VALPROIC ACID, FREE

Code
900.5470
Name
VALPROIC ACID, FREE
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
Depakene, Depakote, Unbound Valproic Acid
CPT Codes
80164
Site
SBMF
Reference Test
29075
ATLAS Test Code

Specimen Information

Type

Red, Plain

Volume

1.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Frozen

Fasting Required?
False
Patient Instructions

Reference Range

5.0-20.0 µg/mL (this reference range is calculated from the therapeutic range of valproic acid that is approximately 10-20% unbound)

Methodology

Fluorescence Polarization

Clinical Significance

Detect use
Evaluate therapeutic effect or possible toxicity
Valproic acid is a broad-spectrum anticonvulsant drug used solely or in combination with other anticonvulsant drugs for the treatment of absence seizures. It also has demonstrated effectiveness in the management of generalized tonic-clonic and myoclonic seizures, as well as atypical absence, simple and complex partial and mixed grand mal and petit mal seizures. The capability of treating many types of seizures with a single anticonvulsant has resulted in the widespread use of valproic acid, particularly in children in whom tonic-clonic and myoclonic seizures are most prevalent. Valproic acid has proven effective in the treatment of many patients otherwise refractory to other anticonvulsant treatments. Most patients receiving valproic acid do not develop a tolerance to its anticonvulsant effects.
Valproic acid is rapidly absorbed orally with syrup peak levels reached in 15 minutes to 2 hours. Absorption of enteric-coated diavalproex is delayed one hour with peak levels occurring 1 to 4 hours after a single oral dose.
Free Valproic Acid serum levels should be obtained on the following occasions:
Two to four days following initiation of therapy
Two to four days following any change in valproic acid dosage or dosing interval
When other antiepileptic drugs are added or withdrawn
If a decrease in seizure control occurs
If physical or laboratory signs of toxicity occur
When noncompliance is suspectedTime to peak concentration varies with food intake and preparation:
Fasting:
– Syrup: 0.5-1 hour
– Capsule: About 2 hours
Non-fasting:
– Syrup: About 3 hours
– Capsule: About 8 hours

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