Feb 8, 2018




Clinical Hub,Tools & Resources,UWHC Lab Test Directory,Toxicology


Phenobarbital (PHEN) Toxicology Lab Test

Name: Phenobarbital

Test Name: Phenobarbital

Health Link Test Code: PHEN

LIS Test Code: PENO

CPT Code(s): 80184

Methodology: Particle Enhanced Turbidometric Inhibition Immunoassay (PETINIA)

Clinical Information:

Anticonvulsant, sedative

Days Performed: Daily, 24 hours.

In-Lab Turnaround Time: 4 hours.

Stat In-Lab Turnaround Time: 1 hour.

Specimen: Blood

Collection Container: Red top

Also Acceptable: Green top (with lithium heparin anticoagulant)

Collection Instructions:

Collect specimen within 30 minutes prior to the morning dose.

Collection Volume: 2 mL

Pediatric Collection Volume: 0.4 mL

Stability Ambient:

7 days

Stability Refridgerated:

6 months

Stability Frozen:

6 months

Sample Analyzed: Serum or plasma

Testing Volume: 1 mL

Pediatric Testing Volume: 0.2 mL

Specimen Processing:

Centrifuge. Transfer cell-free serum or plasma to plastic vial. Refrigerate.

Specimen Transport:

Transport specimen to the laboratory. Transport with coolant pack if coming from clinic location.

Unacceptable Criteria:

Specimens collected in red cap with yellow ring (SST) or green cap with yellow ring (PST)tubes are not acceptable.


Generally effective therapeutic concentration: 15.0-40.0 ug/mL

Critical Calls: yes

Additional Information:

Result of "BELOW" indicates that the level is below the instrument detection limit of 2.0 ug/mL. The half-life is approximately 4 days. The average peak blood concentration following oral administration is approximately 4.5 hours. Concurrent administration with valproic acid may cause a marked increase in the phenobarbital concentration. It may require 14-21 days to achieve steady state. Phenobarbital is considered an hepatic enzyme inducer. It is not extensively protein bound and is both hepatically and renally eliminated.