Does sigma receptor antagonism predict clinical antipsychotic efficacy?

The psychotogenic actions of sigma receptor agonists, such as pentazocine, have led to the hypothesis that sigma receptor antagonists may be putative antipsychotic agents. In this study, BW234U, a selective but relatively weak sigma receptor antagonist was compared at two different dosage ranges with chlorpromazine and placebo in a double-blind randomized treatment trial in schizophrenic patients undergoing acute exacerbation. During the 4-week blinded treatment period, there was a modest drop in Brief Psychiatric Rating Scale (BPRS) score in the chlorpromazine group, however, neither dosage range of BW234U, nor placebo produced a significant drop in the BPRS. Our results suggest that BW234U is an ineffective anti-psychotic agent in schizophrenics experiencing acute exacerbation of their illness. Due to BW234U's relatively weak antagonism at the sigma recognition site, this does not rule out the possibility that more potent and equally selective sigma antagonists may possess antipsychotic efficacy.