Autoinduction of the metabolism of phenothiazine neuroleptics in a primary culture of human hepatocytes.

Background: The metabolism of phenothiazine neuroleptics (promazine, perazine) in a primary culture of human hepatocytes after pretreatment of cells with those neuroleptics was studied.

Methods: The hepatocytes were pretreated with 25 μM promazine or perazine for 96 h. Then, the cells were incubated for 2, 4, 6, 8 and 24 h in the presence of neuroleptics. At the indicated time points, concentrations of phenothiazines and their metabolites (5-sulfoxides and N-desmethyl derivatives) were measured in the culture medium using HPLC with UV detection.

Results: Pretreatment of the primary culture of human hepatocytes with promazine or perazine resulted in accumulation of their metabolites in the culture medium. Such an effect was not observed in the case of control cultures (not pretreated with neuroleptics).

Conclusion: The obtained results suggest that the tested phenothiazines may stimulate their own metabolism by inducing CYP1A2, CYP3A4 and CYP2C19 isoforms.