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.