Intravenous Magnesium Sulfate Infusion Rates
For intravenous magnesium sulfate administration, the recommended infusion rate is 1-2 grams over 15-20 minutes for most acute conditions, with specific rates varying by indication. 1
General Administration Guidelines
The infusion rate for IV magnesium sulfate depends on the clinical indication:
Acute Conditions
- Polymorphic VT/Torsades de pointes: 1-2 g IV over 15 minutes 2
- Hypomagnesemia with pulses: 1-2 g over 10-20 minutes 2
- Status asthmaticus: 1-2 g over 15-30 minutes 2, 1
Obstetric Indications
- Pre-eclampsia/Eclampsia:
- Loading dose: 4-5 g IV over 3-4 minutes (diluted to 10-20% solution)
- Maintenance: 1-2 g/hour by continuous IV infusion 3
Pediatric Dosing
Important Safety Considerations
Monitoring Requirements
- Continuous monitoring of vital signs (blood pressure, heart rate, respiratory rate)
- Monitor deep tendon reflexes (loss of patellar reflex occurs at 3.5-5 mmol/L)
- Monitor oxygen saturation
- Have calcium salts available to counteract potential magnesium toxicity 1
Precautions
- Rapid infusion risks: Hypotension, bradycardia, respiratory depression, and cardiac arrest 1
- Renal insufficiency: Maximum dosage should not exceed 20 g/48 hours with frequent serum magnesium monitoring 2, 1, 3
- Total daily dose: Should not exceed 30-40 g in 24 hours 3
Solution Preparation
- Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration
- Common diluents: 5% Dextrose Injection or 0.9% Sodium Chloride Injection 3
Clinical Pearls
- Therapeutic serum magnesium levels for treatment of eclamptic convulsions range from 1.8 to 3.0 mmol/L 4
- Body mass index may affect serum magnesium levels, with higher BMI patients potentially requiring higher infusion rates to achieve therapeutic levels 5
- Magnesium sulfate may cause significant blood pressure reduction, especially in hypertensive pregnant patients 6
- For patients with renal dysfunction, dose adjustments are necessary based on serum creatinine levels 7
Warning Signs of Toxicity
- Loss of patellar reflex: First warning sign (3.5-5 mmol/L)
- Respiratory depression: Occurs at 5-6.5 mmol/L
- Cardiac conduction alterations: >7.5 mmol/L
- Cardiac arrest: >12.5 mmol/L 4
Remember that the infusion rate should be carefully controlled, ideally using an infusion pump, and patients should be closely monitored throughout administration for signs of magnesium toxicity.