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HelpTest ID CARTF Carbamazepine Profile, Serum
Specimen Required
Container/Tube: Red top
Specimen Volume: 2 mL
Submission Container/Tube: Plastic vial
Collection Instructions:
1. Draw blood 12 hours (trough value) after last dose.
2. Centrifuge and aliquot serum into a plastic vial within 2 hours of collection.
Forms
If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.
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
Free carbamazepine concentration may also be useful to monitor in patients with altered or unpredictable protein binding capacity
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CARTA | Carbamazepine, Tot, S | Yes | Yes |
| 1011E | Carb-10,11-Epoxide, S | No | Yes |
| CARF | Carbamazepine, Free, S | Yes | Yes |
Method Name
CARTA: Homogeneous Microparticle Agglutination Immunoassay
1011E: High-Performance Liquid Chromatography (HPLC)
CARF: Ultrafiltration Followed by Homogeneous Microparticle Agglutination Immunoassay
Reporting Name
Carbamazepine Profile, SSpecimen Type
Serum RedSpecimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 7 days |
| Frozen | 28 days | |
| Ambient | 48 hours |
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: ≥15.0 mcg/mL
CARBAMAZEPINE-10,11-EPOXIDE
Therapeutic: 0.4-4.0 mcg/mL
Toxic concentration: ≥8.0 mcg/mL
CARBAMAZEPINE, FREE
Therapeutic: 1.0-3.0 mcg/mL
Critical value: ≥4.0 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, CARF: Monday through Sunday
1011E: Tuesday
Report Available
Same day/1 to 7 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
80156-Carbamazepine, total
80157-Carbamazepine, free
80161-Carbamazepine-10,11-Epoxide