Phenytoin treatment may be aşociated with adverse effects including nystagmus, dysarthria, ataxia, choreoathetosis, orofacial dyskinesia, seizure induction, lethargy, stupor-coma, and rarely acute psychotic attacks with delusion. A 36-year-old male patient who had undergone surgery for a carotid aneurysm three months before and had been on phenytoin treatment (300 mg/day) presented with visual hallucinations, hostile thoughts, aggreşive behaviors, delusions of persecution and jealousy, homicidal thoughts, dysarthria, nystagmus, hypotonia, and incoordination. The blood level of phenytoin was measured as 68 mg/ml. Phenytoin was ceased during clinical follow-up and antipsychotic therapy was given for three days. All clinical manifestations subsided and finally improved within two weeks. Phenytoin intoxication should be considered in the etiology of short-term psychiatric disorders especially in patients at risk.

Keywords: Abnormalities, drug-induced/etiology;brain/drug effects, drug tolerance, mental disorders/chemically induced, phenytoin/blood/adverse effects