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HelpTest ID CARBG Carbamazepine-10,11-Epoxide, Serum
Useful For
Monitoring patients exhibiting symptoms of carbamazepine toxicity whose serum carbamazepine concentration is within the therapeutic range, but who may be producing significant levels of the active metabolite epoxide
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:
Immunoassay
1011E: High-Performance Liquid Chromatography (HPLC)
Reporting Name
Carbamazepine-10,11-Epoxide, SSpecimen Type
Serum RedContainer/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 |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 14 days |
| Ambient | 14 days | |
| Frozen | 14 days |
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
CARBAMAZEPINE, TOTAL
Therapeutic: 4.0-12.0 mcg/mL
Critical value: > or =15.0 mcg/mL
CARBAMAZEPINE-10,11-EPOXIDE
Therapeutic concentration: 0.4-4.0 mcg/mL
Toxic concentration: ≥8.0 mcg/mL
Cautions
Routine determination of carbamazepine-10,11-epoxide (CBZ10-11) is not clinically indicated. It should be considered when the source of treatment in associated symptoms is not obvious.
Day(s) Performed
CARTA: Monday through Sunday; Continuously
1011E: Wednesday; 11 a.m.
Report Available
Same day/1 dayPerforming Laboratory
Mayo Medical 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, total
80299-Carbamazepine-10,11-Epoxide