Several prescription patterns of antipsychotic drugs influence cognitive functions in Japanese chronic schizophrenia patients.

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.