Long-term depot neuroleptic treatment with perphenazine decanoate. I. Efficacy and side effects in a 12 month study of 42 drug monitored psychotic patients.

In an open, prospective 12 month study of perphenazine decanoate (PD), 42 psychotic patients diagnosed according to DSM-III were treated with a fixed depot interval and an individual dose, guided by gas chromatographic perphenazine plasma concentration monitoring combined with clinical evaluation. Degree of illness was rated using a social-psychiatric CGI-scale and extrapyramidal side effects were evaluated by means of a modified Simpson and Angus rating scale. After six months of treatment, a statistically significant improvement was found (p less than 0.001). During the last six months a further slight reduction in mean CGI-scores was observed. Mild to moderate extrapyramidal side effects occurred in 9 patients (21%) principally during the initial phase of therapy. No other side effects or changes in blood chemistry were found during the study. Plasma concentrations of perphenazine increased during the initial 3 months and stabilized hereafter. There were however, large intra- and inter-individual variations in the perphenazine plasma concentration/dose ratio. In addition, it was observed that plasma concentrations of perphenazine were significantly higher in patients who had been treated with neuroleptics for more than 10 years compared to those who had been treated 5 years or less. This observation indicates gradual development of tolerance to neuroleptic treatment. This study demonstrates that PD is a safe and effective remedy for maintenance therapy in psychotic patients.