Binding of Antipsychotic Drugs to Cortical 5-HT: A PET Study of Chlorpromazine, Clozapine, and Amisulpride in Schizophrenic Patients2A: A PET Study of Chlorpromazine, Clozapine, and Amisulpride in Schizophrenic Patients Receptors: A PET Study of Chlorpromazine, Clozapine, and Amisulpride in Schizophrenic Patients

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Abstract

Objective

This study examined the binding to cortical serotonin 5-HT2A receptors of conventional doses of the typical neuroleptic chlorpromazine in comparison with clozapine, the prototype atypical antipsychotic, and amisulpride, a specific dopamine D2-D3 blocker.

Method

Seventeen schizophrenic patients treated with chlorpromazine (75-700 mg/day), four treated with clozapine (200-600 mg/day), and five treated with amisulpride (200-1200 mg/day) were studied. Cortical 5-HT2A binding was estimated by reference to the values for 14 antipsychotic-free schizophrenic subjects with the use of positron emission tomography and [(18) F]setoperone, a high-affinity radioligand for cortical 5-HT2A receptors.

Results

A dose-dependent decrease in the number of available cortical binding sites for [(18) F]setoperone was demonstrated in the chlorpromazine group; for the highest dose, there was a virtual lack of sites available for binding. A very low percentage of available binding sites was also observed in the clozapine-treated patients at all doses. This suggests a high level of 5-HT2A blockade with both clozapine and high doses of chlorpromazine. No significant binding of amisulpride to 5-HT2A receptors was detected.

Conclusions

A high level of 5-HT2A receptor blockade does not appear specific to clozapine in comparison with high doses of chlorpromazine, suggesting that the distinct clinical profiles of both drugs are unrelated to 5-HT2A blockade itself.

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