Chlorpromazine versus every other antipsychotic for schizophrenia: a systematic review and meta-analysis challenging the dogma of equal efficacy of antipsychotic drugs

It is one of the major psychiatric dogmas that the efficacy of all antipsychotic drugs is same. This statement originated from old, narrative reviews on first-generation antipsychotics, but this old literature has never been meta-analysed. We therefore conducted a meta-analysis of randomised controlled trials on the efficacy of chlorpromazine versus any other antipsychotic in the treatment of schizophrenia. If the benchmark drug chlorpromazine were significantly more or less effective than other antipsychotics, the notion of equal efficacy would have to be rejected. We searched the Cochrane Schizophrenia Group׳s specialized register, MEDLINE, EMBASE, PsychInfo and reference lists of relevant articles. The primary outcome was response to treatment. We also analyzed mean values of schizophrenia rating scales at endpoint and drop-out rates. 128, mostly small, RCTs with 10667 participants were included. Chlorpromazine was compared with 43 other antipsychotics and was more efficacious than four (butaperazine, mepazine, oxypertine and reserpine) and less efficacious than other four antipsychotics (clomacran, clozapine, olanzapine and zotepine) in the primary outcome. There were no statistically significant efficacy differences between chlorpromazine and the remaining 28 antipsychotics. The most important finding was that, due to low numbers of participants (median 50, range 8-692), most comparisons were underpowered. Thus we infer that the old antipsychotic drug literature was inconclusive and the claim for equal efficacy of antipsychotics was never evidence-based. Recent meta-analyses on second-generation antipsychotics were in a better position to address this question and small, but consistent differences between drugs were found.