Based on a dose of 4.5 mg/kg for ATG and a patient weighing 60 kg, what infusion rate in mL/hour should be programmed if the vial is 25 mg per 10 mL and the total dose is delivered over 6 hours?

• A. 9 mL/hour
• B. 18 mL/hour
• C. 27 mL/hour
• D. 36 mL/hour

Answer: (B)

Start by converting the weight-based dose to a total milligram dose. 4.5 mg/kg × 60 kg = 270 mg total.

Next, use the vial’s concentration to find how much volume contains 270 mg. The preparation is 25 mg in 10 mL, which is 2.5 mg per mL. So the required volume is 270 mg ÷ 2.5 mg/mL = 108 mL.

Finally, divide that volume by the infusion time to get the rate: 108 mL ÷ 6 hours = 18 mL/hour.

So, program the infusion at 18 mL/hour. Rates like 9 mL/hour would deliver too little volume in 6 hours, while 27 or 36 mL/hour would deliver more volume than prescribed in the same time.