A child with a seizure disorder receives a prescription for phenytoin 20 mg by mouth every 8 hours. The suspension is available in 125 mg/5 mL. How many ml. should the nurse administer? (Enter the numerical value only. If rounding is required, round to the nearest tenth.)

To determine how many ml of phenytoin suspension the nurse should administer, we need to find out how many mg of phenytoin are in one ml of suspension. To do this, we need to divide the concentration of phenytoin in mg by the volume of suspension in mL. Therefore, the amount of phenytoin in one ml of suspension is 125 / 5 = 25 mg/mL. Next, we need to divide the prescribed dose of phenytoin in mg by this amount to get the volume of suspension in mL that contains that dose. The result is 20 / 25 = 0.8 mL.