Phenobarbitone, serum
Clinical Background:
Phenobarbital (5 ethyl 5 phenylbarbituric acid) is the most effective barbiturate in long term treatment of seizure disorders. It is indicated for control in most types of seizures. Strong correlat...
Phenobarbital (5 ethyl 5 phenylbarbituric acid) is the most effective barbiturate in long term treatment of seizure disorders. It is indicated for control in most types of seizures. Strong correlation has been observed between serum levels and both therapeutic and toxic effects.
In most instances, effective seizure control is observed with serum levels between 15 mg/L and 40 mg/L. Toxic effects are often associated with serum levels above 40 mg/L.
Phenobarbital is excreted, partly metabolised (main metabolite: ~hydroxy phenobarbital) and partly unchanged, very slowly through the urine. Both metabolism and clearance are highly variable among individuals; therefore, close monitoring of serum levels is essential for every patient undergoing phenobarbital therapy.
The half-life of Phenobarbitone in adults is approximately 100 hours so it takes up to 3 weeks to reach steady state concentrations. The half life of the parent compound Primidone is 10 hours and is more rapidly absorbed so peak levels are seen after only 3 hours.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Adult:
Serum (SST or plain tube)
Serum (SST or plain tube)
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Specimen Container Paediatric:
Serum (SST or plain tube)
Serum (SST or plain tube)
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Minimum Volume Adult:
1 mL blood
1 mL blood
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Minimum Volume Paediatric:
0.5 mL blood
0.5 mL blood
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Special Requirement:
Ideally trough sample should be taken but if not possible then sample taken at same time for monitoring
Ideally trough sample should be taken but if not possible then sample taken at same time for monitoring
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Sample Stability:
Unseparated sample: 2 days
Separated sample: 7 days at 15-25°C, 7 days at 2-8°C, 1 year at -20°CUnseparated sample: 2 days
Separated sample: 7 days at 15-25°C, 7 days at 2-8°C, 1 year at -20°C -
Reference Ranges:
Therapeutic Range: 10 - 40 mg/L
Therapeutic Range: 10 - 40 mg/L
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Other Info:
Plasma- Lithium Heparin also acceptable
Plasma- Lithium Heparin also acceptable
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Routine Contact Name:
Duty Biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719Freeman: 0191 244 8889
RVI: 0191 282 9719 -
Routine Email: