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HelpTest Code PHNB Phenobarbital
Additional Codes
| Epic Ordering Code | LAB30 |
| NBS code | LBC09152 |
| Service code | 31821 |
Specimen Requirements
Submit only one of the following:
| Preferred: | Acceptable: |
| Yellow Top | Light Green Top |
Processing Requirements
Allow specimen to clot for 30 mins (Yellow Top) and centrifuge within 2 hours
Specimen type: Serum
Volume: 0.5mL
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.
Update
Last updated 26/07/2026
LOINC Code Information
3948-7
Alias
Phenobarbitone