olanzapine and setoperone

There have been conflicting reports as to whether olanzapine produces lower occupancy of striatal dopamine D(2)/D(3) receptor than typical antipsychotic drugs and preferential occupancy of extrastriatal dopamine D(2)/D(3) receptors. We performed [(18)F] fallypride PET studies in six schizophrenic subjects treated with olanzapine and six schizophrenic subjects treated with haloperidol to examine the occupancy of striatal and extrastriatal dopamine receptors by these antipsychotic drugs. [(18)F] setoperone PET studies were performed in seven olanzapine-treated subjects to determine 5-HT(2A) receptor occupancy. Occupancy of dopamine D(2)/D(3) receptors by olanzapine was not significantly different from that seen with haloperidol in the putamen, ventral striatum, medial thalamus, amygdala, or temporal cortex, that is, 67.5-78.2% occupancy; olanzapine produced no preferential occupancy of dopamine D(2)/D(3) receptors in the ventral striatum, medial thalamus, amygdala, or temporal cortex. There was, however, significantly lower occupancy of substantia nigra/VTA dopamine D(2)/D(3) receptors in olanzapine-treated compared to haloperidol-treated subjects, that is, 40.2 vs 59.3% (p=0.0014, corrected for multiple comparisons); in olanzapine-treated subjects, the substantia nigra/VTA was the only region with significantly lower dopamine D(2)/D(3) receptor occupancy than the putamen, that is, 40.2 vs 69.2% (p<0.001, corrected for multiple comparison). Occupancy of 5-HT(2A) receptors was 85-93% in the olanzapine- treated subjects. The results of this study demonstrated that olanzapine does not produce preferential occupancy of extrastriatal dopamine D(2)/D(3) receptors but does spare substantia nigra/VTA receptors. Sparing of substantia nigra/VTA dopamine D(2)/D(3) receptor occupancy may contribute to the low incidence of extrapyramidal side effects in olanzapine-treated patients.

Topics: Adult; Antipsychotic Agents; Benzamides; Benzodiazepines; Brain Chemistry; Corpus Striatum; Dopamine Antagonists; Female; Haloperidol; Humans; Image Processing, Computer-Assisted; Male; Middle Aged; Olanzapine; Positron-Emission Tomography; Pyrimidinones; Pyrrolidines; Radiopharmaceuticals; Receptor, Serotonin, 5-HT2A; Receptors, Dopamine D3; Schizophrenia; Serotonin Antagonists

Olanzapine is a new atypical antipsychotic recently introduced for the treatment of schizophrenia. The purpose of this study was to investigate olanzapine's binding to the serotonin 5-HT2 and dopamine D2 receptors in schizophrenic patients being treated with clinically relevant doses.. Twelve patients with schizophrenia were randomly assigned to 5, 10, 15, or 20 mg/day of olanzapine in a prospective fashion. Three other subjects taking 30-40 mg/day were also included. Once steady-state plasma levels were achieved, dopamine D2 and serotonin 5-HT2 receptors were assessed by using [11C]raclopride and [18F]setoperone positron emission tomography imaging, respectively. Ratings of clinical status, extrapyramidal side effects, and prolactin levels were also obtained.. Olanzapine induced near saturation of the 5-HT2 receptors, even at 5 mg/day. Its D2 occupancy increased with dose: patients taking 5-20 mg/day showed 43%-80% D2 occupancy, while patients taking 30-40 mg/day showed 83%-88%.. Olanzapine is a potent 5-HT2 blocker and shows a higher 5-HT2 than D2 occupancy at all doses. However, its D2 occupancy is higher than that of clozapine and similar to that of risperidone. In the usual clinical dose range of 10-20 mg/day, its occupancy varies from 71% to 80%, and this restricted range may explain its freedom from extrapyramidal side effects and prolactin elevation. However, doses of 30 mg/day and higher are associated with more than 80% D2 occupancy and may have a higher likelihood of prolactin elevation and extrapyramidal side effects.

Topics: Adult; Antipsychotic Agents; Benzodiazepines; Carbon Radioisotopes; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Fluorine Radioisotopes; Humans; Male; Olanzapine; Pirenzepine; Prolactin; Pyrimidinones; Raclopride; Receptors, Dopamine D2; Receptors, Serotonin; Salicylamides; Schizophrenia; Tomography, Emission-Computed; Treatment Outcome

Dopamine D2 receptor occupancy measurements provide a valid predictor of antipsychotic response, extrapyramidal side effects, and elevation of prolactin levels. The new antipsychotics clozapine, risperidone, and olanzapine obtain antipsychotic response with few extrapyramidal side effects and little prolactin elevation. The purpose of this study was to compare the D2 and serotonin 5-HT2 receptor occupancies of these drugs in patients receiving multiple-dose, steady-state regimens.. Forty-four patients with schizophrenia (16 taking risperidone, 2-12 mg/day; 17 taking olanzapine, 5-60 mg/day; and 11 taking clozapine, 75-900 mg/day) had their D2 and 5-HT2 occupancies determined with the use of [11C]raclopride and [18F]setoperone, respectively, and positron emission tomography imaging.. Clozapine showed a much lower D2 occupancy (16%-68%) than risperidone (63%-89%) and olanzapine (43%-89%). Risperidone and olanzapine gave equal D2 occupancies at doses of 5 and 20 mg/day, respectively. All three drugs showed greater 5-HT2 than D2 occupancy at all doses, although the difference was greatest for clozapine.. Clozapine, at doses known to be effective in routine clinical settings, showed a D2 occupancy clearly lower than that of typical antipsychotics, while risperidone and olanzapine at their usual clinical doses gave the same level of D2 occupancy as low-dose typical antipsychotics. The results also suggest that some previous clinical comparisons of antipsychotics may have been confounded by different levels of D2 occupancy. Clinical comparisons of these drugs, matching for D2 occupancy, may provide a better measure of their true "atypicality" and will help in understanding the contribution of non-D2 receptors to antipsychotic effects.

Topics: Adult; Antipsychotic Agents; Benzodiazepines; Carbon Radioisotopes; Clozapine; Drug Administration Schedule; Female; Fluorine Radioisotopes; Humans; Male; Middle Aged; Olanzapine; Pirenzepine; Pyrimidinones; Raclopride; Receptors, Dopamine D2; Receptors, Serotonin; Risperidone; Salicylamides; Schizophrenia; Tomography, Emission-Computed