What do large scale studies of medication in schizophrenia add to our management strategies?

INTRODUCTION: A number of large naturalistic trials have reported in recent years comparing second generation antipsychotic drugs with their predecessors. The conclusions they draw have rightly sparked much debate, but are these studies truly comparable? If not, which of them are most methodologically robust and are these the studies most suitable as a foundation for clinical care guidelines with a strong evidence base. We aimed to conduct a review of the current literature to establish the appropriateness of several recent major clinical studies being used as the basis for clinical guidelines.
METHOD: A literature search using the PUBMED database was carried out. Five major studies comparing antipsychotic efficacy were selected as possible candidates and subjected to further analysis. The studies were: * CUTLASS (Cost Utility of the Latest Antipsychotic Drugs in Schizophrenia study); * CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness study); * SOHO (Schizophrenia outpatients Health Outcomes study); * CAFE (Comparison of Atypicals in First Episode study); * EUFEST (European First Episode Schizophrenia Trial). DISCUSSION: The trials: * CAFE - the trial, although well randomised and blinded, uses discontinuation as a primary endpoint - this is hard to draw conclusions from: patients may discontinue due to side effects, due to lack of efficacy or with against medical advice for a multitude of reasons. As a secondary endpoint, the study does make use of a PANSS scoring system to measure efficacy, adding some weight to the conclusion that olanzapine, quetiaine and risperidone in early psychosis patients have equivalent efficacies. * CATIE - This trial was a comparative study, and so lacked a control arm and used discontinuation of medication an inverse measure of efficacy - an easily quantifiable event, but making for difficult interpretation. However most criticism has been directed at the unusually low (quitiapine, ziprasidone) and high (olanzapine and perphenazine) doses of drug used, which were reflected in their differing rates of efficacy. * CUtLASS This trial allows for less generalisation of its findings to the general population as it makes use a specific sub-population (those switching from one medication to another after a period of treatment). Also some patients were prescribed oral medications and some depot injections - making comparisons difficult due to possible differences in compliance. * EUFEST This trial makes use of discontinuation as an endpoint with the weaknesses we have described. Treatment of first episodes of psychosis is shown to be feasible, but it could not suggest if haloperidol or second generation drugs may be more efficacious. * SOHO - This trial hindered by the observational design of the study and small numbers reaching the primary end point (4%) caution should be exercised in the conclusion that olanzapine is superior to risperidone, quetiapine or typical antipsychotics.
CONCLUSION: There is much information useful for clinical practice to be gathered from the results of these major studies, however, interpretation is hampered by both variations and weakness in study design. On balance it does appear that different antipsychotics possess differing efficacy, but also of relevance to the development of sound clinical guidelines is their differing side effects profile.