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Carbamazepine Epoxide Level (including CBZ)

Carbamazepine-Epoxide, Carbamazepine Metabolite

Test Codes

Antrim #19129, EPIC: LAB5379, SOFT: CAREP

Department

Toxicology

Specimen Collection Criteria

Collect: One plain Red-top tube. (Minimum Whole Blood: 2.0 mL)

Do not use Serum Separator Tubes.
Time of Collection: Trough, just prior to the next dose.
Record the exact time of specimen collection on the tube or in the computer system.

Physician Office/Draw Specimen Preparation

Let specimens clot 30-60 minutes. Centrifuge specimen to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube within two hours of collection. (Minimum: 0.5 mL serum)

Preparation for Courier Transport

Transport: Centrifuged collection tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL serum)

Rejection Criteria

• Serum Separator (SST) tubes.
• Severely lipemic or hemolyzed specimens. 

In-Lab Processing

Let specimens clot 30-60 minutes. Centrifuge specimen to separate serum from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 72 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Frozen (-20°C/-4°F or below): 2 months

Laboratory

Royal Oak Toxicology Laboratory

Performed

Monday, Wednesday, Friday.
Results available the same day as testing performed (1-3 days).

Reference Range

Carbamazepine:
Therapeutic Range: 6-12 mcg/mL.
Toxic Range: 15 mcg/mL.

Carbamazepine-Epoxide:
Therapeutic Range: 1.0-4.0 mcg/mL.
Toxic Range: 7.0 mcg/mL.

This test was developed and its performance characteristics determined by Beaumont Health. It has not been cleared or approved by the FDA. The Laboratory is regulated under CLIA as qualified to perform high-complexity testing. This test is used for clinical purposes and should not be regarded as investigational or for research.

Test Methodology

Total Carbamazepine: Particle Enhanced Turbidimetric Inhibition Immunoassay.
Carbamazepine Epoxide: Liquid Chromatography/Tandem Mass Spectrometry (LC-MS/MS).

Interpretation

This assay includes a measurement of total carbamazepine. Carbamazepine epoxide levels may be increased by comedication with metabolic inducing agents, such as phenytoin or phenobarbital, or by inhibitors of epoxide hydrolase, such as valproic acid.

Clinical Utility

This assay is useful for monitoring patients exhibiting symptoms of carbamazepine toxicity.

CPT Codes

80375 (alternate: G0480).
LOINC: 9415-1

Contacts

Last Updated

1/26/2023