Magnesium Sulfate IV Administration Guidelines
For management of magnesium levels with IV magnesium sulfate, administer 1-2 g IV over 15 minutes for acute hypomagnesemia, followed by maintenance infusion of 1 g/hour for 24 hours if needed. 1, 2
Dosing by Clinical Indication
Hypomagnesemia
- For mild magnesium deficiency: 1 g IV (equivalent to 8.12 mEq) every 6 hours for 4 doses 2
- For severe hypomagnesemia: Up to 250 mg/kg IV over 4 hours, or 5 g added to 1 liter of IV fluid for slow infusion over 3 hours 2
- Maintenance therapy should be titrated based on serum magnesium levels, with target range of 1.3-2.2 mEq/L 1
Cardiac Arrhythmias
- For polymorphic VT associated with QT prolongation (torsades de pointes): 1-2 g IV over 15 minutes 1
- For persistent torsades: May repeat 2 g doses as needed 3
Pre-eclampsia/Eclampsia
- Loading dose: 4-6 g IV over 20-30 minutes 4
- Maintenance: 1-2 g/hour continuous infusion for 24 hours 4, 2
- Alternative regimen: 4-5 g IV in 250 mL of compatible IV fluid, with simultaneous IM doses up to 10 g (5 g in each buttock) 2
- Total daily dose should not exceed 30-40 g in 24 hours 2
- Lower maintenance dose (1 g/hour) has similar efficacy to 2 g/hour with fewer side effects 5
Severe Asthma
- For severe refractory asthma: 2 g IV diluted to 20% or less concentration, administered over 20 minutes 4, 3
- Not recommended for mild to moderate asthma exacerbations 3
Administration Guidelines
Preparation
- Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration 2
- Common diluents: 5% Dextrose Injection or 0.9% Sodium Chloride Injection 2
Administration Rate
- Standard IV injection rate should not exceed 150 mg/minute (1.5 mL of a 10% solution) 2
- Exception: Severe eclampsia with seizures may require faster administration 2
Monitoring
- Monitor deep tendon reflexes (loss of patellar reflex occurs at 3.5-5 mmol/L) 6
- Monitor respiratory rate (respiratory depression occurs at 5-6.5 mmol/L) 6
- Monitor urine output (oliguria is a common side effect) 5
- Monitor serum magnesium levels (therapeutic range: 1.8-3.0 mmol/L for eclampsia treatment) 6
- Have calcium immediately available to counteract magnesium toxicity 4
Precautions
- Use with caution in patients with renal insufficiency; maximum dose should be 20 g/48 hours with frequent monitoring of serum magnesium 2
- Continuous use in pregnancy beyond 5-7 days can cause fetal abnormalities 2
- Common side effects include flushing, hypotension, and bradycardia 1, 5
- Cardiac conduction abnormalities occur at levels >7.5 mmol/L, and cardiac arrest can occur at >12.5 mmol/L 6
Special Considerations
- QRS interval length may increase during infusion but is generally not clinically significant at therapeutic doses 7
- Discontinue administration as soon as desired effect is obtained 2
This evidence-based approach to magnesium sulfate administration provides clear guidance for dosing and monitoring while prioritizing patient safety and efficacy across various clinical indications.