DECOMPOSITION OF CLOZAPINE N-OXIDE IN THE QUALITATIVE AND QUANTITATIVE-ANALYSIS OF CLOZAPINE AND ITS METABOLITES

Pooled plasma from healthy volunteers was spiked with pure, synthetic clozapine or clozapine N-oxide and then made alkaline with either sodi um hydroxide or sodium carbonate. The alkalized samples were allowed t o stand at room temperature for various time intervals before extracti on with organic solvent and then analyzed by high-performance liquid c hromatography. It was found that clozapine N-oxide was reduced to cloz apine in plasma made alkaline with sodium hydroxide, but such reductio n was negligible in the plasma made alkaline with sodium carbonate. Th e amount of clozapine produced from clozapine N-oxide depended upon bo th the strength of the alkali added to the plasma and the duration of exposure of the plasma proteins plus clozapine N-oxide to the alkali. The reduction appears to take place through reducing equivalents gener ated by the action of strong alkali on plasma proteins. The thermal la bility of clozapine N-oxide during gas chromatography-mass spectrometr ic analysis was also investigated. It was found that clozapine N-oxide was quantitatively decomposed to clozapine during gas chromatography- mass spectrometric analysis.