Neurologists may prescribe C. dilantin for grand mal epilepsy.
This drug is generally used to treat or stop seizures, and since epilepsy is a type of a seizure, this should be recommended by neurologists.
Thorazine is an antipsychotic medication; lithium is used to treat bipolar disorder; prozac is an antidepressant - so these three drugs are used to treat mental disorders, whereas only B treats seizures.