title: Dopamine D2 receptor occupancy by olanzapine or risperidone in young patients with schizophrenia.
abstract: A crucial characteristic of antipsychotic medication is the occupancy of the dopamine (DA) D2 receptor. We assessed striatal DA D2 receptor occupancy by olanzapine and risperidone in 36 young patients [31 males, 5 females; mean age 21.1 years (16-28)] with first episode schizophrenia, using [123I]iodobenzamide (IBZM) SPECT. The occupancy of DA D2 receptors was not significantly different between olanzapine and risperidone. However, in subgroups of most prescribed doses, DA D2 occupancy was higher in the risperidone 4-mg group (79%) compared to the olanzapine 15-mg group (62%). [123I]IBZM binding ratios decreased with olanzapine dose (r = -0.551; P < 0.01), indicating higher DA D2 receptor occupancy with higher olanzapine dose. Akathisia and positive symptoms were correlated with [123I]IBZM binding ratio (r = -0.442; P < 0.01; and r = -0.360; P < 0.05, respectively). Prolactin (PRL) levels were elevated in the risperidone, but not in the olanzapine group, at comparable D2 receptor occupancy levels. In the olanzapine group, PRL levels were correlated with [123I]IBZM binding ratio (r = -0.551; P < 0.01). In conclusion, both olanzapine and risperidone induce a high striatal D2 receptor occupancy, dependent on dose and group formation. The lower incidence of prolactin elevation with olanzapine, compared to risperidone, may not be attributed to a lower D2 receptor occupancy.
authors.affiliation: Department of Psychiatry, Academic Medical Centre, Amsterdam, The Netherlands. j.lavalaye@amc.uva.nl
authors.forename: J
authors.initials: J
authors.lastname: Lavalaye
authors.forename: D H
authors.initials: DH
authors.lastname: Linszen
authors.forename: J
authors.initials: J
authors.lastname: Booij
authors.forename: L
authors.initials: L
authors.lastname: Reneman
authors.forename: B P
authors.initials: BP
authors.lastname: Gersons
authors.forename: E A
authors.initials: EA
authors.lastname: van Royen
mesh_terms: D000293:Adolescent; D000328:Adult; D014150:Antipsychotic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D001549:Benzamides; D001569:Benzodiazepines; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects; D001931:Brain Mapping; D003287:Contrast Media; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D000077152:Olanzapine; D010890:Pirenzepine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011569:Psychiatric Status Rating Scales; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2 / Q000187:drug effects* / Q000502:physiology; D018967:Risperidone / Q000009:adverse effects / Q000627:therapeutic use*; D012559:Schizophrenia / Q000000981:diagnostic imaging / Q000188:drug therapy*; D015899:Tomography, Emission-Computed, Single-Photon; D016896:Treatment Outcome
chemical_list: D014150:Antipsychotic Agents; D001549:Benzamides; D003287:Contrast Media; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; D001569:Benzodiazepines; D010890:Pirenzepine; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide; D018967:Risperidone; D000077152:Olanzapine