Comparative Effectiveness of Fluphenazine Decanoate Injections Every 2 Weeks Versus Every 6 Weeks

OBJECTIVE: Dose reduction strategies for the maintenance treatment of schizophrenia are designed to maintain the benefits of antipsychotic drug therapy while reducing risks. Previous strategies with decanoate preparations have been based on the use of lower doses per injection to achieve dose reduction; these strategies have achieved dose reduction but have resulted in some increase in symptoms. The authors tested a new dose reduction approach: increasing the interval between injections during intramuscular decanoate antipsychotic treatment. METHOD: Fifty outpatients with schizophrenia or schizoaffective disorder were randomly assigned to receive 25 mg of fluphenazine decanoate intramuscularly either every 2 weeks or every 6 weeks for 54 weeks in a double-blind design. RESULTS: The two dose regimens did not differ significantly in relapse, symptom, or side effect measures. The every-6-weeks regimen was associated with a significant reduction in total antipsychotic exposure. CONCLUSIONS: The use of injections every 6 weeks instead of every 2 weeks may increase compliance and improve patients’ comfort as well as decrease cumulative antipsychotic exposure, without increasing relapse rates or symptoms. (Am J Psychiatry 1999; 156:412–418)