Clozapine, but not typical antipsychotics, correct P50 suppression deficit in patients with schizophrenia

Objective: To find out if there is a difference in P50 suppression between patients using typical antipsychotic drugs and those using clozapine, as well as to confirm the findings of abnormal P50 suppression in patients with schizophrenia, when compared to healthy volunteers. Methods: Fifty patients with schizophrenia and 25 healthy volunteers were divided into 3 groups: group 1 - patients using typical antipsychotics; group 2 - patients using clozapine; group 3 - controls. Before the examination, all patients were interviewed by a psychiatrist using the Brief Psychiatry Rating Scale (BPRS). Results: The average S2/S1 ratio was 0.82 +/- 0.45 in group 1, 0.57 +/- 0.41 in group 2, and 0.44 +/- 0.27 in group 3 (P = 0.003). Statistical analysis showed a significant difference when the results of group 1 were compared to those of groups 2 (P = 0.045) and 3 (P = 0.001). There was no significant difference between groups 2 and 3 (P = 0.182). There was a significant difference in the S1 - S2 difference only between groups 1 and 3 (P = 0.007), but a non-significant trend towards a similar difference was found between groups I and 2 (P = 0.067). There was no correlation between the BPRS values and any P50 parameter. Conclusions: The suppression of P50 among patients using clozapine was significantly greater than that obtained in patients using typical antipsychotics. Significance: This study confirms, in a more evident way, the improvement of the suppression of P50 potential in schizophrenics using clozapine. Additionally, it discusses the physiopathological mechanism involved. (C) 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.