Determination of clobazam and its N-demethyl metabolite in serum of epileptic patients.

We describe a gas-liquid chromatographic method, using a nitrogen-specific detector, which is suitable for the simultaneous quantitation of clobazam and its main metabolite N-demethyl clobazam in the serum of epileptic patients treated with other anticonvulsant co-medication. Flunitrazepam (internal standard) is added to the sample and after extraction with a toluene/ethyl acetate mixture (3 + 1 by vol), the organic extract is evaporated and the residue is reconstituted in a small volume of solvent and chromatographed on a 3% SP2250 column. The sensitivity limits are about 2 to 5 micrograms per liter of original sample.