The Client Has Epilepsy and Receives Phenytoin (Dilantin)

The client has epilepsy and receives phenytoin (Dilantin) . The client has been seizure -free, and asks the nurse why he still needs blood tests when he is not having seizures. What is the best response by the nurse?

A) "Because phenytoin (Dilantin) can cause blood -thinning in some clients."
B) "Because phenytoin (Dilantin) can cause Stevens -Johnson syndrome, which will show up in the blood tests."
C) "Because phenytoin (Dilantin) has a very narrow range between a therapeutic dose and a toxic dose."
D) "Because phenytoin (Dilantin) can deplete your system of potassium."