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HelpTest Code LAB4160 PHENOBARBITAL LEVEL
Additional Codes
Labcorp 007823
Specimen Type
Preferred Sample: Lithium Heparin Plasma (Mint Green Top, Dark Green Top)
Alternative Sample: Serum (SST, Gold, Corvac, Tiger, Red Top Tube) EDTA Plasma (lavender Top)
Specimen Volume
1 mL
Minimum Volume
0.5 mL
Turnaround Time
STAT: 1 hour
Routine: 4 hours
Test Schedule
Daily
Sample Stability
Room Temp: 7 days
Refrigerated: 6 months
Frozen: 6 months
Method
Colorimetric
Reference Ranges
Phenobarbital µg/mL
Therapeutic: 15.0-40.0
Toxic: Greater than 50.0
Reporting Limit
2.0 - 131.3 ug/mL
Synonyms
Luminal
CPT Codes
80184
Test Components
Phenobarbital, µg/mL.
Collection Instructions
Draw just prior to next dose. Note times of dose and drawing.
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 wtihin 24 hours of collection.
Clinical Information
Phenobarbital was introduced in 1912 for the treatment of epilepsy, particularly for controlling focal motor or sensory seizures and grand mal seizures. Phenobarbital is bound to both plasma and tissue proteins. Monitoring serum concentrations of phenobarbital has been shown to improve patient therapy by providing physicians with a tool for adjusting dosage. In addition, because of the narrow therapeutic index and wide inter-individual variability in the rate of phenobarbital metabolism and clearance, the determination of blood levels of phenobarbital for patients receiving therapy is important.