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Objective. We hypothesized that an excessive dose of antipsychotic drug and/or a larger number of antipsychotic drug worsens cognitive functions in schizophrenia patients. To confirm the hypothesis, we compared several cognitive functions in the patients taking a second-generation antipsychotic drug (SGA) only (SGA monotherapy group) with those in patients taking more than two kinds of antipsychotic drugs (polypharmacy group). Methods. The cognitive functions of 136 chronic schizophrenia patients were evaluated using the Brief Assessment of Cognition in Schizophrenia, Japanese-language version (BACS-J). Results. A significantly negative correlation was found between the composite score in the BACS-J and the chlorpromazine equivalence of doses of antipsychotic drugs in whole patients ( r = -0.43, P < 0.001). Schizophrenia patients in the polypharmacy group had lower composite scores than those in the SGA monotherapy group in the BACS-J. No difference was observed in the composite score and the primary score in each item in the BACS-J between patients with first- plus second-generation antipsychotic drug (FGA + SGA group) and those with two kinds of SGA (SGA + SGA group). Conclusion. These results suggest that an excessive dose of antipsychotic drugs regardless of FGA and SGA might cause the deterioration of cognitive functions in chronic Japanese schizophrenia patients. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the effects of the atypical antipsychotics risperidone, olanzapine, and aripiprazole on the cognitive functions of Japanese patients with schizophrenia with respect to dosage amounts and dosing schedules. We performed a cross-sectional survey using the Brief Assessment of Cognition in Schizophrenia – Japanese Language Version (BACS-J) to evaluate the neurocognitive functions of 101 schizophrenic patients who took the same dose of one of the three aforementioned antipsychotics for at least 3 months. The BACS-J composite score correlated negatively with the prescribed dosages of risperidone and olanzapine. In contrast, we did not find a correlation between the BACS-J composite score and the prescribed dosage of aripiprazole. Moreover, the primary scores for verbal learning, motor function, and attention and processing speed were significantly lower among the patients who were taking the prescribed dosage of risperidone. The scores for verbal learning and motor function were also significantly lower when correlated with the prescribed dosage of olanzapine. We did not find a correlation between any of the primary scores on the BACS-J and the prescribed dosage of aripiprazole. In fact, the results suggest there is no linear relationship between the dose of aripiprazole and cognitive impairment, which may be due to its unique pharmacological profile. [Copyright &y& Elsevier]