Depot perphenazine decanoate and enanthate for schizophrenia

Anti-psychotic drugs are usually given orally but compliance with medication given by this route may be difficult to quantify. The development of depot injections in the 1960s gave rise to extensive use of depots as a means of long-term maintenance treatment. Perphenazine decanoate and enanthate are depot antipsychotics that belong to the phenothiazine family and have a piperazine ethanol side chain.

To assess the effects of depot perphenazine decanoate and enanthate versus placebo, oral anti-psychotics and other depot antipsychotic preparations for people with schizophrenia in terms of clinical, social and economic outcomes.

Biological Abstracts (1982-1998), the Cochrane Library (Issue 2, 1998), the Cochrane Schizophrenia Group's Register (June 1998), EMBASE (1980-1998), MEDLINE (1966-1998), and PsycLIT (1974-1998) were searched. References of all identified trials were also inspected for more studies and industry contacted.

Randomised clinical trials focusing on people with schizophrenia where depot perphenazine decanoate and enanthate, oral anti-psychotics or other depot preparations were compared.

Studies were reliably selected, quality rated and data extracted. For dichotomous data Peto odds ratios (OR) with the 95% confidence intervals (CI) were estimated. Where possible, the number needed to treat statistic (NNT) was calculated. Analysis was by intention-to-treat.

One study of six months duration, compared perphenazine enanthate to clopenthixol decanoate. There was no differences between the two for outcomes of global improvement, relapse and leaving the study early. More people in the perphenazine enanthate group required anticholinergic drugs than those allocated to clopenthixol decanoate (OR 3.6 CI 1.2-10, NNT 10). A single study (n=64, duration six weeks) compared perphenazine enanthate and its longer acting decanoate ester. Data on relapse and leaving the study early failed to show convincing differences. The enanthate group, however, experienced more movement disorders (OR 0.2 CI 0.06-0.7) than those allocated the decanoate ester of the same drug (NNT 4.0) and required more anticholinergic drugs (OR 0.2 CI 0.08-0.7, NNT 3.7).

Depot perphenazine is in clinical use in the Nordic countries, Belgium, Portugal and the Netherlands. At a conservative estimate a quarter of a million people suffer from schizophrenia in those countries and could be treated with depot perphenazine. The total number of participants in the two trials with useful data is 236. Neither study observes the effect of oral versus depot antipsychotic drugs. Until well conducted and reported randomised trials are undertaken clinicians will be in doubt as to the effects of perphenazine depots and people with schizophrenia should exercise their own judgement or ask to be randomised.