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HelpTest ID VALPF Valproic Acid, Free, Serum
Useful For
Monitoring free valproic acid in therapy
Assessing compliance
Evaluating potential toxicity
Method Name
Ultrafiltration Followed by Immunoassay
Reporting Name
Valproic Acid, Free, SSpecimen Type
SerumContainer/Tube:
Preferred: Serum gel
Acceptable: Red top
Specimen Volume: 2
mL
Collection
Instructions:
1. Serum gel tubes should be centrifuged within 2 hours of
collection.
2. Red-top tubes should be centrifuged and aliquoted within 2 hours
of collection.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 14 days |
| Frozen | 28 days | |
| Ambient | 72 hours |
Clinical Information
Valproate (valproate, Depakote, or Depakene) is an effective medication for absence seizures, generalized tonic-clonic seizures, and partial seizures, when administered alone or in conjunction with other antiepileptic agents.
The valproic acid that circulates in blood is 85% to90% protein-bound under normal circumstances. In uremia or during concomitant therapy with other drugs that are highly protein-bound (such as phenytoin), valproic acid is displaced from protein, resulting in a higher free fraction of the drug circulating in blood.
Since neurologic activity and toxicity of valproic acid are directly related to the unbound fraction of drug, adjustment of dosage based on knowledge of the free valproic acid concentration may be useful in the following situations: concomitant use of highly protein-bound drugs (usually >80% bound), hypoalbuminemia, pregnancy, renal or hepatic failure, and in the elderly. In these situations, the total valproic acid concentration in the blood may underestimate the disproportionately higher free valproic acid fraction.
Reference Values
Therapeutic: 5-25 mcg/mL
Critical value: >30 mcg/mL
Cautions
Specimens subjected to significant heat or other factors that could cause protein denaturation would demonstrate an artificially increased free valproic acid.
Day(s) Performed
Monday through Sunday; Continuously
Report Available
Same day/1dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
80165