clozapine and setoperone

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

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.. 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 [18F]setoperone, a high-affinity radioligand for cortical 5-HT2A receptors.. A dose-dependent decrease in the number of available cortical binding sites for [18F] 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.. 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.

Topics: Adolescent; Adult; Amisulpride; Animals; Antipsychotic Agents; Cerebral Cortex; Chlorpromazine; Clozapine; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Fluorine Radioisotopes; Humans; Male; Pyrimidinones; Receptor, Serotonin, 5-HT2A; Receptors, Serotonin; Schizophrenia; Sulpiride; Tomography, Emission-Computed

In vivo occupancy by typical or atypical antipsychotic drugs of dopamine D-1, D-2 and serotonin (5-HT)2 receptors in the membranes and slices of the rat brain was measured using N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), an irreversible antagonist at these receptor sites. In the membranes, the occupancy of D-1 receptors in the striatum by all tested drugs except cis-flupenthixol was minimal. Typical antipsychotic drugs such as chlorpromazine (10 mg/kg), haloperidol (1 mg/kg), cis-flupenthixol (1 mg/kg) and zotepine (5 mg/kg) occupied predominantly D-2 receptors in the striatum. Among atypical antipsychotic drugs, sulpiride (30 mg/kg) and amperozide (1 mg/kg) had no effect on the EEDQ-induced reduction in D-1, D-2 or 5-HT2 receptors, whereas clozapine (10 mg/kg), fluperlapine (10 mg/kg), risperidone (1 mg/kg), setoperone (0.25 mg/kg) and ORG 5222 (0.25 mg/kg) occupied mainly 5-HT2 receptors in the frontal cortex. In the slices, the occupancy by all tested drugs of D-1 receptors in the striatum, nucleus accumbens and substantia nigra was minimal with the exception of clozapine which showed about 30% occupancy in the substantia nigra. Typical antipsychotic drugs, chlorpomazine (10 mg/kg) and haloperidol (1 mg/kg) occupied predominantly D-2 receptors in the striatum and the nucleus accumbens. On the other hand, atypical antipsychotic drugs, clozapine (10 mg/kg) and risperidone (1 mg/kg), occupied mainly 5-HT2 receptors in the frontal cortex. These results suggest that there is a certain group of atypical antipsychotic drugs characterized by high occupancy of 5-HT2 receptors and low or minimum occupancy of D-2 receptors. These characteristics may be relevant to their weak potency in producing extrapyramidal side effects in man or catalepsy in rodents. Although we could find no clear regional differences in receptor occupancies by these antipsychotic drugs, further study are needed to elucidate this issue.

Topics: Animals; Antipsychotic Agents; Autoradiography; Brain; Chlorpromazine; Clozapine; Dibenzothiepins; Flupenthixol; Haloperidol; In Vitro Techniques; Isoxazoles; Male; Piperidines; Pyrimidinones; Rats; Rats, Wistar; Receptors, Dopamine; Receptors, Serotonin; Risperidone

The effect of acute treatment with seven atypical antipsychotic drugs and four typical antipsychotic drugs on serotonin2 (5-HT2) receptor binding sites in rat cerebral cortex was studied. Among the atypical antipsychotic drugs examined, clozapine, fluperlapine, RMI-81582 and setoperone decreased the density of 5-HT2 receptors, but ticspirone, amperozide and melperone did not. None of the drugs affected the Kd value. Among the typical antipsychotic drugs, loxapine decreased Bmax and increased the Kd of 5-HT2 receptor binding sites, whereas chlorpromazine and cis-flupenthixol had no effect. Clothiapine, a typical antipsychotic drug of the same chemical class as clozapine, decreased Bmax without increasing Kd. The downregulation of 5-HT2 receptor binding sites following a single injection of clozapine, 20 mg/kg, remained almost unchanged during the first 72 hrs and was still significantly decreased for up to 120 hrs. There was no relationship between the affinity for the downregulation of rat cortical 5-HT2 receptor binding site and 5-HT2 receptor density. Coadministration of the D1 dopamine agonist, SKF-38393, did not affect the clozapine-induced downregulation. It is suggested that rapid and prolonged downregulation of 5-HT2 receptor sites is characteristic of some but not all atypical antipsychotic drugs and is not specific to atypical antipsychotic drugs. Dibenzo-epines (clozapine, loxapine, amoxapine, chlothiapine) consistently downregulate 5-HT2 receptors in frontal cortex after acute treatment.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Antipsychotic Agents; Butyrophenones; Cerebral Cortex; Chlorpromazine; Clozapine; Dibenzazepines; Dibenzothiazepines; Down-Regulation; Flupenthixol; Kinetics; Loxapine; Male; Pyrimidinones; Rats; Rats, Inbred Strains; Receptors, Serotonin; Spiro Compounds; Time Factors

The ability of atypical and typical antipsychotics to antagonize serotonin (5-HT) receptor-mediated temperature and neuroendocrine responses was tested in rats. Clozapine, melperone and setoperone, three atypical neuroleptics, blocked in a dose-dependent manner, the hyperthermic response to the 5-HT agonist, MK-212, whereas chlorpromazine and haloperidol were ineffective. The hypothermic response to the 5-HT1A agonist, 8-OH-DPAT, was unaltered by any of the atypical neuroleptics tested. Similarly, MK-212-induced corticosterone secretion was blocked in a dose-related manner by clozapine, melperone and setoperone but was relatively unaffected by either haloperidol or chlorpromazine. The increase in corticosterone secretion observed following 8-OH-DPAT administration was not attenuated by pretreatment with the atypical or typical antipsychotics tested. These data indicate that atypical neuroleptics are effective 5-HT2 but not 5-HT1A antagonists in vivo. Conversely, the typical neuroleptics, haloperidol and chlorpromazine do not block the 5-HT receptors involved in activation of the hypothalamic-pituitary-adrenal axis or thermoregulation.

Topics: 8-Hydroxy-2-(di-n-propylamino)tetralin; Animals; Antipsychotic Agents; Body Temperature; Butyrophenones; Chlorpromazine; Clozapine; Corticosterone; Haloperidol; Male; Neurosecretory Systems; Pyrazines; Pyrimidinones; Rats; Rats, Inbred Strains; Receptors, Serotonin; Serotonin Antagonists; Tetrahydronaphthalenes