Perphenazine versus low-potency first-generation antipsychotic drugs for schizophrenia

Antipsychotic drugs are the core treatment for schizophrenia. Treatment guidelines state that there is no difference in efficacy between the various first-generation antipsychotics, however, low-potency first-generation antipsychotic drugs are sometimes perceived as less efficacious than high-potency first-generation compounds by clinicians, and they also seem to differ in their side effects.

To review the effects of high-potency, first-generation perphenazine compared with low-potency, first-generation antipsychotic drugs for people with schizophrenia.

We searched the Cochrane Schizophrenia Group Trials Register (October 2010).

We included all randomised controlled trials (RCTs) comparing perphenazine with first-generation, low-potency antipsychotic drugs for people with schizophrenia or schizophrenia-like psychoses.

We extracted data independently. For dichotomous data we calculated risk ratios (RR) and their 95% confidence intervals (CI) on an intention-to-treat basis and using a random-effects model.

The review currently includes four relevant randomised trials with 365 participants. The size of the included studies was between 42 and 158 participants with a study length between one and four months. Overall, the methods of sequence generation and allocation concealment were poorly reported. Most studies were rated as low risk of bias in terms of blinding. Overall, attrition bias in the studies was high.The effects of perphenazine and low-potency antipsychotic drugs seemed to be similar in terms of the primary outcome - response to treatment (perphenazine 58%, low-potency antipsychotics 59%, 2 RCTs, n = 138, RR 0.97 CI 0.74 to 1.26 - moderate quality of evidence). There was also no clear evidence of a difference in acceptability of treatment with the number of participants leaving the studies early due to any reason, however results were imprecise (perphenazine 30%, low-potency antipsychotics 28%, 3 RCTs, n = 323, RR 0.78 CI 0.35 to 1.76, very low quality of evidence).There were low numbers of studies available for the outcomes experiencing at least one adverse effect (perphenazine 33%, low-potency antipsychotics 47%, 2 RCTs, n = 165, RR 0.83 CI 0.36 to 1.95, low quality evidence) and experiencing at least one movement disorder (perphenazine 22%, low-potency first-generation antipsychotics 0%, 1 RCT, n = 69, RR 15.62 CI 0.94 to 260.49, low quality evidence), and the confidence intervals for the estimated effects did not exclude important differences. Akathisia was more frequent in the perphenazine group (perphenazine 25%, low-potency antipsychotics 22%, 2 RCTs, n = 227, RR 9.45 CI 1.69 to 52.88), whereas severe toxicity was less so (perphenazine 42%, low-potency antipsychotics 69%, 1 RCT, n = 96, RR 0.61 CI 0.41 to 0.89).There were three deaths in the low-potency group by four months but the difference between groups was not significant (perphenazine 0%, low-potency antipsychotics 2%, 1 RCT, n = 96, RR 0.14 CI 0.01 to 2.69, moderate quality evidence). No data were available for our prespecified outcomes of interest sedation or quality of life. Data were not available for other outcomes such as relapse, service use, costs and satisfaction with care.The event rates reported quote simple aggregates and are not based on the RRs.

The results do not show a superiority in efficacy of high-potency perphenazine compared with low-potency first-generation antipsychotics. There is some evidence that perphenazine is more likely to cause akathisia and less likely to cause severe toxicity, but most adverse effect results were equivocal. The number of studies as well as the quality of studies is low, with quality of evidence for the main outcomes ranging from moderate to very low, so more randomised evidence would be needed for conclusions to be made.