Magnesium sulfate is ordered at 2 g/hour. The label shows 20 g in 500 mL of 0.9% saline. How many milliliters per hour should be infused?

Magnesium sulfate is ordered at 2 g/hour. The label shows 20 g in 500 mL of 0.9% saline. How many milliliters per hour should be infused?

• A. 25 mL/hr
• B. 50 mL/hr
• C. 100 mL/hr
• D. 5 mL/hr

Answer: (B)

The calculation tests IV infusion rate by converting the prescribed dose into a volume using the solution’s concentration. The label provides 20 g in 500 mL, which is 20/500 = 0.04 g/mL (40 mg/mL). To deliver 2 g per hour, divide by the concentration: 2 g/hour ÷ 0.04 g/mL = 50 mL/hour. So, infuse at 50 mL per hour.

The calculation tests IV infusion rate by converting the prescribed dose into a volume using the solution’s concentration. The label provides 20 g in 500 mL, which is 20/500 = 0.04 g/mL (40 mg/mL). To deliver 2 g per hour, divide by the concentration: 2 g/hour ÷ 0.04 g/mL = 50 mL/hour. So, infuse at 50 mL per hour.