Valproic Acid, Free and Total
Also known as: VPA-F
Use
This test is preferred for therapeutic drug management in patients with renal failure or conditions that may alter albumin concentrations. Monitoring free valproic acid is crucial in cases of altered or unpredictable protein binding capacity due to variable, dose-dependent protein binding and potential drug-drug interactions. Calculating percent free helps minimize differences in test cross-reactivity and aids in dose optimization. Adverse effects like headache, somnolence, and dizziness may occur.
Special Instructions
The timing of specimen collection should be a predose (trough) draw at steady-state concentration. After collection, separate serum from cells within 2 hours and transfer 2 mL serum to an ARUP standard transport tube. Minimum volume should be 1 mL.
Limitations
The test may not accurately reflect concentrations in patients with extremely abnormal protein binding or in those with significant drug-drug interactions affecting protein binding. Free valproic acid measurements should be interpreted in context with clinical findings.
New York Approved
Methodology
Immunoassay (EIA)
Biomarkers
LOINC Codes
- 4086-5
- 32283-4
- 4087-3
Result Turnaround Time
1-4 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2 mL
Minimum Volume
1 mL
Container
ARUP standard transport tube
Collection Instructions
Separate serum from cells within 2 hours of collection and transfer to transport tube.
Patient Preparation
Predose (trough) draw at steady-state concentration.
Storage Instructions
Refrigerated.
Causes for Rejection
Light blue (citrate), gray (oxalate), green (heparin), K2EDTA plasma, tubes with liquid anticoagulant, or gel separator tubes.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 24 hours |
| Refrigerated | 1 week |
| Frozen | 1 month |