AUTOMATED-DETERMINATION OF CLOZAPINE AND MAJOR METABOLITES IN SERUM AND URINE

Clozapine is an atypical neuroleptic that is increasingly used for the treatment of schizophrenia. An automated method was developed for the routine quantification of clozapine and its major metabolites, N-desm ethylclozapine and clozapine N-oxide, in human serum and urine by colu mn switching and online high-performance liquid chromatography with ul traviolet detection. The method included adsorption of clozapine and i ts metabolites on a cyanopropyl-coated clean-up column (10 mu m; 10 mm x 4.0 mm ID), washing interfering serum constituents to waste by deio nized water, and, after column switching, separation on C18 ODS Hypers il reversed-phase material (5 mu m; 250 mm x 4.6 mm ID). The compounds of interest were separated and eluted in fewer than 20 minutes, using a mobile phase consisting of 37.5 acetonitril:62.5 water, containing 0.4% (vol/vol) tetramethylethylenediamine and adjusted to pH 6.5 with concentrated acetic acid. Ultraviolet-detection was performed at 354 n m. The determinations exhibited linearity between detector signal and drug concentrations in a range from 5 ng/ml to 50 mu g/ml. As little a s 10 ng/ml of clozapine and 20 or 30 ng/ml of the metabolites was quan tifiable. Interferences with other psychotropic drugs, serum, or urine constituents were negligible. The automated procedure enables the ana lysis of clozapine and metabolites in serum or urine in less than 1 ho ur.