Comparison of the effects of risperidone and haloperidol on regional cerebral blood flow in schizophrenia

Background: Atypical antipsychotics, such as risperidone, have been shown t o be more effective for the treatment of the symptoms of schizophrenia and have a greater beneficial effect on neurocognition compared to the conventi onal antipsychotics. The present study used [O-15]H2O positron emission tom ography imaging of regional cerebral blood flow to examine and compare the effects of haloperidol and risperidone on brain function. Methods: Thirty-two subjects with schizophrenia participated in the study. Each subject was scanned in a medication-free state, and after being on a s table clinically assigned dose of either risperidone or haloperidol for 3 w eeks. The off-medication scan was subtracted from the on-medication scan. u sing a,within-subjects design. A randomization analysis was used to determi ne differences between the effects of haloperidol and risperidone on region al cerebral blood flow. Results: Haloperidol was associated with a significantly greater increase i n regional cerebral blood flow in the left putamen and posterior cingulate, and a significantly greater decrease in regional cerebral blood flow in fr ontal regions compared to risperidone. Risperidone was associated with a si gnificantly greater decrease in regional cerebral blood flow in the cerebel lum bilaterally compared to haloperidol. Conclusions: The results show that risperidone and haloperidol have signifi cantly different effects on brain function, which may be related to their d ifferences in efficacy and side effects. Further work is required to more p recisely determine the mechanisms by which different antipsychotic medicati ons exert their therapeutic effects on the clinical symptoms and cognition in schizophrenia. These findings emphasize the importance of controlling fo r both medication status and the individual antipsychotic in neuroimaging s tudies. Biol Psychiatry (C) 2001 Society of Biological Psychiatry.