Magnesium Sulfate Infusion Rate for Hypomagnesemia Treatment
For treating hypomagnesemia, magnesium sulfate should be administered over 10-20 minutes for patients with hypomagnesemia with pulses present. 1
Infusion Rate Guidelines Based on Clinical Scenario
- For mild to moderate hypomagnesemia with stable vital signs, administer magnesium sulfate at a dose of 25-50 mg/kg (maximum: 2 g) over 10-20 minutes 1
- For severe hypomagnesemia with cardiac manifestations (e.g., torsades de pointes with pulses), administer over 10-20 minutes 1
- For pulseless torsades de pointes associated with hypomagnesemia, administer as a bolus 1
- For status asthmaticus associated with hypomagnesemia, administer over 15-30 minutes 1
Dosing Recommendations
- For mild magnesium deficiency: 1 g (equivalent to 8.12 mEq of magnesium) injected IM every six hours for four doses 2
- For severe hypomagnesemia: Up to 250 mg (approximately 2 mEq) per kg of body weight may be given IM within a four-hour period 2
- Alternatively, 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 2
- For cardiac arrhythmias associated with hypomagnesemia: IV magnesium 1-2 g bolus is recommended regardless of measured serum levels 3
Important Considerations and Monitoring
- Rapid infusion of magnesium sulfate may cause hypotension and bradycardia 1
- Have calcium chloride available to reverse potential magnesium toxicity 1
- Monitor for signs of magnesium toxicity including hypotension, drowsiness, and muscle weakness 3
- The target serum magnesium level should be within the normal range (1.8-2.2 mEq/L) 3
- Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration 2
Special Situations
- For patients with renal insufficiency, the maximum dosage of magnesium sulfate is 20 grams/48 hours with frequent monitoring of serum magnesium concentrations 2
- In patients with short bowel syndrome or malabsorption, higher doses of oral magnesium or parenteral supplementation may be required 3
Pitfalls to Avoid
- Do not exceed the rate of IV injection of 150 mg/minute (1.5 mL of a 10% concentration or its equivalent) except in severe eclampsia with seizures 2
- Do not exceed a total daily (24 hr) dose of 30 to 40 g in pre-eclampsia or eclampsia 2
- Avoid continuous maternal administration of magnesium sulfate injection in pregnancy beyond 5 to 7 days as it can cause fetal abnormalities 2
The 10-20 minute infusion time is the most appropriate for treating standard hypomagnesemia, while the 4-hour infusion would be more appropriate for maintenance therapy or for very large doses in severe cases.