dosing is less established in pediatrics. Refer to specific pediatric guidelines or local protocols.
* **Torsades de Pointes:** 25-50 mg/kg IV, not to exceed 2 grams per dose, infused over 10-20 minutes.
* **Hypomagnesemia:** Dosing is individualized and depends on serum magnesium levels.
* **Asthma Exacerbation:** 25-50 mg/kg IV infused over 15-30 minutes, maximum 2 grams.
### Dose Adjustments
No specific dose adjustments are typically required for hepatic impairment. In **renal impairment**, doses should be reduced and serum magnesium levels closely monitored, as magnesium is renally excreted.
### Contraindications
* **Hypermagnesemia:** Known elevated serum magnesium levels.
* **Heart Block:** Greater than first-degree heart block without a pacemaker.
* **Myocardial Infarction:** Caution in patients with recent myocardial infarction.
* **Myasthenia Gravis:** Use with caution.
### Adverse Effects
* **Common:** Flushing, sweating, nausea, vomiting, decreased deep tendon reflexes, hypotension.
* **Serious:** Respiratory depression, cardiac arrhythmias, cardiac arrest, hypermagnesemia, coma.
### Key Drug Interactions
* **Neuromuscular Blockers:** Magnesium can potentiate the effects of nondepolarizing and depolarizing neuromuscular blocking agents.
* **Calcium Channel Blockers:** Increased risk of hypotension and bradycardia.
* **Nifedipine:** Concurrent use for tocolysis has been associated with maternal hypotension and hypocalcemia.
### Monitoring
* **Serum Magnesium Levels:** Regularly monitor, especially during prolonged infusions or in patients with renal impairment.
* **Deep Tendon Reflexes:** Assess for presence and symmetry. Loss of reflexes indicates toxicity.
* **Respiratory Rate:** Monitor for signs of respiratory depression.
* **Blood Pressure:** Monitor for hypotension.
* **Urine Output:** Monitor for adequate renal function.
* **Cardiac Rhythm:** Especially in patients receiving magnesium for torsades de pointes.
### Clinical Pearls
* Magnesium sulphate is a potent medication; careful dose calculation and administration are crucial.
* Always have calcium gluconate readily available as an antidote for magnesium toxicity.
* IV administration should be done via a slow infusion to minimize adverse effects.
* Hypomagnesemia can potentiate hypokalemia and hypocalcemia; monitor and correct these electrolytes as needed.
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*Disclaimer: This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always verify current prescribing information and consult with a qualified healthcare provider before making any treatment decisions.*
