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HelpTest Code PHNB Phenobarbital
Specimen Requirements
Submit only one of the following:
Preferred
Specimen Type: Serum
Container/Tube: Gold Top (SSTII)
Volume: 5.0 mL
Minimum Volume: 0.5 mL serum
Collection Instructions: Allow specimen to clot for 30 mins and centrifuge within 2 hrs.
Acceptable
Specimen Type: Plasma
Container/Tube: Green Top (Li Heparin/PST)
Volume: 4.5 mL
Minimum Volume: 0.5 mL plasma
Collection Instructions: Centrifuge within 2 hrs.
Specimen Stability
| Specimen Type | Serum/Plasma |
|---|---|
| Ambient | 7 days |
| Refrigerate | 6 months |
| Frozen | 6 months |
Specimen Condition
| Haemolysis | OK |
|---|---|
| Icterus | OK |
| Lipaemia | OK |
| Others | Not applicable |
Methodology
Particle-Enhanced Turbidimetric Inhibition Immunoassay (PETINIA)
Days and Times Performed
24 hrs, TAT 1 day
Reference Interval
The desired therapeutic effect is usually achieved in the serum concentration range of 15 to 40 mg/L. Concentrations of 35 to 80 mg/L are associated with slowness, ataxia, and nystagmus.
Concentrations of 65 to 117 mg/L are associated with coma with reflexes.
Concentrations > 100 mg/L are associated with coma without reflexes.
Critical value: > 40 mg/L
Testing Laboratory
National University Hospital
Clinical Chemistry, 67724346
Useful For
Therapeutic drug monitoring.
Service Code
31821
Update
Last updated 12/03/2025
Alias
Phenobarbitone
Laboratory Code
LAB30
LOINC Code Information
3948-7