A nurse is preparing to administer cephalexin 50 mg/kg/day in divided doses every 8 hours to a child who weighs 33 lb. The amount available is cephalexin oral suspension 250 mg/5 mL. How many mL should the nurse administer per dose?

Step 1 is to convert the child’s weight to kilograms. 33 lb ÷ (2.2 lb/kg) = 15 kg. Step 2 is to calculate the total daily dose. 50 mg × 15 kg = 750 mg/day. Step 3 is to divide the total daily dose into three doses, as it is given every 8 hours. 750 mg ÷ 3 = 250 mg per dose. Step 4 is to calculate the volume per dose. (250 mg ÷ 250 mg/5 mL) = 5 mL. The nurse should administer 5 mL per dose.