Carbamazepine-10, 11 Epoxide and Total Carbamazepine (Sendout)

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.

Ordering Note: If both Carbamazepine and metabolite Carbamazepine-10,11-Epoxide are requested, order Carbamazepine (Tegretol) [CBAM] along with this test.

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

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 < or =0.2 mcg/mL in symptomatic adults and < or =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.

6 mL blood in RED TOP tube

Unacceptable: Any other tube type, including gel tubes.

Outside Laboratories: Centrifuge sample and transfer serum to a separate plastic vial. Refrigerate serum.

Stability: Refrigerated (preferred): 7 days; Frozen: 28 days; Ambient: 48 hours.

Reject Due To: Gross hemolysis, gross lipemia, gross icterus.

Centrifuge sample and transfer serum to a separate plastic vial. Refrigerate serum.

Sendouts:

• Order Mayo Test: CARBG.
• Interfaced: Yes.

Stability: Refrigerated (preferred): 7 days; Frozen: 28 days; Ambient: 48 hours.

Reject Due To: Gross hemolysis, gross lipemia, gross icterus.