| Test Name: |
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Phenobarbital
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| Test Code(s): |
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PENO / PHEN
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| CPT Code(s): |
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80184
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| Methodology: |
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Particle Enhanced Turbidometric Inhibition Immunoassay (PETINIA)
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| Clinical Significance: |
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Anticonvulsant, sedative
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| Days Performed: |
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Daily, 24 hours.
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| Turnaround Time: |
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Stat: 1 hour.
Routine: 4 hours.
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Specimen Requirements
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| Specimen: |
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Blood
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| Collection Instructions: |
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Collect specimen within 30 minutes prior to the morning dose.
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| Collection Container: |
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Preferred: Red top
Also Acceptable:
Green top (with lithium heparin anticoagulant)
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| Collection Volume: |
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Preferred: 2 mL
Pediatrics: 0.4 mL
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| Sample Analyzed: |
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Serum or plasma
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| Volume Required: |
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Preferred: 1 mL
Pediatrics: 0.2 mL
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| Specimen Processing: |
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Centrifuge. Transfer cell-free serum or plasma to plastic vial. Refrigerate.
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| Specimen Transport: |
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Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.
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| Unacceptable Criteria: |
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Specimens collected in red cap with yellow ring (SST) or green cap with yellow ring (PST)tubes are not acceptable.
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| Stability: |
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Refrigerated: 7 days
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Interpretation
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Generally effective therapeutic concentration: 15-40 mcg/mL
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| Critical Calls: |
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View
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| Additional Information: |
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Result of "BELOW" indicates that the level is below the instrument detection limit of 2.1 mcg/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.
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