Phenobarbitone

Pathology category

Biochemistry - referred tests

Code

PHEB

Referral code

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Test information

Phenobarbitone is an antiepileptic drug Results on samples taken before steady-state has been achieved (1 – 2 weeks in children; 2 – 4 weeks in adults) will be unhelpful, except to confirm a diagnosis of toxicity If valproate is added to phenobarbitone regime, plasma phenobarbitone levels increase sharply in the majority of patients, and a reduction in dose is usually required

Guidelines

Pre-analytical

The long half life of phenobarbitone means that timing of samples in relationship to dosage is generally unimportant.

Reference range

15-40 mg/L

Tube type

Tube type info

SST or Plain

Special requirements

Serum

Minimum volume

500 uL

Assay frequency

TAT Inpatient (urgent)

TAT Inpatient

2 weeks

TAT GP/Outpatient

2 weeks

Referral lab

Regional Toxicology Laboratory, City Hospital