If a physician orders 500 mg of drug to be infused in 1000 mL over 8 hours, what is the infusion rate in mL/hr?

If a physician orders 500 mg of drug to be infused in 1000 mL over 8 hours, what is the infusion rate in mL/hr?

• A. 140 mL/hr
• B. 100 mL/hr
• C. 1250 mL/hr
• D. 125 mL/hr

Answer: (D)

The key idea is that the infusion rate is the total volume to be infused divided by the total time. Here, you need to deliver 1000 mL over 8 hours, so 1000 mL ÷ 8 h = 125 mL per hour. The 500 mg dose doesn’t affect the rate calculation unless you’re asked for mg per hour or mg per mL; with the information given, only the volume and time matter. A rate of 125 mL/h will deliver the full 1000 mL in 8 hours, while the other rates would end up delivering a different total volume in that same time. So the correct infusion rate is 125 mL/hr.

The key idea is that the infusion rate is the total volume to be infused divided by the total time. Here, you need to deliver 1000 mL over 8 hours, so 1000 mL ÷ 8 h = 125 mL per hour. The 500 mg dose doesn’t affect the rate calculation unless you’re asked for mg per hour or mg per mL; with the information given, only the volume and time matter. A rate of 125 mL/h will deliver the full 1000 mL in 8 hours, while the other rates would end up delivering a different total volume in that same time. So the correct infusion rate is 125 mL/hr.