Fasting Required: No Specimen: Blood Results: 3-5 Business Days Description: Phenytoin is a drug that is used to treat some seizure disorders. These disorders affect the brain's ability to transmit electrical impulses and to regulate nerve activity. During a seizure, a patient may experience changes in consciousness, alterations in sight, smell, taste, and may experience uncontrolled muscular convulsions of one or more parts of the body. Phenytoin works by reducing the electrical conductance among brain cells, blocking excessive electrochemical activity occurring in the brain during a seizure. Methodology: Immunoassay Reference Range(s): 10.0-20.0 mg/L Clinical Significance: Phenytoin is an anticonvulsant hydantoin used for the treatment of generalized tonic-clonic (grand mal) and complex partial seizures. Phenytoin is also used for prophylaxis in neurosurgical procedures. Phenytoin levels are monitored to assure adequate therapeutic levels are achieved and to avoid toxicity. Alternative Name(s): Dilantin®, Hydantoin