The Side-Effects of Fluphenazine Decanoate

Abstract

The unwanted effects of the phenothiazines can be divided into two categories; those effects which represent the pharmacodynamic actions of a particular drug and occur as a function of dosage and individual susceptibility; and the hyper-sensitivity reactions (Shepherd et al., 1968). This latter group of side-effects is relatively rare, and there is no suggestion in the literature that they occur more frequently with the injectable long-acting phenothiazines (LAP) than with the oral forms. With the first available long-acting phenothiazine (fluphenazine enanthate) motor side-effects were frequently observed, particularly during the first few days after injection (Millar and Daniel, 1967; Lowther, 1969; Malm, 1970). Initial studies have suggested that fluphenazine decanoate is less likely to produce these unwanted extrapyramidal effects (Neal and Imlah, 1968; Ayd, 1970). So far, however, no study has attempted to make a quantitative evaluation of the problem of side-effects in the clinical situation of longterm medication. Since both the therapeutic efficacy and the unwanted extra-pyramidal side-effects are dose-dependent, it is meaningless to measure the incidence of side-effects without also recording the therapeutic gain: a low incidence of side-effects might only reflect a non-therapeutic dose of medication. Further, any such study should be continued for at least two months after the last reduction in dosage, as it is well recognized that loss of clinical control may be postponed for many weeks after phenothiazines have been discontinued.