The initiation of long-term pharmacotherapy in schizophrenia: dosage and side effect comparisons between oral and depot fluphenazine

Abstract

This report focuses on two comparisons between oral and depot fluphenazine specifically FPZ decanoate: 1) can equivalent dosages for the two drugs be established and do these equivalencies change over six months of treatment; 2) what are the side effects seen with the two drugs during the early weeks of administration. Patients in the study receive either oral or depot FPZ as the active treatment but in order to preserve double blind conditions, they are also given the other treatment in placebo form. No dosage equivalence is established by the protocol, however, if dosage is adjusted, both forms must be changed and in the same direction. During the first weeks of treatment there is a linear relationship between the two dosage forms but a range of relatively low dosages of the oral compound (5-20 mg) is associated with a single dose (25 mg/q 3 weeks) of FPZ decanoate. At higher dosages of the oral drug the relationship is linear. Side effects of some kind are noted in over 60 percent of patients in both treatment groups after four weeks of treatment, while symptoms of at least moderate severity occur in almost 40 percent. Only symptoms involving the extrapyramidal system and sleep disturbance are observed in more than 20 percent of the patients. Benztropine was prescribed only if needed and was administered to 65% of patients. In general, those receiving benztropine had more side effects than those who did not. These differences reached significance for extrapyramidal symptoms and depression. Based on these data, we conclude that at the dosages used in this study there are no side effect differences between these two forms of fluphenazine in the early weeks of administration. Dosage equivalence between the two drugs can be set within the range of 5-60 mg/day oral and 12.5-100 mg/three weeks depot.