"Phenytoin is a selective serotonin reuptake inhibitor (SSRI) commonly used for epilepsy."

"The therapeutic range of phenytoin is 10-20 mcg/mL, and levels above this range can lead to toxicity."

"Phenytoin is contraindicated in clients with Parkinson's disease due to potential exacerbation of symptoms."

"Phenytoin is primarily metabolized by the liver and has no significant drug interactions."