Low neuroleptic serum levels in patients receiving fluphenazine decanoate

Abstract

Serum levels of fluphenazine in 9 patients were monitored following injections of fluphenazine decanoate ranging from 10-75 mg. Levels were detected by a radioreceptor assay based on the ability of the drug to compete with 3H-spiroperidol for binding to dopamine receptors in rat caudate membranes. Serum levels of fluphenazine were quite stable over a 2-3 wk period following single i.m. injections of the decanoate and correlated with injected dose. Following decanoate treatment serum levels of fluphenazine are substantially lower than levels observed for most other neuroleptics administered orally. This raises questions as to how fluphenazine decanoate exerts therapeutic actions.