Plasma levels of fluphenazine during fluphenazine decanoate treatment in schizophrenia

Sidney S. Chang, Javid I. Javaid, Maurice W. Dysken, Regina C. Casper, Philip G. Janicak

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


The authors measured plasma fluphenazine levels in 20 schizophrenic patients receiving 25 or 50 mg fluphenazine decanoate (FPZ-D) by IM injection every 2 weeks. The plasma levels were determined by a sensitive gas-liquid chromatographic (GLC) assay with a nitrogen detector device developed in their laboratory. Using this chemical assay method, they replicated the finding of a sharp initial plasma peak within 24 h after the injection followed by a low but rather stable plasma level as previously reported by nonchemical assay methods. The interval plasma levels (averages of day 4-10 after injection) ranged from 0.17-0.61 ng/ml in 10 patients who received 25 mg; and 0.20-0.93 ng/ml in 7 patients who received 50 mg FPZ-D every 2 weeks. This four-fold variation in plasma levels during FPZ-D injection was smaller than previously reported levels achieved with oral antipsychotic drug treatment. Based on the study of plasma levels achieved with FPZ-D injection and oral FPZ-H (fluphenazine HCl) in 6 patients, the dosage requirement of FPZ-D appeared to be difficult to predict from the oral dosage of FPZ-H in the same patient. Two weeks past injection, fluphenazine was undetectable in approximately half the samples with the GLC method. Thus, radioimmunoassay or radioreceptor assay, which also measures metabolites, might be more suitable for the study of plasma levels in patients receiving FPZ-D injection.

Original languageEnglish (US)
Pages (from-to)55-58
Number of pages4
Issue number1
StatePublished - Sep 1985


  • Fluphenazine decanoate
  • Fluphenazine hydrochloride
  • GLC
  • Individual variation
  • Initial peak
  • Low plasma levels
  • Oral and injectable
  • Plasma fluphenazine


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