Magnesium Sulfate Dilution Guidelines
Magnesium sulfate for intravenous administration should be diluted to a concentration of 20% or less prior to administration, typically in 5% Dextrose Injection or 0.9% Sodium Chloride Injection. 1
Dilution Guidelines by Clinical Indication
For Magnesium Deficiency:
- For severe hypomagnesemia, 5 g (approximately 40 mEq) can be added to one liter of 5% Dextrose Injection or 0.9% Sodium Chloride Injection for slow IV infusion over a three-hour period 1
For Pre-eclampsia or Eclampsia:
- Initial dose: 4 to 5 g in 250 mL of 5% Dextrose Injection or 0.9% Sodium Chloride Injection 1
- Alternative method: Dilute the 50% solution to a 10% or 20% concentration (40 mL of a 10% solution or 20 mL of a 20% solution) for IV injection over 3-4 minutes 1
- For maintenance infusion: 1-2 g/hour by constant IV infusion 1
For Anaphylaxis:
- Standard concentration: Add 4 mg of norepinephrine to 250 mL of D5W to yield a concentration of 16 μg/mL 2
- Alternative concentration: Add 1 mg (1 mL) of a 1:1000 dilution of epinephrine to 250 mL of D5W to yield a concentration of 4.0 μg/mL 3
- For severe reactions requiring IV epinephrine: 1:100,000 solution (1 mg in 100 mL of saline) administered at an initial rate of 30 to 100 mL/h 3
Administration Considerations
Rate of Administration:
- The rate of IV injection should generally not exceed 150 mg/minute (1.5 mL of a 10% concentration or its equivalent) 1
- For pre-eclampsia/eclampsia, administer the diluted solution over 3-4 minutes 1
Fluid Volume Considerations:
- For patients requiring fluid resuscitation, 1-2 L of normal saline should be administered at a rate of 5-10 mL/kg in the first 5 minutes 3, 4
- Patients with congestive heart failure or chronic renal disease should be monitored closely to prevent volume overload 3, 4
- For children, administer up to 30 mL/kg in the first hour 3, 4
Monitoring During Administration
- Monitor serum magnesium levels; 6 mg/100 mL is considered optimal for seizure control 3
- In severe renal insufficiency, maximum dosage should not exceed 20 grams/48 hours with frequent monitoring of serum magnesium concentrations 1
- Total daily dose should not exceed 30-40 g in a 24-hour period 1
- Continuous maternal administration beyond 5-7 days can cause fetal abnormalities 1
Special Considerations
- Deep IM injection of the undiluted (50%) solution is appropriate for adults, but should be diluted to 20% or less for children 1
- For patients receiving colloid solutions, administer 500 mL rapidly, followed by slow infusion 3
- Be aware that increased vascular permeability in anaphylaxis might permit transfer of 50% of intravascular fluid into extravascular space within 10 minutes 3
Remember that proper dilution is critical for safe administration of magnesium sulfate, and the concentration should never exceed 20% for intravenous administration 1.