A child weighing 25 kg is prescribed methylprednisolone 0.5 mg/kg/day to be given IM in divided doses every 12 hours. The medication is in a 20 mg/mL vial. How many mL should be given with each dose?

• A. 0.1
• B. 0.3
• C. 0.6
• D. 1.0

Answer: (B)

This question tests converting a weight-based dose to a volume using the drug’s concentration. Start with the patient’s weight: 25 kg and the ordered dose is 0.5 mg/kg/day, so total daily dose = 25 × 0.5 = 12.5 mg. Since the dose is divided into two injections per day, each dose = 12.5 ÷ 2 = 6.25 mg. The vial provides 20 mg per mL, so the volume for each dose = 6.25 mg ÷ 20 mg/mL = 0.3125 mL, which rounds to 0.3 mL per dose.