SD, a 66 year old man, has been started on phenytoin Na for treatment of seizures he has been experiencing after he experienced a head injury last week. after starting, he has been feeling drowsy, confused, and unable to balance himself. upon examination of his eyes, nystagmus has been observed. in addition to phenytoin Na, SD also takes aspirin and omeprazole. these symptoms are most likely due to...
a. poor seizure control
b. aura associated with impending seizure
c. adverse effects of phenytoin
d. subdural hematoma