Carbamazepine-10,11 Epoxide

CPT: 80339
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Test Details

Synonyms

  • Carbatrol®
  • Epitol®
  • Equetro®
  • Tegretol®
  • Tegretol®-XR

Use

Carbamazepine-10,11 epoxide has anticonvulsant activity similar to that of the parent compound. The half-life averages six hours and is 60% bound to protein.1 This heterocyclic (iminostilbene) compound has potent antiepileptic properties and is effective alone or with other antiepileptic drugs in partial seizures, especially complex partial seizures, generalized tonic-clonic seizures, and combinations of these seizure types. Carbamazepine generally is ineffective for absence, myoclonic, and atonic seizures. In children with symptomatic generalized epilepsy and continuous spike-and-wave discharge, these seizure types may develop (or tonic-clonic seizures may increase in frequency) with the use of carbamazepine.

Methodology

Liquid chromatography/tandem mass spectrometry (LC/MS-MS)

Reference Interval

Suggested range: 0.4−4.0 μg/mL

Additional Information

Leukopenia may be dose-related and necessitates stopping the drug if the absolute neutrophil count falls to <1000/mm³.2 Hyponatremia may occur, especially in older patients. Patients in the first month of pregnancy are at increased risk of neural tube defects. Carbamazepine may interfere with the actions of theophylline, oral contraceptives, oral anticoagulants, or doxycycline.

Specimen Requirements

Specimen

Serum or plasma

Volume

1 mL

Minimum Volume

0.6 mL

Container

Red-top tube or green-top (heparin) tube. Do not use a gel-barrier tube. The use of gel-barrier tubes is not recommended due to slow absorption of the drug by the gel. Depending on the specimen volume and storage time, the decrease in drug level due to absorption may be clinically significant. Transfer separated serum or plasma to a plastic transport tube.

Collection

Trough: immediately prior to net dose. Due to variability of absorption, the trough level may not represent the lowest drug level during the dosing interval; therefore, in some patients, multiple determinations may be necessary.

Storage Instructions

Room temperature

Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Gel-barrier tube; gross lipemia; hemolysis; icteric specimen

Clinical Information

Footnotes

1. Svinarov DA, Pippenger CE. Relationships between carbamazepine-diol, carbamazepine-epoxide, and carbamazepine total and free steady-state concentrations in epileptic patients: The influence of age. Dec; 18(6):660-665. 8946662
2. Engel J. Seizures and Epilepsy. Contemporary Neurology Series. Philadelphia, Pa: FA Davis Co;1989.

References

American Medical Association, Division of Drugs and Toxicology. Drug Evaluations Annual. Milwaukee, Wis: AMA;1992.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
716803 Carbamazepine-10,11 Epoxide 9415-1 716804 Carbamazepine-10,11 Epoxide mcg/mL 9415-1

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