Haloperidol decanoate and flupenthixol decanoate in schizophrenia. A long-term double-blind cross-over comparison. Zuclopenthixol decanoate and haloperidol decanoate in chronic schizophrenia: a double-blind multicentre study. Haloperidol decanoate v. fluphenazine decanoate as maintenance therapy in chronic schizophrenic in-patients. Minimal effective dose and relapse--double-blind trial: haloperidol decanoate vs. placebo.
Thirty-two schizophrenic patients, previously treated with antipsychotics, were treated with haloperidol decanoate and flupenthixol decanoate in a double-blind cross-over study. The drugs were given for 24 weeks each at an individually adapted dose. The last three injections of either drug were given at fixed 4-week intervals. The mean dose over the two treatment periods changed from 131 mg (start) to 151 mg (week 24) in the haloperidol decanoate group and from 56 mg to 66 mg in the flupenthixol decanoate group, the inter-drug ratio being 2.3:1. During the first study period, the patients' condition remained rather stable with both drugs. After crossing-over, the symptoms were further reduced with haloperidol decanoate but increased with flupenthixol decanoate. Side effects of the two drugs were comparable and were generally few and mild. It was concluded that 4-week intramuscular administration of haloperidol decanoate provides appropriate control of schizophrenic symptoms, but that flupenthixol decanoate should be dosed at shorter intervals. Zuclopenthixol decanoate (ZPT-D) and haloperidol decanoate (HAL-D) were compared in the maintenance treatment of chronic schizophrenic patients. All patients were treated with either ZPT-D or HAL-D for at least 3 months and were then randomly allocated to treatment with either ZPT-D (100-600 mg every 4 weeks) or HAL-D (38-200 mg every 4 weeks) for 9 months. Sixty-four patients entered the study. Three patients were only assessed at baseline. Four patients in the HAL-D group were withdrawn because of deterioration. One patient in the ZPT-D group committed suicide. Fifty-six patients completed the trial. The assessment programme comprised Clinical Global Impressions by psychiatrists and nurses, the Brief Psychiatric Rating Scale (BPRS), Montgomery-Asberg Depression Rating Scale (MADRS), UKU Side Effect Scale and Simpson-Angus Scale, Ratings were made at baseline and after 12, 24 and 36 weeks of treatment. The severity of illness scores remained almost constant. The only between-group difference was recorded at month 6 in favour of ZPT-D. The BPRS total scores were reduced significantly in both groups with no between-group differences. The depression scores on the MADRS were very low. Both treatments caused few and mild side effects according to the UKU Side Effect Scale and the Simpson-Angus scale, and there were no significant differences between the groups. Both ZPT-D and HAL-D seem to be effective in the maintenance treatment of chronic schizophrenic patients and cause few side effects. The injections of ZPT-D and HAL-D can be given at 4-week intervals. 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. Fifty-six chronic schizophrenic patients were randomized into haloperidol decanoate (HD) or placebo groups for 48 weeks of double-blind treatment. The double-blind trial was preceded by a 15-week single-blind run-in period, during which all patients were treated with 60 mg of HD (approximately corresponding to 3.6 mg orally/day) every fourth week (except for the second injection, which was given after 3 weeks). Eight relapses occurred during the run-in period, and seven other patients refused further participation. The remaining 41 patients were then treated double blind, either with HD, 60 mg/4 weeks (18 patients), or with placebo (23 patients). Two patients (11%) in the HD group and 16 (69%) in the placebo group relapsed during the 48-week double-blind period. The plasma concentrations of haloperidol were measured every fourth week in both groups. Steady state was reached after 11 weeks. The mean steady-state level was 6.3 nmol/L. In the placebo group, a 50% decrease in the mean haloperidol plasma concentration was seen 8 weeks after withdrawal of haloperidol. The haloperidol plasma concentration was a predictor of relapse. There was no statistical difference between the treatment groups regarding extrapyramidal symptoms. More biperiden, however, was used in the HD group, while the placebo patients took more sedatives. The results of this study show that the relatively low and fixed dose of 60 mg of HD every fourth week was superior to placebo in preventing relapse in schizophrenia.(ABSTRACT TRUNCATED AT 250 WORDS)
Haloperidol decanoate may have a substantial effect in improving the symptoms and behaviour associated with schizophrenia in comparison to placebo, but data are remarkably sparse. 
There are no discernible differences between the depot form of haloperidol and its oral equivalent. For those needing and willing to take the drug, the means of administration is then a matter of individual choice and clinical judgement. As there are no clear differences between haloperidol decanoate and other depots, the choice of depot medication could also be individually tailored and patient preference exercised.
Well-conducted and reported randomised trials are needed comparing haloperidol decanoate with other depots but the comparison of haloperidol decanoate to oral antipsychotics is a priority.