Can Magnesium Sulfate Be Diluted in 5% Dextrose?
Yes, magnesium sulfate can and should be diluted in 5% dextrose for intravenous administration. This is explicitly approved and recommended in FDA labeling and multiple clinical guidelines.
FDA-Approved Dilution Guidelines
The FDA drug label explicitly states that magnesium sulfate can be added to 5% dextrose for IV infusion 1:
- For hypomagnesemia: 5 g (approximately 40 mEq) can be added to one liter of 5% Dextrose Injection, USP for slow IV infusion over a three-hour period 1
- For preeclampsia/eclampsia: 4 to 5 g in 250 mL of 5% Dextrose Injection, USP may be infused 1
- Concentration requirement: Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration 1
Clinical Evidence Supporting This Practice
Research has directly validated the safety of magnesium sulfate diluted in 5% dextrose:
- A randomized crossover study in 12 adults demonstrated that IV infusion of MgSO4 (4 g/100 mL) in 5% dextrose over 4 hours poses no significant deleterious effects on cardiovascular, liver, kidney, or metabolic function 2
- The only notable effect was an expected increase in serum glucose concentration, which is attributable to the dextrose carrier solution 2
Alternative Diluent Options
While 5% dextrose is appropriate, the FDA also approves 0.9% sodium chloride as an alternative diluent 1:
- Both 5% Dextrose Injection, USP and 0.9% Sodium Chloride Injection, USP are commonly used diluents 1
- The choice between dextrose and saline should be based on the clinical context (e.g., avoiding dextrose in hyperglycemic patients)
Important Administration Precautions
When using magnesium sulfate in 5% dextrose, monitor for:
- Rate of administration: Generally should not exceed 150 mg/minute (1.5 mL of a 10% concentration), except in severe eclampsia with seizures 1
- Serum magnesium levels: Should be monitored to avoid toxicity, keeping levels below 5.5 mEq/L 3
- Clinical monitoring: Deep tendon reflexes, respiratory rate, and urine output should be assessed 4
- Renal function: In severe renal insufficiency, maximum dosage is 20 grams/48 hours with frequent serum magnesium monitoring 1
Common Pitfall to Avoid
Do not use undiluted 50% magnesium sulfate solution for IV infusion—this concentration is only appropriate for deep IM injection in adults 1. Always dilute to 20% or less for IV administration to prevent vein irritation and ensure safe infusion rates 1.