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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

Reference Range

Theraputic range: 10.0 - 20.0 µg/mL

Rejection Due To

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

Report Available

Same day

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.

Method Name

Chemiluminescent Microparticle Immunoassay (CMIA)

Aliases

Phenytoin

Day(s) Performed

Daily