Hello You asked the side effects of EPTOIN i.e. phenytoin , these are: Hypersensitivity ,lack of appetite, headache , dizziness , tremor, transient nervousness, insomnia, nausea, vomiting, constipation, tenderness & hyperplasia of gums, acne, hirsutism,coarsening of the facial features ,rashes, osteomalacia. Eptoin toxicity manifested as syndrome of cerebellar , vestibular & ocular effects, notably nystagmus , diplopia, , slurred speech, & ataxia also with mental confusion, dyskinesias , exacerbation of seizures & hyperglycemia. These are side effects of eptoin if drug is taken orally. Now answer for 2nd question. Yes, this drug can be given to a serious brain damage patient depending on the symptoms of patient and requirement . Hope this will will help you. Good luck.