The nurse is preparing to administer penicillin V potassium to a child with pneumonia. The child weighs 18.5 kg. The prescription is 50 mg/kg/day PO divided doses every six hours. How many milligrams should the child receive with each dose? Round to the nearest whole number.

• A. 200 mg
• B. 231 mg
• C. 235 mg
• D. 240 mg

Answer: (B)

The main idea is to convert the prescribed mg/kg per day into an amount given per dose, using the dosing interval. First determine the total daily dose: multiply the child’s weight by the mg prescribed per kg per day. 18.5 kg × 50 mg/kg/day = 925 mg per day. Since the antibiotic is given every six hours, that’s four doses per day (24 hours ÷ 6 hours = 4). Divide the total daily dose by the number of doses: 925 mg ÷ 4 = 231.25 mg per dose. Round to the nearest whole number, yielding 231 mg per dose.