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Valproic Acid Total and Free

Depakene^®, Depakote^®, Valproate, Valproex^®, Divalproes, Dipropyl acetic acid, Epilim, Valparin, Vilapro, Stavzor, XVALF

Test Codes

EPIC: LAB172, Beaker: VPA Free&Tot, CHW: LAB172

NOTE: Due to no weekend delivery. Specimens received in lab between Friday and Sunday will not be sent out until Monday.

Department

Send Outs

Specimen Collection Criteria

Collect (preferred specimen): One Green-top Lithium Heparin.

Also acceptable: One Gold-top SST tube.

Physician Office/Draw Specimen Preparation

Let specimens clot 30-60 minutes and centrifuge to separate plasma or serum from cells within two hours of collection. Transfer 4.5 mL of plasma or serum to plastic transport tube and refrigerate (2-8°C or 36-46°F). (Minimum: 2.0 mL)

Preparation for Courier Transport

Transport: Plasma or serum in plastic transport tube, refrigerated (2-8°C or 36-46°F). (Minimum: 2.0 mL)

Rejection Criteria

Specimens not collected and processed as indicated.

In-Lab Processing

Let specimens clot 30-60 minutes and centrifuge to separate plasma or serum from cells within two hours of collection. Transfer 4.5 mL of plasma or serum to plastic transport tube and refrigerate (2-8°C or 36-46°F). (Minimum 2.0 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 8 hours
Refrigerated (2-8°C or 36-46°F): 24 hours (48 hours if aliquoted plasma/serum)
Frozen (-20°C/-4°F or below): Aliquot plasma/serum for longer storage

Specimen Storage in Department Prior to Disposal: 72 hours

Laboratory

Sent to Corewell Health Reference Laboratory, Grand Rapids, MI.

Performed

Sunday – Saturday, 24 hours a day.
Results available within 1 day.

Reference Range

% Bound Valproic Acid
87-93 %

% Free Valproic Acid
7-13 %

Free Valproic Acid
5-15 ug/mL

Total Valproic Acid
50-100 ug/mL

Test Methodology

Homogenous Enzyme Immunoassay

Interpretation

Valproic Acid is susceptible to concentration-dependent plasma protein binding. Increases in plasma or serum concentrations will likely result in increased drug clearance. Valproic Acid will also compete for plasma protein binding sites and has been shown to decrease the binding of other highly bound drugs. Valproic Acid may inhibit the oxidative metabolism of co-administered medications.

Clinical Utility

Valproic acid is a broad-spectrum anticonvulsant drug used alone to treat simple and complex absence seizures and in combination with other anticonvulsant drugs for control of generalized seizures that include absence seizures. This assay is used to monitor the therapeutic drug level and evaluate the toxicity of valproic acid.

CPT Codes

80164, 80165

Contacts

Last Updated

8/19/2025