Carbamazepine level

Keywords: Tegretol

Specimen:

5 mL blood in lithium heparin or plain tube, collected immediately prior to the next dose.

Method:

Immunoassay, HPLC.

Therapeutic Interval:

20-40 µmol/L (6-12 mg/L).

Application:

Therapeutic drug monitoring.

Interpretation:

Levels are related to the dose and the time since the previous dose.

Mean half-life is 35 h (range 18-65 h) early in treatment, often becoming shorter (12-24 h) with prolonged treatment due to enzyme induction by the drug (autoinduction).

Carbamazepine epoxide, a major metabolite, is also active pharmacologically. Its level may be available if analysis is done by HPLC.

Reference:

Monaco F et al. J Int Med Res 1979; 7: 152-157.

Glauser TA and Pippenger CE. Epilepsia. 2000; 41:6-15.