Plasma levels of neuroleptic in patients receiving depot fluphenazine.

Depot forms of fluphenazine are frequently used in the outpatient treatment of psychiatric patients. To gather relevant data on pharmacokinetic characteristics of depot fluphenazines, the authors measured plasma levels of neuroleptic activity in 76 clinic patients on stable dosage regimens of fluphenazine decanoate or fluphenazine enanthate. Dose and plasma neuroleptic activity level were highly correlated for both forms of depot fluphenazine. Furthermore, the slope of the regression of log dose to the log plasma neuroleptic activity was the same for both drug forms. However, doses of enanthate twice those of decanoate were associated with the same mean plasma level of neuroleptic activity. Finally, while blood levels of drug overlapped markedly in cohorts of patients receiving different doses of depot medication, the assumption of recent studies that, on the average, patients in such cohorts have different blood and tissue levels of drug was confirmed.