The metabolism of chlorpromazine N-oxide in the rat.

1. The metabolism of chlorpromazine N-oxide was studied in female rats after a 20 mg/kg single oral dose. 2. Metabolites identified in both urine and faeces were chlorpromazine, 7-hydroxychlorpromazine, chlorpromazine sulphoxide, N-desmethylchlorpromazine and N-desmethylchlorpromazine sulphoxide. 3. Metabolites were separated by h.p.l.c. or g.l.c. prior to mass spectrometric analysis. The structures of the metabolites were confirmed by direct comparison of their mass spectra and chromatographic behaviours with those of authentic compounds. 4. Chlorpromazine N-oxide and any metabolite which retained the intact N-oxide function, such as chlorpromazine, N,S-dioxide, could not be identified in any of the extracts. 5. When 3H-chlorpromazine N-oxide was administered under the same conditions; approximately twice as much radioactivity was excreted in the faeces (52.1 +/- 9.7%) as in the urine (26.9 +/- 7.2%).