A patient weighs 180 pounds and has a dopamine prescription of 5 mcg/kg/min. The dopamine comes in a bag labeled 200 mg in 250 mL of D5W. Approximately how many mL per hour will deliver the prescribed dose?

• A. 25 mL/hr
• B. 31 mL/hr
• C. 40 mL/hr
• D. 50 mL/hr

Answer: (B)

The main idea here is converting a weight-based dose into an infusion rate using the drug’s concentration. First, convert the patient’s weight to kilograms since the dose is given per kilogram: 180 lb ÷ 2.2046 ≈ 81.65 kg.

Multiply by the prescribed rate to get the dose per minute: 5 mcg/kg/min × 81.65 kg ≈ 408 mcg/min, which is 0.408 mg/min.

Next, use the solution’s concentration to turn that dose into a volume per minute. The syringe contains 200 mg in 250 mL, which is 200 mg ÷ 250 mL = 0.8 mg/mL. To deliver 0.408 mg/min, the infusion rate is 0.408 mg/min ÷ 0.8 mg/mL ≈ 0.51 mL/min.

Finally, convert to per hour: 0.51 mL/min × 60 min/hr ≈ 30.6 mL/hr, which rounds to about 31 mL/hr.

So the infusion should run at roughly 31 mL per hour. If you rounded earlier steps differently, you might land on nearby values like 25, 40, or 50 mL/hr, but carefully carrying all conversions leads to about 31 mL/hr.