Please check your internet connection and try again.
# Magnesium Sulphate
## Overview
Magnesium sulfate is an inorganic salt essential for various enzymatic and physiological functions. It is available for intravenous (IV) and intramuscular (IM) administration.
## Primary Indications
* Hypomagnesemia
* Torsades de Pointes (with or without QT prolongation)
* Eclampsia and Preeclampsia prophylaxis and treatment
* Bronchodilator adjunct in acute severe asthma (limited evidence)
## Adult Dosing
Dosing is highly dependent on indication and patient magnesium levels.
* **Hypomagnesemia:**
* **Severe:** IV: 4-6 grams infused over 1-4 hours, followed by a continuous infusion of 1-3 grams per hour. Maximum infusion rate generally not to exceed 1 gram/hour.
* **Moderate:** IM: 1 gram every 4-6 hours for up to 4 doses.
* **Maintenance:** IV: 4-6 grams daily, divided into doses.
* **Torsades de Pointes:** IV: 1-2 grams in 10-50 mL D5W over 5-10 minutes. May repeat doses every 5-15 minutes. Continuous infusion of 0.5-1 gram/hour may be used after initial bolus.
* **Eclampsia/Preeclampsia:** Protocol-driven. A common regimen (Browne's regimen or similar):
* **Loading Dose:** IV: 4-6 grams infused over 5-10 minutes.
* **Maintenance Dose:** IV: 1-2 grams per hour via continuous infusion.
* IM: 5 grams in each buttock for a total of 10 grams, followed by 5 grams in alternating buttocks every 4 hours.
* **Asthma:** IV: 40 mg/kg (maximum 2 grams) as a single dose infused over 15-30 minutes.
## Pediatric Dosing
Dosing is highly dependent on indication and patient magnesium levels.
* **Hypomagnesemia:**
* **Severe:** IV: 25-50 mg/kg per dose infused over 1-4 hours. May be followed by an infusion of 10-20 mg/kg/hour.
* **Moderate:** IM: 20-50 mg/kg per dose every 4-6 hours for up to 4 doses.
* **Torsades de Pointes:** IV: 25-50 mg/kg as a single dose infused over 10-20 minutes. May repeat. Continuous infusion may be used.
* **Eclampsia/Preeclampsia:** Refer to obstetric protocols; dosing may vary significantly.
* **Asthma:** Limited data. IV: 25-50 mg/kg (maximum 2 grams) infused over 15-30 minutes.
## Dose Adjustments
Renal impairment: Dose reduction and careful monitoring are necessary. Magnesium is renally excreted; avoid in severe renal failure unless essential and with close monitoring.
## Contraindications
* Hypermagnesemia
* Heart block
* Myocardial infarction with hemodynamic instability
* Severe renal impairment
## Adverse Effects
* **Common:** Flushing, sweating, nausea, vomiting, hyporeflexia, hypotension.
* **Serious:** Respiratory depression, cardiac arrest, hypermagnesemia (somnolence, confusion, decreased reflexes, hypotension, bradycardia, cardiac arrhythmias).
## Key Drug Interactions
* **Neuromuscular Blocking Agents:** Magnesium can potentiate neuromuscular blockade, leading to prolonged respiratory depression.
* **Calcium:** Calcium administration may antagonize the effects of magnesium sulfate.
* **Tetracyclines and Quinolones:** Magnesium can reduce the absorption of these antibiotics; administer them at least 2 hours before or 4-6 hours after magnesium.
## Monitoring
* **Serum Magnesium Levels:** Baseline and regularly during therapy, especially with infusions. Therapeutic goal typically 1.7-3.5 mEq/L (for hypomagnesemia, higher levels may be targeted for eclampsia).
* **Renal Function (BUN, Creatinine):** Essential due to renal excretion.
* **Deep Tendon Reflexes:** Loss of reflexes indicates toxicity.
* **Respiratory Rate and Effort:** Monitor for respiratory depression.
* **Blood Pressure and Heart Rate:** Monitor for hypotension and bradyarrhythmias.
* **Urine Output:** Adequate renal function is crucial.
## Clinical Pearls
* IV magnesium sulfate can cause flushing and a sensation of heat.
* Rapid IV infusion can cause hypotension and cardiac depression.
* Loss of deep tendon reflexes is an early sign of magnesium toxicity.
* Always have calcium gluconate readily available as an antidote for magnesium toxicity.
* Dosing for eclampsia/preeclampsia is highly protocolized and may vary by institution.
***
*This information is intended for healthcare professionals. Always consult the most current prescribing information, institutional protocols, and other relevant resources before making clinical decisions. Drug information can change rapidly.*
