Objectives: Narrative, unsystematic reviews revealed no differences in efficacy between the various first-generation antipsychotics (FGAs) resulting in the psychopharmacological assumption of comparable efficacy between the different FGAs. We sought to determine if the assumption of comparable efficacy of all FGAs can be regarded as evidence-based using meta-analytic statistics.
Methods: A systematic literature survey (Cochrane Schizophrenia Group trial register) was applied to identify all RCTs that compared oral haloperidol with another oral FGA in schizophrenia. Primary outcome was dichotomous treatment response. Secondary outcomes were symptom severity measured by rating scales, discontinuation rates, and specific adverse effects.
Results: Altogether, 79 RCTs with 4343 participants published between 1962 and 1999 were included. We found a significant between-group difference only between haloperidol and nemonapride, but not for the remaining 19 investigated FGAs. There were no significant differences for discontinuation rates.
Conclusions: As most of the single meta-analytic comparisons can be regarded as underpowered, the evidence for the assumption of comparable efficacy of all FGAs is inconclusive. We therefore cannot confirm or reject the statements of previous narrative, unsystematic reviews in this regard. Our findings were limited by the small sample size in the individual comparisons and the low methodological quality in many included studies.
Keywords: Schizophrenia; antipsychotics; effect sizes; haloperidol; meta-analysis.