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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


Collection Container/Tube: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 2 mL

Collection Instructions:

1. Draw blood 12 hours (trough value) after last dose.

2. Centrifuge and aliquot serum into a plastic vial.


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

Reference Values

CARBAMAZEPINE, TOTAL

Therapeutic: 4.0-12.0 mcg/mL

Critical value: ≥15.0 mcg/mL

 

CARBAMAZEPINE-10,11-EPOXIDE

Therapeutic concentration: 0.4-4.0 mcg/mL

Toxic concentration: ≥8.0 mcg/mL

Interpretation

The clinically acceptable serum concentration of carbamazepine-10,11-epoxide (CBZ10-11) is not well established, but 4.0 mcg/mL has often been used as an upper limit for its therapeutic range.

 

The ratio of CBZ10-11 to carbamazepine is usually ≤0.2 mcg/mL in symptomatic adults and ≤0.3 mcg/mL in children.

 

Clinical correlation is aided by comparing values obtained when the patient is symptomatic with those obtained when the patient has improved.

Clinical Reference

1. Theodore WH, Narang PK, Holmes MD, et al: Carbamazepine and its epoxide: relation of plasma levels to toxicity and seizure control. Ann Neurol 1989;25:194-196

2. Tomson T, Almkvist O, Nilsson BY, et al: Carbamazepine-10, 11-epoxide in epilepsy. A pilot study. Arch Neurol 1990;47:888-892

3. McKauge L, Tyrer JH, Eadie MI: Factors influencing simultaneous concentrations of carbamazepine and its epoxide in plasma. Ther Drug Monit 1981;3:63-70

4. Brodie MJ, Forrest G, Rapeport WG: Carbamazepine-10,11-epoxide concentrations in epileptics of carbamazepine alone and in combination with other anticonvulsants. Br J Clin Pharmacol 1983;16:747-749

5. Shoeman JF, Elyas AA, Brett EM, Lascelles PT: Correlation between plasma carbamazepine-10,11-epoxide concentration and drug side-effects in children with epilepsy. Dev Med Child Neurol 1984;26:756-764

Day(s) Performed

CARTA: Monday through Sunday

1011E: Tuesday

Report Available

Same day/1 to 7 days

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. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80156-Carbamazepine, Tot, S

80161-Carbamazepine-10,11-Epoxide 

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CARBG Carbamazepine-10,11-Epoxide, S 50337-5

 

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

Forms

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