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Test Code CARBG Carbamazepine-10,11-Epoxide, Serum

Useful For

Monitoring patients exhibiting symptoms of carbamazepine toxicity whose total serum carbamazepine concentration is within the therapeutic range, but who may be producing significant levels of the active metabolite epoxide, which can accumulate to concentrations equivalent to carbamazepine

Profile Information

Test ID Reporting Name Available Separately Always Performed
CARTA Carbamazepine, Tot, S Yes Yes
1011E Carb-10,11-Epoxide, S No Yes

Method Name

CARTA: Homogeneous Microparticle Agglutination Immunoassay

1011E: High-Performance Liquid Chromatography (HPLC)

Reporting Name

Carbamazepine-10,11-Epoxide, S

Specimen Type

Serum Red

Specimen Required

Container/Tube: Red top

Specimen Volume: 2 mL

Collection Instructions: Draw blood 12 hours (trough value) after last dose.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 7 days
  Frozen  28 days
  Ambient  48 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Clinical Information

Carbamazepine is a common antiepileptic drug. It is a first-line drug for treatment of partial seizures and trigeminal neuralgia.


Carbamazepine is metabolized by the liver to carbamazepine-10,11-epoxide (CBZ10-11) which is pharmacologically active and potentially toxic. CBZ10-11 is, in turn, inactivated by hepatic conversion to a transdiol derivative.


CBZ10-11 may be responsible for the congenital abnormalities that are sometimes associated with the use of carbamazepine during early pregnancy. There have been cases of severe seizures exacerbation when serum epoxide levels were increased. Toxic levels of CBZ10-11 can occur during:

-Concomitant administration of other drugs that induce hepatic oxidizing enzymes (eg, most antiepileptic drugs [with the exception of valproic acid and the benzodiazepines], propoxyphene)

-Concomitant administration of drugs that inhibit its breakdown such as valproic acid, felbamate, and lamotrigine

-High-dose carbamazepine therapy, especially in combination with the above conditions

Reference Values


Therapeutic: 4.0-12.0 mcg/mL

Critical value: ≥15.0 mcg/mL



Therapeutic concentration: 0.4-4.0 mcg/mL

Toxic concentration: ≥8.0 mcg/mL

Day(s) and Time(s) Performed

CARTA: Monday through Sunday; Continuously

1011E: Tuesday; 11 a.m.

Analytic Time

Same day/1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

80156-Carbamazepine, Tot, S


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CARBG Carbamazepine-10,11-Epoxide, S In Process


Result ID Test Result Name Result LOINC Value
7467 Carb-10,11-Epoxide, S 9415-1
CARTA Carbamazepine, Tot, S 3432-2

NY State Approved



If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.