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Test Code LAB4161 PHENYTOIN LEVEL, TOTAL

Specimen Type

Preferred Specimen: Lithium Heparin Plasma (PST, Mint Green Top, Dark Green)
Alternative Specimen:   Serum Tube (SST, Gold, Corvac, Tiger, Red Top Tube)

Collection Instructions

Draw just prior to next oral dose or 2-4 hours after IV loading dose. Note times of dose and drawing.

Specimen Volume

1 mL

Minimum Volume

0.5 mL

Turnaround Time

STAT: 1 hour
Routine: 4 hours

Test Schedule

Daily

Sample Stability

Room Temp: 2 days
Refrigerated: 1 month
Frozen: 5 months

Method

Colorimetric

Reference Ranges

Phenytoin                                 µg/mL

Therapeutic                             10.0-20.0

Toxic                                        Greater Than 25.0

Reporting Limit

0.8 - 80.0 ug/mL

Synonyms

Dilantin

Test Components

Phenytoin, µg/mL.

CPT Codes

80185

Test Limitations

Studies have shown that therapeutic drug levels may be altered in serum/plasma that remains in contact with separator gel. Therapeutic drug levels collected in an SST or PST should be run within 24 hrs of collection.