olanzapine and zotepine

Clozapine is an atypical antipsychotic demonstrated to be superior in the treatment of refractory schizophrenia which causes fewer movement disorders. Clozapine, however, entails a significant risk of serious blood disorders such as agranulocytosis which could be potentially fatal. Currently there are a number of newer antipsychotics which have been developed with the purpose to find both a better tolerability profile and a superior effectiveness.. To compare the clinical effects of clozapine with other atypical antipsychotics (such as amisulpride, aripiprazole, olanzapine, quetiapine, risperidone, sertindole, ziprasidone and zotepine) in the treatment of schizophrenia and schizophrenia-like psychoses.. We searched the Cochrane Schizophrenia Groups Register (June 2007) and reference lists of all included randomised controlled trials. We also manually searched appropriate journals and conference proceedings relating to clozapine combination strategies and contacted relevant pharmaceutical companies.. All relevant randomised, at least single-blind trials, comparing clozapine with other atypical antipsychotics, any dose and oral formulations, for people with schizophrenia or related disorders.. We selected trials and extracted data independently. For dichotomous data we calculated relative risks (RR) and their 95% confidence intervals (CI) based on a random-effects model. We calculated numbers needed to treat/harm (NNT/NNH) where appropriate. For continuous data, we calculated mean differences (MD) again based on a random-effects model.. The review currently includes 27 blinded randomised controlled trials, which involved 3099 participants. Twelve randomised control trials compared clozapine with olanzapine, five with quetiapine, nine with risperidone, one with ziprasidone and two with zotepine. Attrition from these studies was high (overall 30.1%), leaving the interpretation of results problematic. Clozapine had a higher attrition rate due to adverse effects than olanzapine (9 RCTs, n=1674, RR 1.60 CI 1.07 to 2.40, NNT 25 CI 15 to 73) and risperidone (6 RCTs, n=627, RR 1.88 CI 1.11 to 3.21, NNT 16 CI 9 to 59). Fewer participants in the clozapine groups left the trials early due to inefficacy than risperidone (6 RCTs, n=627, RR 0.40 CI 0.23 to 0.70, NNT 11 CI 7 to 21), suggesting a certain higher efficacy of clozapine.Clozapine was more efficacious than zotepine in improving the participants general mental state (BPRS total score: 1 RCT, n=59, MD -6.00 CI -9.83 to -2.17), but not consistently more than olanzapine, quetiapine, risperidone and ziprasidone. There was no significant difference between clozapine and olanzapine or risperidone in terms of positive or negative symptoms of schizophrenia. According to two studies from China quetiapine was more efficacious for negative symptoms than clozapine (2 RCTs, n=142, MD 2.23 CI 0.99 to 3.48).Clozapine produced somewhat fewer extrapyramidal side-effects than risperidone (use of antiparkinson medication: 6 RCTs, n=304, RR 0.39 CI 0.22 to 0.68, NNT 7 CI 5 to 18) and zotepine (n=59, RR 0.05 CI 0.00 to 0.86, NNT 3 CI 2 to 5). More participants in the clozapine group showed decreased white blood cells than those taking olanzapine, more hypersalivation and sedation than those on olanzapine, risperidone and quetiapine and more seizures than people on olanzapine and risperidone. Also clozapine produced an important weight gain not seen with risperidone.Other differences in adverse effects were less documented and should be replicated, for example, clozapine did not alter prolactin levels whereas olanzapine, risperidone and zotepine did; compared with quetiapine, clozapine produced a higher incidence of electrocardiogram (ECG) alterations; and compared with quetiapine and risperidone clozapine produced a higher increase of triglyceride levels. Other findings that should be replicated were: clozapine improved social functioning less than risperidone and fewer participants in the clozapine group had to be hospitalised to avoid suicide attempts compared. Clozapine may be a little more efficacious than zotepine and risperidone but further trials are required to confirm this finding. Clozapine differs more clearly in adverse effects from other second generation antipsychotics and the side-effect profile could be key in the selection of treatment depending on the clinical situation and a patient's preferences. Data on other important outcomes such as cognitive functioning, quality of life, death or service use are currently largely missing, making further large and well-designed trials necessary. It is also important to take into account that the large number of people leaving the studies early limits the validity and interpretation of our findings.

Topics: Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiazepines; Dibenzothiepins; Humans; Olanzapine; Piperazines; Quetiapine Fumarate; Randomized Controlled Trials as Topic; Risperidone; Schizophrenia; Thiazoles

Topics: Amisulpride; Antipsychotic Agents; Benzodiazepines; Chlorpromazine; Clozapine; Cognitive Behavioral Therapy; Dibenzothiepins; Haloperidol; Humans; Olanzapine; Patient Compliance; Perazine; Pimozide; Risperidone; Schizophrenia; Sulpiride

"Atypical" antipsychotics represent a new generation of antipsychotics with a significantly lower incidence of extrapyramidal side effects (EPS), as well as little or no effect on prolactin elevation. These advantages constitute a major improvement in the treatment of patients with schizophrenia. The exact mechanisms that make these drugs atypical is not clear. However, a preferential action on serotonin 5-HT2 or D4 receptors, or a more rapid dissociation from the dopamine D2 receptor, may account for atypicality. Although the atypical antipsychotics have overcome EPS, other side effects such as weight gain and impaired glucose tolerance/lipid abnormalities have come to the fore. Thus, the challenges are far from over. The current atypicals are much more effective against the psychosis of schizophrenia than against the other, more enduring aspects of this disorder, e.g. negative symptoms and cognitive dysfunction. At present, the atypicals use a "pharmacological shotgun" strategy to treat aspects of the disease in all patients. A more sophisticated and perhaps effective approach to schizophrenia may lie in independently targeting the pathophysiological mechanisms of each clinical dimension (i.e. positive, negative, cognitive, and affective) with more selective drugs that can be combined and individually titrated to the needs of each patient.

Topics: Amisulpride; Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiazepines; Dibenzothiepins; Dopamine Antagonists; Drug Monitoring; Haloperidol; Humans; Imidazoles; Indoles; Olanzapine; Piperazines; Pirenzepine; Quetiapine Fumarate; Receptors, Dopamine D2; Receptors, Dopamine D4; Risperidone; Schizophrenia; Schizophrenic Psychology; Serotonin Antagonists; Sulpiride; Thiazoles; Treatment Outcome

The results of controlled studies of the efficacy of the new atypical neuroleptics in treating negative symptoms show that these antipsychotics have a more pronounced effect on negative symptoms in acute schizophrenic patients than the classical neuroleptics. Supplementary complex statistical analyses substantiate that the increased efficacy of the atypical neuroleptics in treating negative symptoms can only partially be explained by indirect effects of better extrapyramidal tolerability, better effects on productive psychotic symptoms, etc. Instead, it is due largely to the stronger direct effect of these atypical neuroleptics. Clinical studies to evaluate their efficacy in chronic schizophrenic patients with stable, predominantly negative symptoms are still mostly lacking. First results support the presumption that atypical neuroleptics have a direct effect. Parallel to the evaluation of the new atypical neuroleptics, important progress has been made in the methodology of clinical studies in this area.

Topics: Amisulpride; Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiazepines; Dibenzothiepins; Double-Blind Method; Dyskinesia, Drug-Induced; Humans; Imidazoles; Indoles; Neurotransmitter Agents; Olanzapine; Piperazines; Pirenzepine; Quetiapine Fumarate; Randomized Controlled Trials as Topic; Risperidone; Schizophrenia; Schizophrenic Psychology; Sulpiride; Thiazoles

To review systematically data relating to weight changes with atypical antipsychotics.. We conducted a Medline search on October 29 1999 and covered the period 1980-99. All recovered papers were examined for further relevant reports. In addition, we wrote to pharmaceutical manufacturers and 10 practising clinicians to ask them to provide other relevant reports known to them.. Eighty reports mentioning change in body weight were retrieved. Data relating to weight changes were of variable quality. Weight changes were indicated by a variety of measures. The majority of reports related to short-term changes.. All atypical drugs, with the exception of ziprasidone, have been associated with weight increases. Clozapine seems to have the highest risk of weight gain, followed by olanzapine and quetiapine. There is probably a lower risk with risperidone, sertindole and zotepine and a still lower risk with amisulpride. Ziprasidone appears not to be associated with weight gain. In the absence of more compelling data, these rankings must be considered approximate and preliminary. Longer, more robust trials are needed.

Topics: Amisulpride; Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiazepines; Dibenzothiepins; Humans; Imidazoles; Indoles; Olanzapine; Piperazines; Pirenzepine; Quetiapine Fumarate; Risperidone; Sulpiride; Thiazoles; Weight Gain

The introduction of conventional antipsychotics revolutionized the management of psychotic disorders in the 1950s. The use of these agents has been marked by several shortcomings, including their association with severe motor disturbances and their limited efficacy in treating the negative and cognitive symptoms of schizophrenia. Patients noncompliance has largely been the result of subjectively distressing extrapyramidal motor side-effects (EPMS). It was therefore necessary to develop antipsychotic drugs with selective pharmacological profiles, e.g. limbic selectivity. A defining characteristic of atypical neuroleptics is a higher ratio of serotonin receptor blockade to D2 receptor blockade. Their primary advantage is their superior side-effect profile. The implications of EPMS reduction touch several domains of pathology in schizophrenia such as short- and long-term movement disorders, noncompliance, relapse rate, negative symptoms and cognitive dysfunction. Novel antipsychotics may represent the second pharmacological revolution in the treatment of psychotic disorders. There is, however, still a need for a critical evaluation of the risk-benefit-ratio of differing atypical agents.

Topics: Aged; Amisulpride; Antipsychotic Agents; Benzodiazepines; Clozapine; Controlled Clinical Trials as Topic; Dibenzothiazepines; Dibenzothiepins; Haloperidol; Humans; Imidazoles; Indoles; Multicenter Studies as Topic; Olanzapine; Piperazines; Pirenzepine; Placebos; Quetiapine Fumarate; Risperidone; Schizophrenia; Selective Serotonin Reuptake Inhibitors; Serotonin Antagonists; Sulpiride; Thiazoles

Clinical studies with clozapine have clearly demonstrated its superior efficacy over that of conventional antipsychotics in treatment-resistant schizophrenic patients. In comparative trials with these drugs, considerably more patients respond to treatment with clozapine than to conventional antipsychotic medication. Recently, new antipsychotics, such as olanzapine, quetiapine, risperidone, sertindole, and zotepine, have been introduced, but extensive data on their effects in treatment-resistant patients are not yet available. Published studies have drawn criticism in terms of inappropriate titration schedules, nonequivalent dosing between treatment groups, short treatment duration, and inadequate sample sizes. Further research will be needed to determine whether novel antipsychotics may substitute for clozapine in the future or whether clozapine will retain its unique role in the management of patients suffering from difficult-to-treat schizophrenic disorders.

Topics: Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiazepines; Dibenzothiepins; Double-Blind Method; Drug Resistance; Humans; Olanzapine; Pirenzepine; Placebos; Psychotic Disorders; Quetiapine Fumarate; Randomized Controlled Trials as Topic; Schizophrenia; Schizophrenic Psychology; Treatment Outcome

The main objective was to evaluate the effect of five second-generation antipsychotics (amisulpride, quetiapine, olanzapine, risperidone, and zotepine) on prolactinaemia during 6 week therapy in 433 female in-patients with mainly schizophrenic disorders. Secondary objectives included identification of dynamics of change in serum prolactin levels and correlations of changes of prolactinaemia with some demographic and clinical parameters.. The trial was a prospective, open-label, single-center one with a flexible dosing of SGAs. The therapeutic effect of SGAs was assessed by a change of scores of CGI-S and CGI-I scales from a baseline to the endpoint. Blood samples were taken in the morning under fasting condition.. Amisulpride and risperidone increased prolactinaemia significantly in 100% of patients, as early as after week 1 of the therapy. Quetiapine and zotepine relatively reduced prolactinaemia significantly, as early as from week 1 of the quetiapine treatment. Olanzapine led to a transient mild prolactin elevation. The much lower prevalence of hyperprolactinaemia over 2 000 mIU/l differentiates olanzapine from amisulpride and risperidone. Prolactin elevation did not correlate with age, menopausal condition, therapeutic efficacy, antipsychotic daily dose, serum levels of lipids and glucose. There was significant correlation with first vs. subsequent psychotic episodes, weight, EPS and serum levels of thyroid hormones.. Amisulpride and risperidone had marked and early prolactin elevating effects, requiring, therefore, more frequent monitoring of prolactinaemia and associated undesirable effects and risks than olanzapine, quetiapine and zotepine.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Amisulpride; Antipsychotic Agents; Benzodiazepines; Dibenzothiazepines; Dibenzothiepins; Female; Humans; Hyperprolactinemia; Middle Aged; Olanzapine; Prolactin; Prospective Studies; Quetiapine Fumarate; Risperidone; Schizophrenia; Statistics, Nonparametric; Sulpiride

The clinical applications of antipsychotics for symptoms unrelated to schizophrenia, such as behavioral and psychological symptoms, in patients with Alzheimer's disease, and the likelihood of doctors prescribing antipsychotics for elderly people are increasing. In elderly people, drug-induced and aging-associated urinary disorders are likely to occur. The most significant factor causing drug-induced urinary disorders is a decrease in urinary bladder smooth muscle (UBSM) contraction induced by the anticholinergic action of therapeutics. However, the anticholinergic action-associated inhibitory effects of antipsychotics on UBSM contraction have not been sufficiently assessed. In this study, we examined 26 clinically available antipsychotics to determine the extent to which they inhibit acetylcholine (ACh)-induced contraction in rat UBSM to predict the drugs that should not be used by elderly people to avoid urinary disorders. Of the 26 antipsychotics, six (chlorpromazine, levomepromazine (phenothiazines), zotepine (a thiepine), olanzapine, quetiapine, clozapine (multi-acting receptor targeted antipsychotics (MARTAs))) competitively inhibited ACh-induced contractions at concentrations corresponding to clinically significant doses. Further, 11 antipsychotics (perphenazine, fluphenazine, prochlorperazine (phenothiazines), haloperidol, bromperidol, timiperone, spiperone (butyrophenones), pimozide (a diphenylbutylpiperidine), perospirone, blonanserin (serotonin-dopamine antagonists; SDAs), and asenapine (a MARTA)) significantly suppressed ACh-induced contraction; however, suppression occurred at concentrations substantially exceeding clinically achievable blood levels. The remaining nine antipsychotics (pipamperone (a butyrophenone), sulpiride, sultopride, tiapride, nemonapride (benzamides), risperidone, paliperidone (SDAs), aripiprazole, and brexpiprazole (dopamine partial agonists)) did not inhibit ACh-induced contractions at concentrations up to 10

Topics: Acetylcholine; Aging; Animals; Antipsychotic Agents; Chlorpromazine; Cholinergic Antagonists; Clozapine; Dibenzothiepins; Male; Mental Disorders; Methotrimeprazine; Muscle Contraction; Muscle, Smooth; Olanzapine; Quetiapine Fumarate; Rats, Wistar; Urinary Bladder; Urologic Diseases

This study assessed the association between second-generation antipsychotic medications and risk of pneumonia requiring hospitalization in patients with schizophrenia because the evidence is limited in the population. We enrolled a nationwide cohort of 33,024 inpatients with schizophrenia ranged in age from 18 to 65 years, who were derived from the National Health Insurance Research Database in Taiwan from 2000 to 2008. Cases (n = 1741) were defined as patients who developed pneumonia after their first psychiatric admissions. Risk set sampling was used to match each case with 4 controls by age, sex, and the year of the first admission based on nested case-control study. Antipsychotic exposure was categorized by type, duration, and daily dose, and the association between exposure and pneumonia was assessed using conditional logistic regression. We found that current use of clozapine (adjusted risk ratio = 3.18, 95% CI: 2.62-3.86, P < .001) was associated with a dose-dependent increase in the risk. Although quetiapine, olanzapine, zotepine, and risperidone were associated with increased risk, there was no clear dose-dependent relationship. Amisulpride was associated with a low risk of pneumonia. The use of clozapine combined with another drug (olanzapine, quetiapine, zotepine, risperidone, or amisulpride), as assessed separately, was associated with increased risk for pneumonia. In addition, with the exception of amisulpride, each drug was associated with increased risk for pneumonia at the beginning of treatment. Clinicians who prescribe clozapine to patients with schizophrenia should closely monitor them for pneumonia, particularly at the start of therapy and when clozapine is combined with other antipsychotics.

Topics: Adult; Amisulpride; Antipsychotic Agents; Benzodiazepines; Case-Control Studies; Clozapine; Cohort Studies; Dibenzothiazepines; Dibenzothiepins; Drug Therapy, Combination; Female; Humans; Logistic Models; Male; Middle Aged; Olanzapine; Pneumonia; Quetiapine Fumarate; Risk Factors; Risperidone; Schizophrenia; Sulpiride; Taiwan

Dizocilpine (MK-801; 0.3 mg/kg i.p.)-induced disruption in prepulse inhibition of the acoustic startle response (PPI) can be preferentially restored by "atypical" antipsychotics. In contrast, some findings indicate that not all of the "atypical" antipsychotics, such as clozapine and risperidone, are effective in restoring the NMDA antagonist-induced deficits in PPI. In our study, we evaluated the effect of four different "atypical" antipsychotic drugs on deficits in PPI induced by MK-801. Zotepine and risperidone have high affinities to D2-like and 5-HT2A receptors, while clozapine and olanzapine have multipharmacological profiles with the highest affinities to serotonin 5-HT1A,2A/2C receptors and muscarinic receptors. Results have shown that MK-801 disrupted PPI and increased the ASR in rats. Our results showed no effect of zotepine (1 and 2 mg/kg) and risperidone (0.1 and 1 mg/kg) on disrupted PPI by MK-801. Administration of clozapine (5 and 10 mg/kg) and olanzapine (2.5 and 5 mg/kg) restored the deficits in PPI induced by MK-801. Additionally, we found a decrease of approximately 46% in PPI after administration of clozapine (5 mg/kg) and olanzapine (2.5 and 5 mg/kg) without MK-801 treatment. In summary, the four "atypical" antipsychotics had different efficacies to restore the disrupted PPI by MK-801. Only clozapine and olanzapin restored the MK-801-induced deficits in PPI.

Topics: Acoustic Stimulation; Animals; Antipsychotic Agents; Benzodiazepines; Clozapine; Dibenzothiepins; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Male; Olanzapine; Rats; Rats, Wistar; Receptor, Serotonin, 5-HT2A; Receptors, Dopamine D2; Receptors, Muscarinic; Reflex, Startle; Risperidone

Previously, it was demonstrated that the inhibitory effects of atypical antipsychotic drugs such as clozapine and risperidone on noradrenaline transporter (NAT) might in part be associated with their clinical profile. The present study examined the effects of zotepine on NAT in the cells and compared them with those of olanzapine.. Adrenal medullary cells were isolated by a method of collagenase digestion of slices of fresh bovine adrenal medulla and the cells were plated at a density of 4 x 10(6) cells. Cells were incubated with [3H]noradrenaline (NA) in the presence or absence of zotepine or olanzapine. The amount of radioactivity taken into the cells was counted by a liquid scintillation counter. Plasma membranes of bovine adrenal medulla were prepared, and the binding of [3H]desipramine (DMI) was determined by incubating the membrane suspension in binding buffer together with zotepine or olanzapine. Specific binding of [3H] DMI was defined as that binding which was inhibited by nisoxetine.. Both zotepine (10-1000 ng/ml) and olanzapine (10-1000 ng/ml) decreased [3H]NA uptake in a concentration-dependent manner. The IC50 values of zotepine and olanzapine on [3H]NA uptake were 10 +/- 4 and 14 +/- 8 ng/ml, respectively. Eadie-Hofstee analysis of [3H]NA uptake showed that treatment with zotepine and olanzapine decreased the V(max) of uptake without changing the K(m). Both zotepine (10-1000 ng/ml) and olanzapine (30-1000 ng/ml) inhibited [3H]DMI binding in a concentration-dependent manner. The IC50 values of zotepine and olanzapine on [3H]DMI binding were 50 +/- 18, and 120 +/- 38 ng/ml, respectively. Scatchard plot analysis of [3H]DMI binding showed that zotepine and olanzapine decreased the B(max) of binding without altering the K(d).. The inhibitory effects of zotepine and olanzapine might be responsible in part for their clinical profile.

Topics: Adrenal Medulla; Animals; Antidepressive Agents, Tricyclic; Antipsychotic Agents; Benzodiazepines; Cattle; Cell Membrane; Cell Separation; Cells, Cultured; Desipramine; Dibenzothiepins; Kinetics; Norepinephrine; Norepinephrine Plasma Membrane Transport Proteins; Olanzapine

Topics: Analysis of Variance; Antipsychotic Agents; Benzodiazepines; Dibenzothiepins; Hostility; Humans; Olanzapine; Pirenzepine; Risperidone; Schizophrenia; Schizophrenic Psychology

The acute effects of systemic administration of the antipsychotic drug, zotepine, on extracellular dopamine (DA) in the frontal cortex of freely-moving rats were studied using in vivo microdialysis and compared with the actions of clozapine, olanzapine and haloperidol. Treatment with zotepine (1.0 mg/kg, i.p.) resulted in a prolonged elevation of cortical DA levels for up to 180 min post-drug. A maximal rise of +333% was observed at 120 min post-zotepine treatment. Clozapine (10.0 mg/kg, i.p.) also evoked a rise in extracellular DA which was similar in duration (200 min) to that resulting from treatment with zotepine. A maximal rise of +223% was observed at 100 min post-clozapine treatment. Olanzapine (1.0 mg/kg, i.p.) resulted in an immediate increase in DA levels which was maximal 40 min post-treatment (+280%) with levels returning to pre-injection values by 100 min after dosing. In contrast, haloperidol (0.1 mg/kg, i.p.) had no measurable influence on cortical DA levels. Local perfusion with the NA uptake inhibitor, nisoxetine (10 microM), resulted in an increase in cortical DA levels which was maximal at 100 min post-onset of perfusion (+257% above baseline). Administration of zotepine (1.0 mg/kg, i.p.) during nisoxetine perfusion elevated DA levels to a maximum of +301% above baseline, 60 min post-zotepine. These results show that acute administration of each of three drugs with an atypical antipsychotic profile causes an elevation of cortical DA in freely-moving rats at doses relevant to those derived from animal models which predict antipsychotic activity. As a dysfunction in cortical DA is thought to be involved in both the negative symptoms of schizophrenia and cognitive deficits in schizophrenic patients, it is possible that zotepine's ability to elevate cortical DA levels may underlie its effectiveness in successfully treating these components of schizophrenia. Furthermore, the ability of zotepine to elevate cortical DA is more likely to derive from its inhibition of the NA transporter rather than DA receptor blockade in this region.

Topics: Animals; Antipsychotic Agents; Benzodiazepines; Dibenzothiepins; Dopamine; Fluoxetine; Frontal Lobe; Haloperidol; Male; Microdialysis; Olanzapine; Pirenzepine; Rats; Rats, Sprague-Dawley; Receptors, Dopamine; Receptors, Serotonin

Topics: Antipsychotic Agents; Benzodiazepines; Dibenzothiazepines; Dibenzothiepins; Drug Administration Schedule; Humans; Olanzapine; Piperazines; Pirenzepine; Practice Patterns, Physicians'; Quetiapine Fumarate; Risperidone; Schizophrenia; Thiazoles; Treatment Outcome

Topics: Acute Disease; Amisulpride; Antipsychotic Agents; Benzodiazepines; Clozapine; Cost-Benefit Analysis; Dibenzothiazepines; Dibenzothiepins; Dyskinesia, Drug-Induced; Germany; Humans; Neurotransmitter Agents; Olanzapine; Patient Compliance; Pirenzepine; Quetiapine Fumarate; Randomized Controlled Trials as Topic; Risperidone; Schizophrenia; Sulpiride

We determined the affinity and/or potency of two metabolites of clozapine (clozapine-N-oxide and N-desmethylclozapine) and of five atypical neuroleptics, chemically related (olanzapine) or unrelated to clozapine (remoxipride, risperidone, thioridazine, zotepine), at H3 receptors. The specific binding of 3H-N alpha-methylhistamine to rat brain cortex homogenates was inhibited by the seven compounds; the pKi values were: N-desmethylclozapine (5.33); clozapine-N-oxide (4.18); olanzapine (5.45); thioridazine (4.91); zotepine (4.75); remoxipride (4.51) and risperidone (4.43). Three compounds were examined in a functional H3 receptor model as well. The electrically evoked tritium overflow from superfused mouse brain cortex slices, which represents quasi-physiological noradrenaline release, was not affected by N-desmethylclozapine (3.2 and 10 microM), clozapine-N-oxide (3.2-100 microM) and olanzapine (3.2-32 microM). On the other hand, the three compounds shifted to the right the concentration-response curve of histamine for its inhibitory effect on the evoked overflow; the apparent pA2 values were 5.84, 4.21 and 5.80, respectively. The present study shows that five atypical neuroleptics of different chemical classes and the two major metabolites of clozapine possess a lower affinity and/or antagonistic potency at H3 receptors than clozapine itself (pKi 6.15, pA2 6.33; Kathmann M, Schlicker E, Göthert M (1994). Psychopharmacology 116: 464-468).

Topics: Animals; Antipsychotic Agents; Benzodiazepines; Binding, Competitive; Clozapine; Dibenzothiepins; Dose-Response Relationship, Drug; Histamine Antagonists; Isotope Labeling; Male; Methylhistamines; Mice; Olanzapine; Pirenzepine; Rats; Rats, Wistar; Receptors, Histamine H3; Remoxipride; Risperidone; Structure-Activity Relationship; Thioridazine; Tritium