Pharmacokinetic and pharmacodynamic studies on high doses of fluphenazine

Six chronic schizophrenics--earlier refractory to recommended doses of neuroleptic drugs but eventually responding to 250 mg fluphenazine heptanoate weekly--participated in a pharmacokinetic study. Five out of the six patients showed rather constant steady state plasma fluphenazine values on a 250 mg depot weekly. After depot drug withdrawal, the single oral dose pharmacokinetics on 400 mg fluphenazine showed the same variations in Cmax, tmax, t 1/2 and AUC as are observed when recommended doses of fluphenazine are used. We thus could not demonstrate any dose-dependent pharmacokinetics on high oral fluphenazine doses. In half the patients, a biphasic decay in the plasma concentration curve indicated at least two compartments. The patients were then studied for up to 2 years on 200-500 mg fluphenazine as a single daily dose. The fluphenazine plasma levels were rather constant in the individual patients during this period. The plasma prolactin values were related to the fluphenazine values even in the high value area, thus showing a persistent pharmacodynamic variation capacity. The clinical part of the study did not show any relevant findings.