Human metabolism of phenothiazines to sulfoxides determined by a new high performance liquid chromatography--electrochemical detection method.

The metabolism of phenothiazine drugs may contribute to both their therapeutic and toxic actions by production of active metabolites in vivo. Idiosyncratic reactions or treatment failure may be a consequence of differing patterns of metabolism in different patients. In this report, a modification of our method for the detection of metabolites of phenothiazines is described, which also permits the simultaneous determination of sulfoxide metabolites in human plasma. Application of this method to human plasma identifies marked individual differences in patterns of phenothiazine metabolism.