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Test Code DIL Dilantin

Additional Codes

Epic: LAB31

Specimen Required

Specimen Type: Serum

Collection Container/Type

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 3.5 mL

Collection Instructions: 

  1. Centrifuge and separate cells after clot formation and within 1 hours of collection. 

Specimen Minimum Volume

0.5 mL

Specimen Stability

Room temperature: 2 days

Refrigerated: 8 days

Frozen: 5 months

Clinical Significance

Phenytoin (Dilantin) is one of the most widely prescribed anticonvulsants and is occasionally used as a myocardial antiarrhythmic.  In the treatment of epilepsy, phenytoin is indicated for grand mal epilepsy (major motor) and cortical focal seizures and temporal lobe epilepsy.

The main pathway (about 90%) for disposition of phenytoin is by excretion in the urine.  It is hydroxylated in the liver and eliminated.  The metabolic conversion to HPPH is a saturable process and in many cases small increments in dosage can cause a large increase in phenytoin plasma level.    Because of the narrow therapeutic index and the wide inter-individual variability in the rate of phenytoin metabolism and clearance, the determination of blood levels of phenytoin for patients receiving therapy is appropriate.

Reference Range

Theraputic range: 10.0 - 20.0 µg/mL

Rejection Due To

Unlabeled, mislabeled, wrong tube type, QNS, grossly hemolyzed.

Day(s) and Time(s) Performed


Report Available

Same day

Method Name

Chemiluminescent Microparticle Immunoassay (CMIA)