Treatment of negative and cognitive symptoms

Persistent negative symptoms and cognitive dysfunction are a major cause of chronic disability in schizophrenia. Atypical antipsychotics such as clozapine, risperidone, and olanzapine induce significantly greater improvement in negative symptoms than that which is obtained with conventional agents. However, it remains unclear whether these agents treat core negative symptoms of schizophrenia, or simply induce less secondary psychopathology. A second approach for treatment of persistent negative symptoms is the use of N-methyl-D-aspartate (NMDA) receptor-stimulating agents, such as glycine, D-serine or D-cycloserine. These agents, when added to conventional or atypical antipsychotics, may induce significant additional reduction in both negative and cognitive symptoms.     

D-Cycloserine added to risperidone in patients with primary negative symptoms of schizophrenia

BACKGROUND: D-Cycloserine, a partial agonist at the glycine recognition site of the NMDA receptor has previously been shown to improve negative symptoms when added to conventional antipsychotics and to worsen negative symptoms when added to clozapine. The purpose of this study was to examine the effects of D-cycloserine when added to risperidone on negative symptoms of schizophrenia. METHOD: Ten patients with schizophrenia who were treated with risperidone completed consecutive two week trials of placebo and four doses of D-cycloserine. Clinical assessments were videotaped and were scored by a rater who was blind to temporal sequence. RESULTS: D-Cycloserine at a dose of 50mg/day was associated with significant reduction in negative symptoms (mean=10%). Ratings of depression, extrapyramidal side effects, and cognitive function were unchanged. Serum concentrations of glutamate and serine increased significantly on this dose of D-cycloserine. CONCLUSIONS: This preliminary study suggests that combination of D-cycloserine, 50mg/day, with risperidone may improve negative symptoms of schizophrenia over a narrow dose range. The degree of improvement appears to be intermediate between improvement of negative symptoms observed with combination of D-cycloserine with conventional antipsychotics and worsening of negative symptoms observed with combination of D-cycloserine with clozapine in previous trials of identical design.     

Placebo-controlled trial of glycine added to clozapine in schizophrenia

OBJECTIVE: The purpose of this study was to evaluate the effects of high-dose oral glycine on positive and negative symptoms and cognitive function when added to clozapine in adults with schizophrenia. METHOD: The authors conducted a double-blind, placebo-controlled, parallel-group trial of 60 g/day of glycine added to clozapine for 8 weeks in 30 adults with schizophrenia. Clinical ratings were performed every 2 weeks. RESULTS: Twenty-seven patients completed the trial. Glycine augmentation of clozapine produced no statistically significant change in positive or negative symptoms or cognitive functioning. No subjects showed clinically significant worsening of clinical ratings. CONCLUSIONS: These data, combined with data from previous trials with D-cycloserine and glycine, suggest that agonists at the glycine site may be less effective when combined with clozapine than they are when combined with conventional antipsychotics.     

Management of negative symptoms of schizophrenia

Persistent negative symptoms are a major cause of chronic disability in schizophrenia. The primary management approach for negative symptoms is use of atypical antipsychotics. Among atypical antipsychotics, clozapine produces the most robust reductions in negative symptoms. Lesser degrees of reduction are observed with risperidone and olanzapine. However, it remains unclear whether these agents treat core negative symptoms of schizophrenia, or simply induce less secondary psychopathology. A second approach for treatment of persistent negative symptoms is the use of N-methyl-D-aspartate (NMDA) receptor-stimulating agents, such as glycine, D-serine, or D-cycloserine. Significant benefit of these agents has been observed in combination with both conventional and newer atypical antipsychotics. Whether or not these agents are effective in combination with clozapine remains an open question, and large scale multicenter clinical trials are ongoing.     

Management of negative symptoms of schizophrenia

Persistent negative symptoms are a major cause of chronic disability in schizophrenia. The primary management approach for negative symptoms is use of atypical antipsychotics. Among atypical antipsychotics, clozapine produces the most robust reductions in negative symptoms. Lesser degrees of reduction are observed with risperidone and olanzapine. However, it remains unclear whether these agents treat core negative symptoms of schizophrenia, or simply induce less secondary psychopathology. A second approach for treatment of persistent negative symptoms is the use of N-methyl-D-aspartate (NMDA) receptor-stimulating agents, such as glycine, D-serine, or D-cycloserine. Significant benefit of these agents has been observed in combination with both conventional and newer atypical antipsychotics. Whether or not these agents are effective in combination with clozapine remains an open question, and large scale multicenter clinical trials are ongoing.     

D-serine efficacy as add-on pharmacotherapy to risperidone and olanzapine for treatment-refractory schizophrenia.

BACKGROUND: D-serine, a selective full agonist at the glycine site of N-methyl-D-aspartate glutamate receptor, might presently be the compound of choice for counteracting the hypothesized dysfunction of this receptor class in schizophrenia. Studies performed with Taiwanese patients indicate that D-serine significantly improves schizophrenia symptoms when used as adjuvant to conventional neuroleptics but not to clozapine. We assessed the efficacy and safety of D-serine adjuvant treatment for Occidental schizophrenia patients treated with newer atypical antipsychotics. METHODS: Thirty-nine risperidone- or olanzapine-treated schizophrenia patients participated in a double-blind, placebo-controlled, 6-week crossover trial with 30 mg/kg/day D-serine added to their antipsychotic medication. Measures of clinical efficacy and side effects were determined biweekly throughout the study. Clinical laboratory parameters and amino acid serum levels were monitored. RESULTS: D-serine administration induced increased serine serum levels (p < .001) and resulted in significant (p < .001) improvements in negative, positive, cognitive, and depression symptoms, as measured by the Positive and Negative Syndrome Scale. For approximately one third of the sample, D-serine treatment resulted in significant (>20%) reductions in Brief Psychiatric Rating Scale total scores. D-serine was well tolerated, and no detrimental changes in clinical laboratory parameters were noted. CONCLUSIONS: These findings 1) indicate that risperidone and olanzapine efficacy might be augmented with D-serine adjuvant treatment; 2) confirm D-serine efficacy against main schizophrenia symptom domains; and 3) warrant the assessment of D-serine antipsychotic monotherapy for this illness.     

Clozapine, olanzapine, risperidone, and haloperidol in the treatment of patients with chronic schizophrenia and schizoaffective disorder

OBJECTIVE: The authors compared the efficacy and safety of three atypical antipsychotics (clozapine, olanzapine, and risperidone) with one another and with haloperidol in the treatment of patients with chronic schizophrenia or schizoaffective disorder. METHOD: In a double-blind trial, 157 inpatients with a history of suboptimal treatment response were randomly assigned to treatment with clozapine, olanzapine, risperidone, or haloperidol for 14 weeks (an 8-week escalation and fixed-dose period followed by a 6-week variable-dose period). RESULTS: Clozapine, risperidone, and olanzapine (but not haloperidol) resulted in statistically significant improvements in total score on the Positive and Negative Syndrome Scale. Improvements seen in total and negative symptom scores with clozapine and olanzapine were superior to haloperidol. The atypical drugs, particularly olanzapine and clozapine, were associated with weight gain. CONCLUSIONS: The effects of atypical antipsychotics in this population were statistically significant but clinically modest. The overall pattern of results suggests that clozapine and olanzapine have similar general antipsychotic efficacy and that risperidone may be somewhat less effective. Clozapine was the most effective treatment for negative symptoms. However, the differences among treatments were small.     

A placebo-controlled crossover trial of D-cycloserine added to clozapine in patients with schizophrenia.

BACKGROUND: D-Cycloserine, a partial agonist at the glycine recognition site of the NMDA receptor, has previously been shown to improve negative symptoms when added to conventional antipsychotics and, in one preliminary dose-finding study, worsened negative symptoms when added to clozapine. METHODS: Seventeen schizophrenia outpatients treated with clozapine were assigned in random order to 6-week trials of D-cycloserine 50 mg/day and placebo in a crossover design separated by a 1 week placebo washout. RESULTS: Eleven patients competed the 13-week study. D-Cycloserine significantly worsened ratings of negative symptoms compared to placebo but did not significantly affect ratings of psychotic symptoms. CONCLUSIONS: The differing effects of D-cycloserine on negative symptoms when added to clozapine compared to conventional antipsychotics suggests that activation of the glycine recognition site may play a role in clozapine's efficacy for negative symptoms.     

D-serine added to clozapine for the treatment of schizophrenia.

OBJECTIVE: D-Serine is a full agonist at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. Previous administration of D-serine to schizophrenic patients taking nonclozapine antipsychotics improved positive, negative, and cognitive symptoms, whereas the partial agonist D-cycloserine improved negative symptoms of patients taking conventional antipsychotics but worsened symptoms in clozapine-treated patients. To study the difference between full and partial agonists at the NMDA receptor glycine site, the clinical effects of adding D-serine to clozapine were assessed. METHOD: In a 6-week double-blind trial, 20 schizophrenic patients received placebo or D-serine (30 mg/kg per day) in addition to clozapine. Clinical efficacy, side effects, and serum levels of D-serine were determined every other week. RESULTS: The patients exhibited no improvement with D-serine, nor did their symptoms worsen, as previously reported with D-cycloserine. CONCLUSIONS: The results suggest either that clozapine may have an agonistic effect on the NMDA system or that clozapine-treated patients do not respond to D-serine.     

Serum leptin and triglyceride levels in patients on treatment with atypical antipsychotics

BACKGROUND: Weight gain is a common adverse effect associated with the use of most antipsychotic drugs. Leptin has been reported to be associated with antipsychotic-induced weight gain. Previous studies have demonstrated a relationship between the atypical antipsychotics clozapine and olanzapine and serum leptin levels. We planned to comparatively investigate the effects of the atypical antipsychotics quetiapine, olanzapine, risperidone, and clozapine on leptin and triglyceride levels and weight gain. METHOD: The study population comprised 56 patients with DSM-IV schizophrenia, who were divided into 4 treatment groups: quetiapine (N = 14), olanzapine (N = 14), risperidone (N = 14), or clozapine (N = 14) monotherapy, and a control group of 11 patients receiving no psychopharmacologic treatment. The patients were evaluated at baseline and at the sixth week according to the Positive and Negative Syndrome Scale (PANSS), body mass index (BMI), weight, and fasting serum leptin and triglyceride levels. Data were gathered in 2001 and 2002. RESULTS: Olanzapine and clozapine caused a marked increase in weight and serum triglyceride and leptin levels, though increases in these variables were modest in the patients receiving quetiapine and minimal in those receiving risperidone. There were positive correlations between serum leptin levels and BMI and triglyceride levels. Clinical efficacy, as indicated by decrease in total PANSS scores, was associated with leptin levels in all atypical antipsychotic groups. CONCLUSION: Our results suggest that leptin may be associated with olanzapine- and clozapine-induced weight gain and that quetiapine appears to have modest influence and risperidone appears to have minimal influence on leptin and triglyceride levels and weight gain compared with olanzapine and clozapine.     

Effects of atypical antipsychotics on the syndromal profile in treatment-resistant schizophrenia

BACKGROUND: There has been considerable support for the observation that atypical antipsychotics have a broader range of therapeutic effects than traditional antipsychotics. We are exploring whether this expanded clinical efficacy can also be seen in patients with treatment-resistant schizophrenia. METHOD: The subjects were 157 treatment-resistant inpatients diagnosed with DSM-IV schizophrenia or schizoaffective disorder. They were randomly assigned to treatment with clozapine, olanzapine, risperidone, or haloperidol in a 14-week double-blind trial and rated with a standard measure of clinical antipsychotic efficacy (Positive and Negative Syndrome Scale [PANSS]). Factor analysis at baseline and endpoint together with changes in 5 PANSS-derived factors were examined. Data were gathered from June 1996 to December 1999. RESULTS: The underlying PANSS factor structure, as indicated by the factor loadings, was essentially identical at baseline and endpoint. At baseline, the excitement factor was followed by the positive, negative, cognitive, and depression/anxiety factors, explaining 49.4% of the total variance. At endpoint, the positive factor was followed by the negative, excitement, cognitive, and depression/anxiety factors, explaining 55.5% of the total variance. The endpoint data indicated statistically significant (p <.05) improvements over time on the positive factor for all 3 atypicals, but not for haloperidol. The negative factor showed significant improvement for clozapine and olanzapine, with significant worsening for haloperidol. Clozapine, olanzapine, and risperidone were superior to haloperidol on the negative factor, while clozapine was also superior to risperidone. The cognitive factor showed significant improvement for all atypicals, as did the depression/anxiety factor. Only clozapine showed improvement on the excitement factor and was superior to both haloperidol and risperidone. CONCLUSIONS: Treatment with atypical antipsychotics did not substantially change the underlying PANSS 5-factor structure. However, antipsychotic treatment with all 3 atypical medications was associated with significant improvements on 3 of 5 syndromal domains (positive, cognitive, and depression/anxiety) of schizophrenia. Clozapine and olanzapine also showed improvement on the negative factor. Only clozapine was associated with improvement on the excitement domain. This finding confirms that atypicals are associated with improvement of an expanded spectrum of symptoms in treatment-resistant patients.     

Topiramate add-on in treatment-resistant schizophrenia: a randomized, double-blind, placebo-controlled, crossover trial

OBJECTIVE: We tested the hypothesis that topiramate is more effective than placebo in reducing symptoms in patients with treatment-resistant schizophrenia when combined with ongoing antipsychotic medication. METHOD: Twenty-six hospitalized treatment-resistant patients with chronic DSM-IV-diagnosed schizophrenia participated in a randomized, double-blind, placebo-controlled trial in which 300 mg/day of topiramate was gradually added to their ongoing treatment (clozapine, olanzapine, risperidone, or quetiapine) over two 12-week crossover treatment periods. Data were collected from April 2003 to November 2003. RESULTS: In intention-to-treat analysis, topiramate was more effective than placebo in reducing Positive and Negative Syndrome Scale general psychopathologic symptoms (effect size = 0.7, p = .021), whereas no significant improvement was observed in positive or negative symptoms. CONCLUSION: Glutamate antagonist topiramate may be an effective adjuvant treatment in reducing general psychopathologic symptoms in patients with schizophrenia resistant to treatment with second-generation antipsychotics.     

Cognitive deficit in schizophrenia and its neurochemical basis

Cognitive impairment is a central feature of schizophrenia and has been correlated with negative symptoms and impaired social functioning. There is a growing body of data suggesting that the so-called atypical antipsychotic drugs (e.g. clozapine, risperidone, and olanzapine) are better at enhancing cognitive function than traditional neuroleptics. Preclinical studies of information processing using a pre-pulse inhibition model show that the mechanism of action of both olanzapine and clozapine for cognitive enhancement may involve glutamatergic/N-methyl-D-aspartate (NMDA) antagonism. Using positron emission tomography, we have described the metabolic and neurochemical correlates of cognitive impairment induced by glutamatergic/NMDA antagonism. A better understanding of the underlying causes of cognitive impairment may contribute to elucidating the pathophysiology of schizophrenia and the development of more efficacious treatments for this disorder.     

Treatment with olanzapine, risperidone or typical antipsychotic drugs in Asian patients with schizophrenia

OBJECTIVE: To examine clinical outcomes in Asian patients with schizophrenia receiving monotherapy with olanzapine, risperidone or typical antipsychotics in naturalistic settings. METHOD: In this report, data from the first 12 months of the prospective, observational, 3-year Intercontinental Schizophrenia Outpatient Health Outcomes study are presented for patients from participating Asian countries (Korea, Taiwan and Malaysia) who were started on, or switched to, monotherapy with olanzapine (n = 484), risperidone (n = 287) or a typical antipsychotic drug (n = 127) at baseline. RESULTS: At 12 months, overall reduction in the score of Clinical Global Impressions-Severity of Illness rating scale was greatest with olanzapine (p < 0.001 vs typical agents), followed by risperidone (p = 0.007 vs typical agents) treatment. Olanzapine treatment was found to have significantly better effects than typical agents on negative and depressive symptom scores, and significantly greater improvements than risperidone on negative and cognitive symptoms. The occurrence of extrapyramidal symptoms was least likely with olanzapine (p < 0.001 vs typical agents, and p = 0.012 vs risperidone), while the estimated odds of tardive dyskinesia were greatest in the typical treatment group (p = 0.046 vs olanzapine, and p = 0.082 vs risperidone). Mean weight increase was greater for olanzapine-treated patients compared with the other agents (p = 0.030 vs typical agents and p < 0.001 vs risperidone). The risk of menstrual disturbance was relatively high with risperidone when compared with olanzapine treatment (p < 0.001). CONCLUSIONS: The results of this observational study indicate that, in Asian patients with schizophrenia, olanzapine may offer benefits when compared with typical agents or risperidone. However, the significantly greater odds of weight gain should be considered in the clinical management of olanzapine-treated patients.     

Sexual dysfunction and antipsychotic treatment

Human sexual function is complex and affected in many different ways by schizophrenia and the antipsychotic drugs used in its treatment. The evaluation of the effects of antipsychotics on sexual function in patients with schizophrenia is also complex because the deleterious effects of conventional antipsychotics are superimposed on the effects of the disease itself. Although not extensively researched, sexual dysfunction seems to be frequent in patients with schizophrenia, especially in men. Sexual dysfunction appears, in significant part, to be a direct consequence of dopamine antagonism, combined with indirect effects due to increased serum prolactin concentration. Atypical antipsychotics have a number of potential advantages over standard agents with regard to their impact on sexual function. Clinical reports indicate that atypical antipsychotics are associated with a lower incidence of sexual adverse events than conventional antipsychotics and that there may also be important differences between them in this regard. For example, dose-related increases in prolactin concentrations occur with risperidone whereas olanzapine is associated with mild and transient increases in long-term treatment. Treatment with clozapine does not result in prolactin elevation and, like olanzapine, only transient increases occur with ziprasidone therapy, but the risk of agranulocytosis with clozapine restricts its use. Quetiapine has no more effect on serum prolactin than placebo across its full dose range. Together with its low frequency of reproductive or hormonal side effects and a low incidence of extrapyramidal symptoms, the tolerability profile of quetiapine may be particularly beneficial for many patients. Sexual dysfunction can be an important source of distress to patients and adversely affects compliance, and is one of the factors that must be taken into account when selecting treatment.     

Effectiveness of antipsychotic treatments for schizophrenia: interim 6-month analysis from a prospective observational study (IC-SOHO) comparing olanzapine, quetiapine, risperidone, and haloperidol

BACKGROUND: The Intercontinental Schizophrenia Outpatient Health Outcomes (IC-SOHO) study was designed to provide information regarding use and outcome of antipsychotic treatments in a large, diverse population in real practice settings. METHOD: Outpatients with schizophrenia (ICD-10 or DSM-IV) who initiated or changed to a new antipsychotic entered this 3-year, naturalistic, prospective observational study. Four monotherapy treatment groups were defined according to the antipsychotic prescribed at baseline, namely olanzapine, risperidone, quetiapine, and haloperidol. Efficacy was assessed using the Clinical Global Impressions-Severity of Illness rating scale (CGI-S), inclusive of subscales for positive, negative, depressive, and cognitive symptoms. Tolerability was assessed by adverse event questionnaires and weight measurements. Six-month findings are described. RESULTS: At baseline, 5833 participants were prescribed monotherapy and the mean severity of illness was moderate to marked (CGI-S). At 6 months, olanzapine resulted in significantly greater improvements in overall, positive, negative, depressive, and cognitive symptoms compared with quetiapine, risperidone or haloperidol (p <.001). Improvements in overall, negative, and cognitive symptoms were significantly higher for risperidone compared with haloperidol (p <.001), whereas improvements across all symptoms were comparable for quetiapine and haloperidol. Extra-pyramidal symptoms and tardive dyskinesia decreased compared with baseline in the olanzapine, quetiapine, and risperidone groups but increased in the haloperidol group (p <.001, likelihood of extrapyramidal symptoms with haloperidol compared with olanzapine, quetiapine, or risperidone). Sexual function adverse events were most prominent in the haloperidol and risperidone treatment groups. Weight change was significantly greater for olanzapine compared with the other antipsychotics (p <.001). CONCLUSION: Our results support the previously reported positive impact of atypical antipsychotics, particularly olanzapine, in patients with schizophrenia.     

Olanzapine vs. other antipsychotics in actual out-patient settings: six months tolerability results from the European Schizophrenia Out-patient Health Outcomes study

OBJECTIVE: The European Schizophrenia Out-patient Health Outcomes study is an observational study investigating treatment in schizophrenia. We report treatment-emergent adverse events during the first 6 months of treatment. METHOD: The rate of extrapyramidal symptoms (EPS), anticholinergic use, weight gain and sexual related dysfunctions were assessed in 8,400 out-patients. RESULTS: Patients typical antipsychotics and risperidone experienced significantly more EPS and anticholinergic use than patients in the clozapine, olanzapine, and quetiapine cohorts. Patients treated with amisulpride, typical antipsychotics and risperidone were significantly more likely to have sexual related dysfunctions and/or amenorrhea. Increases in weight and body mass index occurred in all cohorts, but were significantly greater in the olanzapine and clozapine cohorts. CONCLUSION: Patients treated with olanzapine, quetiapine and clozapine had better tolerability outcomes regarding EPS and sexual related dysfunctions compared with patients receiving risperidone, amisulpride and typicals. Patients treated with olanzapine and clozapine had higher weight increases than patients treated with risperidone, quetiapine and typicals.     

The efficacy of atypical antipsychotics in the treatment of depressive symptoms, hostility, and suicidality in patients with schizophrenia

Depressive symptoms and syndromal depression commonly occur in patients with schizophrenia. Schizophrenia is also associated with aggression directed at self and others. For this article, the available literature regarding the efficacy of clozapine, risperidone, olanzapine, quetiapine, and ziprasidone in the treatment of depression, hostility, and suicidality in patients with schizophrenia was reviewed. These studies suggest that atypical antipsychotics may exert therapeutic effects on depression and hostility as well as psychosis and that clozapine and olanzapine may reduce suicidality in patients with schizophrenia. These therapeutic actions appear to represent additional advantages of atypical antipsychotics compared with standard agents.     

Differences in prolactin elevation and related symptoms of atypical antipsychotics in schizophrenic patients

OBJECTIVE: The aim of this cross-sectional study was to investigate the degree and frequency of prolactin (PRL) elevation and related symptoms in patients treated with 3 different atypical antipsychotics: clozapine, olanzapine, and risperidone. METHOD: Twenty-eight patients receiving clozapine, 29 patients receiving olanzapine, and 18 patients receiving risperidone (all meeting DSM-IV criteria for schizophrenia, schizophreni-form disorder, or schizoaffective disorder) were studied. The median daily dose was 400 mg of clozapine, 10 mg of olanzapine, and 3 mg of risperidone. Fasting morning blood samples were analyzed for PRL, and the occurrence of hyper-prolactinemic symptoms in the patients was evaluated. RESULTS: Elevated PRL levels were found in 16 (89%) of the patients receiving risperidone and in 7 (24%) of the patients receiving olanzapine, but in none of the patients receiving clozapine. In addition, there was a significant difference in median PRL level among the treatment groups (p < .0001), in that the PRL level was higher both in the patients treated with risperidone and in the patients treated with olanzapine, compared to those treated with clozapine. Moreover, hyperpro-lactinemic symptoms-menstrual disturbances, galactorrhea, impotence, oligospermia, and decreased libido-were reported in 8 (44%) of the risperidone-treated patients and in 1 (3%) of the olanzapine-treated patients, but in none of the clozapine-treated patients. CONCLUSION: Treatment with risperidone was frequently associated with hyperprolactinemia and related symptoms, whereas the occurrence of PRL elevation and related symptoms was modest in patients receiving olanzapine and nonexistent in those receiving clozapine. Thus, atypical anti-psychotics in therapeutic doses differ with regard to effect on PRL secretion.     

Atypical antipsychotics suppress production of proinflammatory cytokines and up-regulate interleukin-10 in lipopolysaccharide-treated mice

There is considerable evidence that schizophrenia is associated with immune system dysregulation. For example, blood and cerebrospinal fluid (CSF) levels of proinflammatory cytokines are significantly increased in schizophrenic patients, and their normalization correlates with improvement in psychotic symptoms. In fact, typical and atypical antipsychotics are reported to modulate immune function in in vitro and in vivo studies. In the present study, we examined the anti-inflammatory effect of antipsychotics, clozapine, olanzapine, risperidone and haloperidol, on serum cytokine levels in lipopolysaccharide (LPS)-treated mice. Atypical antipsychotics, such as clozapine, olanzapine and risperidone, but not haloperidol, suppressed tumor necrosis factor (TNF)-α and interleukin (IL)-6, and up-regulated IL-10. Moreover, only clozapine, robustly increased the serum levels of IL-10. Clozapine reproduced its anti-inflammatory feature in polyinsinic–polycytidylic acid sodium salt (Poly[I:C])-induced inflammation. Thus, the anti-inflammatory effect of clozapine would adapt to inflammation induced by some varieties of antigens. Several receptor ligands, such as 8-OH-DPAT, ketanserin, prazosin and scopolamine, were also examined as to their anti-inflammatory effects on serum cytokine levels in LPS-treated mice. Ketanserin and prazosin, but not 8-OH-DPAT nor scopolamine, behaved similarly to atypical antipsychotics. However, the remarkable increase of serum IL-10 level observed in clozapine was not detected in ketanserin and prazosin. These results suggest the unique efficacy of atypical antipsychotics in the suppression of proinflammatory cytokines, and the increase of anti-inflammatory cytokine, IL-10.