Therapeutic drug management for patients with renal failure or conditions that may alter albumin concentrations.
New York DOH Approval Status
Timing of specimen collection: Pre-dose (trough) draw - At steady state concentration.
Separate serum from cells within 2 hours of collection. Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 1 mL)
Citrated plasma. Serum separator tubes (SST). Tubes that contain liquid anticoagulant.
After separation from cells: Ambient: 4 days; Refrigerated: 4 days; Frozen: 1 month
Quantitative Enzyme Multiplied Immunoassay Technique
Effective May 16, 2016
|Toxic:||Greater than 2.5 µg/mL|
Free phenytoin may be important to monitor in patients with altered or unpredictable protein binding capacity because phenytoin is highly bound (greater than 90 percent) at therapeutic concentrations. Phenytoin is also subject to drug-drug interactions due to displacement of protein binding and extensive metabolism. Cross-reactivity with metabolites may account for differences in phenytoin concentrations among analytical methods.
|Component Test Code*||Component Chart Name||LOINC|
|2010493||Phenytoin - Free||3969-3|