A nurse is preparing to administer promethazine 25 mg PO. Available is promethazine syrup 6.25 mg/5 mL. How many mL should the nurse administer? (Round the answer to the nearest whole number. Use a leading zero if it applies. Do not use a trailing zero.)

Desired dose = 25 mg. Available concentration = 6.25 mg / 5 mL. Calculate the volume to administer. Volume (mL) = Desired dose (mg) / (Available concentration (mg) / Available volume (mL)) = 25 mg / (6.25 mg / 5 mL) = 25 mg × (5 mL / 6.25 mg) = (25 × 5) / 6.25 mL = 125 / 6.25 mL = 20 mL.