CPT® Code 80185

The CPT® Code 80185 refers to a laboratory test that measures the total level of phenytoin in the blood. Phenytoin, commonly known by its brand names such as Dilantin, Phenytek, or Phenytoin Prompt, is an anticonvulsant medication primarily used to manage and treat seizures. This medication functions by reducing electrical activity in the brain, which is crucial for preventing seizure episodes. The administration of phenytoin can occur either orally or through injection, depending on the patient's needs and the clinical scenario. Due to its narrow therapeutic range, it is essential to monitor both total and free phenytoin levels in patients receiving this medication. The total phenytoin level indicates the overall serum concentration of the drug, while the free phenytoin level measures the unbound portion of the drug that is biologically active. It is important to note that approximately 90 percent of phenytoin is bound to plasma proteins and is considered biologically inactive. However, this bound form can be affected by other medications that displace phenytoin from its protein binding sites, potentially leading to an increase in free phenytoin levels in the bloodstream. Regular monitoring of blood concentration levels is critical, particularly during routine follow-ups and in instances of breakthrough seizures, which may suggest that the therapeutic levels of phenytoin are insufficient. The blood sample for this test is collected through a venipuncture, which is a separately reportable procedure. Following collection, the serum is analyzed using immunoassay techniques to determine the phenytoin levels accurately.