What is the typical intravenous dose of 50% magnesium sulfate used for neonatal hypomagnesemia?

• A. 0.5 to 1 mL/kg over 60 minutes
• B. 0.05 to 0.1 mL/kg of 50% MgSO4 over 30-60 minutes
• C. 0.01 to 0.02 mL/kg over 10 minutes
• D. 1.0 to 2.0 mL/kg over 2 hours

Answer: (B)

Neonatal magnesium repletion uses a small, precise volume of a concentrated solution to raise magnesium safely. The appropriate regimen is a dose of 0.05 to 0.1 mL/kg of 50% MgSO4 given over 30–60 minutes. A 50% solution contains about 500 mg/mL, so this corresponds to roughly 25–50 mg/kg delivered during the infusion. This amount corrects the deficiency without risking rapid overshoot into hypermagnesemia, which can depress respiration and cardiac function in neonates. After the infusion, closely monitor for signs of elevated magnesium—such as reduced reflexes, slowed breathing, or changes in heart rate or blood pressure—and check serum magnesium to guide further dosing. The other options would deliver too much, too little, or too rapid a dose for safe repletion.