Depot perphenazine decanoate and enanthate for schizophrenia

Long acting depot preparations (decanoate and enanthate) of the oral antipsychotics perphenazine are available for people with schizophrenia. Evidence available for their efficacy and safety is limited. This review identifies randomised trials comparing depot perphenazine to other depot antipsychotics and perphenazine decanoate to enanthate.

Authors' conclusions: 

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 four trials with useful data is 313. None of the studies observed the effects 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.

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Antipsychotic 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 antipsychotics and other depot antipsychotic preparations for people with schizophrenia in terms of clinical, social and economic outcomes.

Search strategy: 

We updated previous searches of the Cochrane Schizophrenia Group Register (June 1998), Biological Abstracts (1982-1998), the Cochrane Library (Issue 2, 1998), EMBASE (1980-1998), MEDLINE (1966-1998), and PsycLIT (1974-1998) by searching the Cochrane Schizophrenia Group Register (March 2004). References of all identified trials were also inspected for more studies and industry contacted.

Selection criteria: 

We compared randomised clinical trials focusing on people with schizophrenia where depot perphenazine decanoate and enanthate, oral antipsychotics or other depot preparations.

Data collection and analysis: 

We reliably selected studies, quality rated them and extracted data. For dichotomous data we estimated the Relative Risk (RR) with the 95% confidence intervals (CI). Where possible, we calculated the number needed to treat statistic (NNT). Analysis was by intention-to-treat.

Main results: 

Only four studies (Ahlfors 1980, Eufe 1979, Knudsen 1985c, Tegeler 1979), randomising a total 313 people could be included in this review and this combined with an overall lack of usable data limits any interpretation of results. Perphenazine enanthate was not significantly any better or worse than other depot antipsychotics in most of the main outcomes such as global state, relapse or leaving the study early. We found some differences favouring the control groups for adverse effects.

One study (Ahlfors 1980) of six months' duration (n=172), compared perphenazine enanthate to clopenthixol decanoate. There were no differences between the two groups for outcomes of global improvement, relapse and leaving the study early. More people in the perphenazine enanthate group, however, required anticholinergic drugs than those allocated to clopenthixol decanoate (RR 1.12 CI 1.0 to 1.2, 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 (RR 1.36, CI 1.1 to 1.8 NNT 5) than those allocated the decanoate ester of the same drug and required more anticholinergic drugs (RR 1.47 CI 1.1 to 2.0, NNT 4).