Haloperidol decanoate v. fluphenazine decanoate as maintenance therapy in chronic schizophrenic in-patients.

In a double-blind study of 38 chronic schizophrenic in-patients, haloperidol decanoate was compared with fluphenazine decanoate as maintenance therapy over 60 weeks. Both drugs were given by injection at 4-week intervals. Haloperidol and fluphenazine were assumed to be equipotent; the mean starting dose of the former was 127 mg and of the latter 106 mg. The number of withdrawals over 60 weeks was similar in both groups but relapses, strictly defined, were significantly more frequent in the haloperidol group. When patients were switched to haloperidol, Parkinsonism diminished more quickly than in the fluphenazine group, but after 60 weeks there was no difference in severity in the two drug groups. The higher relapse rate and the quicker reduction in Parkinsonism in the haloperidol group might be due to a misjudgement in equivalent doses of the two drugs. Plasma haloperidol steady state levels were reached in most patients by 8-12 weeks. Plasma neuroleptic and prolactin levels, week-by-week systemic drug availability and Parkinsonism showed less variation between injections with haloperidol than with fluphenazine.