What is the correct setting for a burette pump to administer 40 mL of fluid containing 600 mg of penicillin in 20 minutes?

What is the correct setting for a burette pump to administer 40 mL of fluid containing 600 mg of penicillin in 20 minutes?

• A. 100 mL/h
• B. 140 mL/h
• C. 125 mL/h
• D. 120 mL/h

Answer: (D)

The key idea is to translate the required delivery time into a per-hour rate. You want to give 40 mL in 20 minutes. That’s 2 mL every minute (40 ÷ 20). Convert minutes to hours: 20 minutes is 1/3 hour, so 2 mL per minute is 2 × 60 = 120 mL per hour. Setting the burette pump to 120 mL/h will deliver exactly 40 mL in 20 minutes. The solution contains 600 mg in 40 mL, which is 15 mg/mL. Delivering 40 mL in 20 minutes provides the full 600 mg in that time, assuming concentration stays constant. If you used a different rate, you’d finish the 40 mL in a different amount of time, or you’d deliver more or less than 40 mL in 20 minutes, which would miss the planned dose timing. For example, a rate of 100 mL/h would take 24 minutes to deliver 40 mL, and a rate of 140 mL/h would deliver the same 40 mL in less than 20 minutes, effectively delivering a different timing.

The key idea is to translate the required delivery time into a per-hour rate. You want to give 40 mL in 20 minutes. That’s 2 mL every minute (40 ÷ 20). Convert minutes to hours: 20 minutes is 1/3 hour, so 2 mL per minute is 2 × 60 = 120 mL per hour. Setting the burette pump to 120 mL/h will deliver exactly 40 mL in 20 minutes.

The solution contains 600 mg in 40 mL, which is 15 mg/mL. Delivering 40 mL in 20 minutes provides the full 600 mg in that time, assuming concentration stays constant. If you used a different rate, you’d finish the 40 mL in a different amount of time, or you’d deliver more or less than 40 mL in 20 minutes, which would miss the planned dose timing. For example, a rate of 100 mL/h would take 24 minutes to deliver 40 mL, and a rate of 140 mL/h would deliver the same 40 mL in less than 20 minutes, effectively delivering a different timing.