Blood, ArterialBlood, CapillaryBlood, Central LineBlood, Venous
Specimen Types
Blood
Container
Red Top Tube
Collection Instructions
Container/Tube: Plain, red-top tube(s) Specimen: 2.5 mL of serum (1.0 mL min) Transport Temperature: Refrigerate Stability: 4 Days Room temperature, 7 Days Refrigerated 30 Days Frozen Rejection: Gel-barrier tube; hemolysis; lipemia
Collect as a trough just prior to next dose. For patients receiving fosphenytoin therapy, collect as peak (at least 2 hours after IV infusion or at least 4 hours after IM injection).
Specimen Volume
2.5 mL of serum (1.0 mL min)
Transport Instructions
Refrigerate
Specimen Stability
4 Days Room temperature, 7 Days Refrigerated 30 Days Frozen Rejection: Gel-barrier tube; hemolysis; lipemia
Collect as a trough just prior to next dose. For patients receiving fosphenytoin therapy, collect as peak (at least 2 hours after IV infusio
Methodology
Ultrafiltration • Immunoassay (IA)
Days Performed
TAT: 1-2 Days
Performing Laboratory
Quest Diagnostics Nichols Institute
CPT
80186
LOINC Code: 3969-3
PDM
5902380
Only Orderable at Locations:
Orderable Everywhere
Results
Component Name
Base Name
Common Name
External Name
PHENYTOIN, FREE
PHENYTOIN
PHENYTOIN, FREE
Phenytoin, Free
Result Interpretation
Therapeutic: 1.0-2.0 ug/mL
Phenytoin is used singly or in combination with other anticonvulsants to treat grand mal epilepsy. Monitoring the serum levels of antiepileptic drugs has increased the efficiency and safety of drug therapy in epilepsy. It facilitates individualization of dosage regimen, reveals irregular drug intake and identifies the responsible agent in intoxicated patients on multiple drug therapy. Free phenytoin is especially useful in patients with altered phenytoin binding to protein, e.g., uremia or individuals having abnormally low levels of albumin, such as nephrotic syndrome. Free phenytoin in serum correlates better with the various other free compartments of the body than does the total drug and is probably a better estimate of the "active drug level" at the receptor site and agrees more with the clinical response.
