Carbamazepine - plasma or serum

Last updated: Tuesday, 30, March, 2004

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Item Process

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


Immunoassay, HPLC.

Therapeutic Interval

20-40 µmol/L (6-12 mg/L).


Therapeutic drug monitoring.


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

Mean half-life is 35 hours (range 18-65 hours) early in treatment, often becoming shorter (12-24 hours) 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.


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

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