Final answer:
The safe daily dose of phenytoin for a 15-pound child, according to the PDR, is 150 mg, considering the recommended maximum daily dose is 10 mg/kg/day and the child's weight converts to approximately 6.82 kg.
Step-by-step explanation:
The safe daily dose of phenytoin for this child is 150 mg.
The physician has ordered phenytoin syrup 20 mg PO bid, which means the prescribed dose is 20 mg taken twice a day (bid stands for twice a day). Since the child weighs 15 pounds, we first convert the weight to kilograms using the conversion factor 1 kilogram = 2.2 pounds. Therefore, the child weighs approximately 6.82 kg (15 pounds / 2.2). The PDR's maximum daily dose recommendation is 10 mg/kg/day, which means the child's maximum allowed dose per day is 68.2 mg (6.82 kg x 10 mg).
However, since the physician prescribed dosage is given twice a day, we multiply the single dose by 2 to calculate the total daily dose: 20 mg x 2 = 40 mg. This prescribed total daily dose of 40 mg is within the safe range because it is less than the maximum daily dose of 68.2 mg.
c) 150 mg, because the other options exceed the PDR's maximum daily dose recommendation.