Dropout rates in randomised antipsychotic drug trials

Rationale: It has been assumed that new atypical drugs improve treatment co mpliance due to fewer adverse effects. Data supporting this assumption are scarce. Objectives: The aim of this study was to study attrition rates in r andomised controlled trials of oral administration of conventional antipsyc hotic drugs, atypical antipsychotic drugs and placebo. Methods: The databas e of the Schizophrenia Module of the Cochrane Library was utilised for the present study. The data in the Cochrane Module are collected by identifying relevant randomised controlled trials from several electronic databases an d other sources. Number of dropouts was defined as patients leaving the stu dy preterm due to any reason. Results: Data from 328 treatment groups, cons isting of 18,585 randomised subjects from 163 drug trials, were entered in the analysis. One-third of the subjects had dropped out of the trials. The dropout rates significantly increased for each calendar year. Year of trial publication, type of drug and trial length remained statistically signific ant contributors to dropout rates. In a model incorporating year of publica tion and trial length, placebo groups and groups treated with conventional antipsychotics had significantly higher attrition rates than groups treated with atypical drugs. When clozapine-treated groups were excluded from the analysis, no statistically significant advantage for atypical drugs over co nventional drugs remained. Conclusions: Trial data implicate that a better compliance can be achieved by favouring atypical drugs rather than conventi onal alternatives in the treatment of schizophrenia. However, this effect i s found only when groups treated with the atypical antipsychotic clozapine are included in the analysis. Our study did not find evidence for a statist ically significant superiority in acceptability of novel atypical drugs whe n compared to conventional antipsychotics.