Cerebral D2 and 5-HT2 receptor occupancy in schizophrenic patients treated with olanzapine or clozapine

Rosa Maria Moresco, Roberto Cavallaro, Cristina Messa, Daniele Bravi, Clara Gobbo, Laura Galli, Giovanni Lucignani, Cristina Colombo, Giovanna Rizzo, Isabella Velonà, Enrico Smeraldi, Ferruccio Fazio

Research output: Contribution to journalArticlepeer-review


We report the results of a double-blind, randomized prospective trial on D2 and 5-HT2 receptor occupancy and the clinical effects of olanzapine versus clozapine in a sample of neuroleptic-refractory schizophrenic patients. Receptor occupancy was evaluated in different cortical areas and in basal ganglia using [18F]fluoro-ethyl-spiperone ([ 18F]FESP) and positron emission tomography (PET). A total of 15 neuroleptic-free patients completed the study undergoing a baseline and a post-treatment PET scan (olanzapine, nine patients, one female; clozapine, six patients, three female) 8 weeks after starting treatment. PET data were analysed both by regions of interest and on a voxel-by-voxel basis using Statistical Parametric Mapping (SPM96). Olanzapine and clozapine induced a similar and significant inhibition of [18F]FESP binding index in the cortex. In the basal ganglia, receptor occupancy was significantly higher with olanzapine than with clozapine (p = 0.0018). By contrast, no differences in receptor occupancy were detected at the level of the pituitary gland. Clinical outcomes, in particular a full extrapyramidal tolerability, were similar. In this sample of neuroleptic-refractory schizophrenic patients, olanzapine and clozapine showed a different pattern of occupancy of D2-like receptor despite a common lack of extrapyramidal side-effects.

Original languageEnglish
Pages (from-to)355-365
Number of pages11
JournalJournal of Psychopharmacology
Issue number3
Publication statusPublished - Sept 2004


  • Basal ganglia
  • Clozapine
  • Emission tomography
  • Olanzapine
  • Pituitary
  • Receptor occupancy

ASJC Scopus subject areas

  • Pharmacology
  • Psychiatry and Mental health
  • Neuroscience(all)


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