Fluphenazine plasma levels in patients receiving low and conventional doses of fluphenazine decanoate

Abstract

Plasma fluphenazine concentrations (FLU) were measured in 45 patients with schizophrenic disorders who participated in a double-blind comparison of 5 and 25 mg fluphenazine decanoate (FD). The rise in plasma level of FLU 24 h after a "test dose" was significantly correlated with steady state FLU concentration at 12 weeks (for 5 mg patients, r = 0.45, P = 0.04; for 25 mg, r = 0.78, P = 0.005). Patients who had low FLU at baseline required nearly 6 months to reach a steady state when they received 25 mg. Patients who received 5 mg and had low FLU at baseline continued to demonstrate relatively low plasma levels for the entire 1st year. Although the mean FLU at 6 months was lower for patients who relapsed during the subsequent 18 months (0.57 ng/ml for relapsers vs 1.01 ng/ml for nonrelapsers), this difference was not statistically significant. When plasma levels from both dosage groups were combined, FLU at 12 weeks correlated significantly with factor scores for akinesia (r = 0.52, P = 0.002) and BPRS cluster scores for retardation (r = 0.52, P = 0.002). These results indicate that the measurement of fluphenazine plasma levels may be useful in determining when patients treated with FD are receiving drug doses which are likely to cause discomforting side effects.

The sulfoxidation of fluphenazine in schizophrenic patients maintained on fluphenazine decanoate

“…The rise in mean plasma levels of fluphenazine in patients receiving the 25 mg dose ( Fig. 2A) over a period of 6 months is consistent with our previous report that it took 3-6 months to reach steady state on this dosage regimen (Marder et al 1986). In contrast, there was a decline in mean plasma levels of the sulfoxide over the same time period in the high dose patients (Fig.…”

Pharmacological Treatment of Substance-abusing Schizophrenic Patients

“…Chief among these is that the long half-life of these compounds makes dose titration difficult. Since steady-state levels may not be achieved for 6 months with depot neuroleptics (Marder et al 1986), plasma concentrations may creep up (or down) during this interval following dosage changes, without the clinician’s realizing that the patient’s true exposure to medication effects is changing despite a seemingly steady rate of administration. The use of depot neuroleptics is also complicated by the fact that conversion values between oral neuroleptics and their depot counterparts are less than perfectly worked out (Schooler et al 1980; Yadalam and Simpson 1988).…”

Pharmacokinetics of long-acting injectable neuroleptic drugs: clinical implications

“…Thus, in one study, patients receiving biweekly injections of 5 mg fluphenazine decanoate were found to have reached steady state after the first injection because of fluphenazine resulting from prior therapy with fluphenazine decanoate administered before the period of study. On the other hand, patients receiving biweekly injections of 25 mg fluphenazine decanoate appeared to require 3-6 months (6-12 injections) to reach steady state (Marder et al 1986). Similarly, in a group of patients treated with weekly injections of 50 mg fluphenazine decanoate, 10 weeks (ten injections) were required to reach steady state (Ereshefsky et al 1984) although from theoretical considerations, these authors predicted a time to steady state of 4-6 weeks.…”