The analysis of clobazam and its metabolite desmethylclobazam by high-performance liquid chromatography

The analysis of clobazam and its metabolite desmethylclobazam by high-performance liquid chromatography is described. After adding an internal standard 500 microliters of plasma is extracted under basic conditions into dichloroethane. The organic solvent is then evaporated to dryness and the residue reconstituted in 100 microliters of mobile phase prior to injecting an aliquot (30 microliters) onto a Hypersil 5 MOS column, which is eluted with acetonitrile/acetate buffer (pH 5.4) 40:60 vol/vol. The components are separated in approximately 12 min. Using this method, 15 micrograms L-1 of clobazam and 30 micrograms L-1 of desmethylclobazam can be detected. The method is suitable for the therapeutic monitoring of these two drugs in patient samples.