Phenytoin toxicity presenting with acute visual loss and acute delirium, a case report

Phenytoin is a widely prescribed antiepileptic agent for both focal and generalized seizure. We report a case of a 20-year-old man with focal epilepsy presented with acute bilateral visual loss, and delirium. His random phenytoin serum concentration on admission was 43.6 mg/L, well above the recommended therapeutic range of 10-20 mg/L. Extensive investigations have ruled out other vascular or demyelinating causes. His visual symptoms completely resolved after discontinuing phenytoin for 84 hours. This case shows that acute phenytoin toxicity can result in reversible visual failure.