Long-term depot neuroleptic treatment with perphenazine decanoate. II. Different depot intervals in the last 6 months of a 12 month study of 42 drug monitored psychotic patients.

In order to investigate the feasibility of administering perphenazine decanoate (PD) at three week intervals the 42 patients participating in the previously reported open, prospective 12 month study were, after six months, treated according to the following scheme: 21 patients continued to receive injections every two weeks (group I), whereas in the remaining 21 patients the intervals between injections were extended to 3 weeks (group II). Both groups continued to respond equally well to therapy. Moreover it was observed that the mean daily dose of perphenazine was significantly reduced when using 3 weeks intervals. This study demonstrates that PD administered every 3 weeks is a safe and effective remedy for maintenance therapy in psychotic patients.