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Test Code DILA Phenytoin (Dilantin)

Specimen and Container/Tube

Specimen Type: Serum

Preferred Specimen: Red Top

Other Acceptable specimens: N/A

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be sent room temperature at 20-25oC.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours.

Reference Values

Test

Age

Sex

Reference Range

Dilantin

All

All

10 - 20 μg/mL

Critical Values

Analyte

Unit

Low

High

Age

Dilantin

μg/mL

N/A

>40

All

CPT Codes

80185

LOINC Codes

3968-5

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL

Specimen Stability

Storage Temperature

Stability

Room temperature

4 days

Refrigerated

4 days

Frozen

2 months

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

Test Components

Phenytoin (Dilantin)

Clinical Indications

Serum level monitoring of the drug is essential in order to achieve maximal seizure control while maintaining minimal blood levels.

Methodology

Kinetic Interaction of Microparticles in solution (KIMS), Roche Diagnostics

Additional Information

  • Results should always be assessed in conjunction with patient's medical history, clinical examination and other findings.
  • Usual sampling time varies dependent upon desired measurement of peak or trough values.
  • Due to the observed cross-reactivity of this assay to fosphenytoin, it is recommended that samples for serum phenytoin measurements be collected at least 2 hours after an intravernous dose of fosphenytoin and at least 4 hours after an intramuscular dose.
  • Because of individual variation in absorption and metabolism of the drug, optimum levels may vary and reach higher than 20 μg/mL or they may fall below 10 μg/mL.

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: 1 hour

Routine Turnaround Time: 4 hours

Testing Schedule: 24/7

Synonyms/Keyword Search

Diphenylhydantoin, D.P.H., Dilantin, Phenytoin, PNYA, PHNY2

Last Review Date

1/26/23