Increased dopamine d(2) receptor occupancy and elevated prolactin level associated with addition of haloperidol to clozapine

Effect of Apigenin on Neurodegenerative Diseases

Neurodegenerative diseases (NDDs), such as Alzheimer's and Parkinson's, are the most frequent age-related illnesses affecting millions worldwide. No effective medication for NDDs is known to date and current disease management approaches include neuroprotection strategies with the hope of maintaining and improving the function of neurons. Such strategies will not provide a cure on their own but are likely to delay disease progression by reducing the production of neurotoxic chemicals such as reactive oxygen species (ROS) and related inflammatory chemicals. Natural compounds such as flavonoids that provide neuroprotection via numerous mechanisms have attracted much attention in recent years. This review discusses evidence from different research models and clinical trials on the therapeutic potential of one promising flavonoid, apigenin, and how it can be helpful for NDDs in the future prospects. We have also discussed its chemistry, mechanism of action, and possible benefits in various examples of NDDs.

The historical progression of positron emission tomography research in neuroendocrinology

The rapid and continual development of a number of radiopharmaceuticals targeting different receptor, enzyme and small molecule systems has fostered Positron Emission Tomography (PET) imaging of endocrine system actions in vivo in the human brain for several decades. PET radioligands have been developed to measure changes that are regulated by hormone action (e.g., glucose metabolism, cerebral blood flow, dopamine receptors) and actions within endocrine organs or glands such as steroids (e.g., glucocorticoids receptors), hormones (e.g., estrogen, insulin), and enzymes (e.g., aromatase). This systematic review is targeted to the neuroendocrinology community that may be interested in learning about positron emission tomography (PET) imaging for use in their research. Covering neuroendocrine PET research over the past half century, researchers and clinicians will be able to answer the question of where future research may benefit from the strengths of PET imaging.

Challenges in the clinical development of non-D2 compounds for schizophrenia

Schizophrenia is a chronic, heterogeneous, severe psychiatric disorder characterized by a spectrum of symptomology and is associated with substantial morbidity and mortality. For the last 70 years, available treatments have shared blockade of dopamine D2 receptors as their primary mechanism of action (MOA), the efficacy of which has been limited by incomplete resolution of all symptoms as well as treatment non-response in a select subset of patients. In addition, antipsychotics are associated with class-related side effects attributed to this primary MOA, including extrapyramidal symptoms (EPS). The need for non-D2 treatment options for patients which offer a novel risk/benefit profile is therefore apparent. There has been substantial investment in the research and development of non-D2 drug candidates. However, none of these programs have received successful regulatory approval by the FDA (as of Oct 2022). In this article, the scale of industry-sponsored clinical trials for D2-based investigational pharmacological treatments in schizophrenia was quantified and compared with investigational compounds with non-D2 MOAs. In a dataset of 545 clinical trials identified in ClinicalTrials.gov from January 2002 to July 2022, total enrollments in trials of non-D2-based compounds for the treatment of schizophrenia summed to approximately 34,000 patients, compared with 27,144 patients for D2-based compounds. These data indicate that there remains substantial and ongoing investment in the development of novel non-D2 options for schizophrenia, with a success rate measured by regulatory approval that is well-below recent benchmarks for the broader category of CNS drugs. Improved trial design, conduct, endpoints, and analyses/methods may influence signal detection and reliability to support development and registration of non-D2 compounds.

Antipsychotics: Mechanisms underlying clinical response and side-effects and novel treatment approaches based on pathophysiology

Antipsychotic drugs are central to the treatment of schizophrenia and other psychotic disorders but are ineffective for some patients and associated with side-effects and nonadherence in others. We review the in vitro, pre-clinical, clinical and molecular imaging evidence on the mode of action of antipsychotics and their side-effects. This identifies the key role of striatal dopamine D2 receptor blockade for clinical response, but also for endocrine and motor side-effects, indicating a therapeutic window for D2 blockade. We consider how partial D2/3 receptor agonists fit within this framework, and the role of off-target effects of antipsychotics, particularly at serotonergic, histaminergic, cholinergic, and adrenergic receptors for efficacy and side-effects such as weight gain, sedation and dysphoria. We review the neurobiology of schizophrenia relevant to the mode of action of antipsychotics, and for the identification of new treatment targets. This shows elevated striatal dopamine synthesis and release capacity in dorsal regions of the striatum underlies the positive symptoms of psychosis and suggests reduced dopamine release in cortical regions contributes to cognitive and negative symptoms. Current drugs act downstream of the major dopamine abnormalities in schizophrenia, and potentially worsen cortical dopamine function. We consider new approaches including targeting dopamine synthesis and storage, autoreceptors, and trace amine receptors, and the cannabinoid, muscarinic, GABAergic and glutamatergic regulation of dopamine neurons, as well as post-synaptic modulation through phosphodiesterase inhibitors. Finally, we consider treatments for cognitive and negative symptoms such dopamine agonists, nicotinic agents and AMPA modulators before discussing immunological approaches which may be disease modifying. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

Psychopharmacological Treatment of Schizophrenia Over Time in 30 908 Inpatients: Data From the AMSP Study

BACKGROUND

Psychotropic drugs are the cornerstone of schizophrenia treatment, often requiring lifelong treatment. Data on pharmacotherapy in inpatient settings are lacking.

METHODS

Prescription data of schizophrenic inpatients within the time period 2000-2015 were obtained from the database of the Drug Safety Program in Psychiatry (AMSP). Data were collected at 2 index dates per year; the prescription patterns and changes over time were analyzed.

RESULTS

Among 30 908 inpatients (mean age 41.6 years, 57.8% males), the drug classes administered most often were antipsychotics (94.8%), tranquilizers (32%), antidepressants (16.5%), antiparkinsonians (16%), anticonvulsants (14.1%), hypnotics (8.1%), and lithium (2.1%). The use of second-generation antipsychotics significantly increased from 62.8% in 2000 to 88.9% in 2015 (P < .001), whereas the prescription of first-generation antipsychotics decreased from 46.6% in 2000 to 24.7% in 2015 (P < .001). The administration of long-acting injectable antipsychotics decreased from 15.2% in 2000 to 11.7% in 2015 (P = .006). Clopazine was the most often used antipsychotic, having been used for 21.3% of all patients. Polypharmacy rates (≥5 drugs) increased from 19% in 2000 to 26.5% in 2015. Psychiatric polypharmacy (≥3 psychotropic drugs) was present in 44.7% of patients.

CONCLUSIONS

Combinations of antipsychotics and augmentation therapies with other drug classes are frequently prescribed for schizophrenic patients. Though treatment resistance and unsatisfactory functional outcomes reflect clinical necessity, further prospective studies are needed on real-world prescription patterns in schizophrenia to evaluate the efficacy and safety of this common practice.

Hypothalamic-pituitary-gonadal axis dysfunction: An innate pathophysiology of schizophrenia?

The female hormone 17β-estradiol is postulated to be protective against schizophrenia onset and severity. Hypoestrogenism is a common phenomenon in women with schizophrenia that has serious effects that adds to the burden of an already very onerous disease. The cause of hypoestrogenism is largely attributed to antipsychotic-induced hyperprolactinemia. Evidence suggest however that a significant portion of female schizophrenia patients develop hypoestrogenism either before antipsychotic treatment or without regard to the level of prolactin, suggesting that for a sizeable segment of female patients, gonadal abnormality may be an innate and early aspect of the disease. This review aims to summarise the available literature that examines gonadal dysfunction in schizophrenia through this prism as well as to outline some recent developments in treatment strategies that may provide feasible ways to successfully tackle hypoestrogenism in schizophrenia.

Dopamine D2 receptor occupancy of lumateperone (ITI-007): a Positron Emission Tomography Study in patients with schizophrenia

Dopamine D₂ receptor occupancy (D₂RO) is a key feature of all currently approved antipsychotic medications. However, antipsychotic efficacy associated with high D₂RO is often limited by side effects such as motor disturbances and hyperprolactinemia. Lumateperone (ITI-007) is a first-in-class selective and simultaneous modulator of serotonin, dopamine and glutamate in development for the treatment of schizophrenia and other disorders. The primary objective of the present study was to determine D₂RO at plasma steady state of 60 mg ITI-007, a dose that previously demonstrated antipsychotic efficacy in a controlled trial, administered orally open-label once daily in the morning for two weeks in patients with schizophrenia (N = 10) and after at least a two-week washout period from standard of care antipsychotics. D₂RO was determined using positron emission tomography with ¹¹C-raclopride as the radiotracer. Mean peak dorsal striatal D₂RO was 39% at 60 mg ITI-007 occurring 1 h post-dose. Lumateperone was well-tolerated with a favorable safety profile in this study. There were no clinically significant changes in vital signs, ECGs, or clinical chemistry laboratory values, including prolactin levels. There were no adverse event reports of akathisia or other extrapyramidal motor side effects; mean scores on motor function scales indicated no motor disturbances with lumateperone treatment. This level of occupancy is lower than most other antipsychotic drugs at their efficacious doses and likely contributes to the favorable safety and tolerability profile of lumateperone with reduced risk for movement disorders and hyperprolactinemia. If approved, lumateperone may provide a new and safe treatment option for individuals living with schizophrenia.

Co-prescribing of atypical and typical antipsychotics – prescribing sequence and documented outcome

AIMS AND METHOD

To evaluate patterns of antipsychotic co-prescription and to establish documented outcome, we reviewed 1441 in-patient and community prescriptions written in a large mental health trust. For patients co-prescribed regular atypical and typical antipsychotics for longer than 6 weeks, medication histories were taken and case notes examined to determine sequence of prescribing, documented outcome and reasons for co-prescription.

RESULTS

Fifty-three patients had been co-prescribed aytpical and typical antipsychotics for more than 6 weeks. In 62% of cases the atypical drug had been prescribed first and a typical drug added later. The most frequently documented reason for co-prescription was that symptoms persisted when prescribed a single antipsychotic. Clinical outcome was documented for 64% of patients: 45% of the total number treated showed some improvement, with seven of 53 patients noted to have shown improvements in psychotic symptoms.

CLINICAL IMPLICATIONS

Co-prescription of aytpical and typical antipsychotics often occurs as a consequence of poor outcome with single drug treatment. In this study there was minimal evidence to suggest that co-prescription improved outcome to an important extent. There remains little support for co-prescription of antipsychotics but considerable evidence to suggest that such practice worsens adverse effect burden. Co-prescription of atypical and typical antipsychotics should be avoided in all but very exceptional circumstances.

Representativeness of clinical PET study participants with schizophrenia: A systematic review

While positron emission tomography (PET) studies have provided invaluable data on antipsychotic effects, selection bias remains a serious concern. A systematic review of PET studies that measured dopamine D₂ receptor blockade with antipsychotics was conducted to examine their inclusion/exclusion criteria, using PubMed, EMBASE, and ClinicalTrials.gov (last search, September 2016). PET studies were included if they measured D₂ receptor occupancy in patients with schizophrenia and included introduction of antipsychotic treatment or antipsychotic regimen change in a systematic manner. Twenty-six studies were identified. Age limit was included in 13 studies; one study solely included geriatric patients while others targeted younger adults. Eleven, 6, and 3 studies specifically targeted clinically stable patients, patients with severe psychopathology, and antipsychotic-free patients, respectively. Nineteen and 18 studies excluded patients with physical comorbidity and substance abuse, respectively. As a result, the mean age of subjects ranged from 23 to 42 years when one study that targeted geriatric patients was excluded. Mean Positive and Negative Syndrome Scale total scores ranged from 54 to 95. No comparison active-drug or placebo arm was employed in 24 studies. Blind assessment of symptomatology was performed in 5 studies. In general, subjects participating in clinical PET studies were relatively young, presented with mild symptomatology, and were free from substance abuse or physical comorbidities. These characteristics need to be taken into account when clinical PET data are interpreted. On the other hand, it should also be noted that this study was only qualitative and conservative interpretation is necessary for possibility of subjective bias.

Brexpiprazole for the treatment of schizophrenia

INTRODUCTION

Limited efficacy on negative and cognitive symptoms and adverse effects of current antipsychotics raise the need of developing new antipsychotics. Brexpiprazole, a new antipsychotic drug approved by the U.S. Food and Drug Administration in July 2015 for the treatment of schizophrenia, is a novel serotonin-dopamine receptor modulator with partial agonist activity at serotonin 1A (5-HT_1A) and D_2/3 receptors. Areas covered: We reviewed brexpiprazole related in vitro and in vivo studies, including phase II and phase III clinical trials in this article. Brexpiprazole showed significant improvement of psychotic symptoms for patients with schizophrenia in clinical trials. Most of the clinical trials demonstrated the antipsychotic effect of brexpiprazole using Positive and Negative Syndrome Scale (PANSS) in acute schizophrenia patients, and found that higher doses (2-4 mg daily) of brexpiprazole had better outcomes. In short-term trials, brexpiprazole did not show benefit for cognitive function in 6 weeks. Insomnia, akathisia, headache, and agitation were the most frequently recorded adverse events. Expert commentary: Brexpiprazole showed better efficacy than placebo in acute phase of schizophrenia. Long-term studies are needed to investigate the efficacy of brexpiprazole for cognitive function as well as the strength and weakness of brexpiprazole among current antipsychotic drugs.

Clozapine in schizophrenia and its association with treatment satisfaction and quality of life: Findings of the three national surveys on use of psychotropic medications in China (2002-2012)

OBJECTIVE

We examined the time trends and correlates of clozapine use in schizophrenia patients in China.

METHOD

A total of 14,013 patients with schizophrenia treated in 45 psychiatric hospitals/centers nationwide were interviewed in 2002, 2006 and 2012. Patients' socio-demographic and clinical characteristics including psychopathology, medication side effects, satisfaction with treatment and quality of life (QOL) were recorded in a standardized fashion.

RESULTS

Clozapine was used in 32.9% of the whole sample; with corresponding figures of 39.7%, 32.5% and 26.4% in 2002, 2006 and 2012 (p<0.001). Families of clozapine users had lower satisfaction with treatment than those of the non-clozapine group, without significant differences with respect to patients' treatment satisfaction and mental or physical QOL. In multiple logistic regression analyses, compared to the non-clozapine group, patients on clozapine had an earlier age of onset, longer illness duration, more global illness severity and drug-induced central nervous system, gastrointestinal and other side effects, lower antipsychotic doses, less delusions and hallucinations, more negative symptoms, were more likely male, inpatients, to have a family history of psychiatric disorders, receive treatments in regional centers and receive antipsychotic polypharmacy, but less likely to have health insurance and receive first-generation antipsychotics and benzodiazepines (R(2)=0.498, p<0.001).

CONCLUSIONS

Clozapine was used in one-third of schizophrenia patients in China, with decreasing frequency since 2002. Patients prescribed clozapine had multiple markers of greater global illness severity/chronicity and decreased satisfaction with treatment by the families, but similar QOL and less delusions and hallucinations than patients not prescribed clozapine.

Use of clozapine in older Asian patients with schizophrenia between 2001 and 2009

BACKGROUND

To date there has been no large-scale international study that examined the use of clozapine in older patients with schizophrenia. This study examined the use of clozapine and its demographic and clinical correlates in older patients with schizophrenia in East Asia during the period between 2001 and 2009.

METHOD

Information on 1,157 hospitalized patients with schizophrenia aged 50 or older in five East Asian countries and territories (China, Hong Kong, Korea, Singapore and Taiwan) was extracted from the database of the Research on Asian Psychotropic Prescription Patterns (REAP) project. Socio-demographic and clinical characteristics and prescription of psychotropic medications were recorded.

RESULTS

Clozapine was prescribed for 20.6% of the pooled sample; 19.0% in 2001, 19.4% in 2004 and 22.9% in 2009. Multiple logistic regression analysis of the whole sample revealed that patients taking clozapine had a longer duration of illness, more negative symptoms and were less likely to receive first generation antipsychotic and anticholinergic drugs, but more likely to report weight gain compared to those not receiving clozapine. Compared to those in other sites, older patients in China were more likely to receive clozapine.

CONCLUSIONS

The prescription of clozapine for older Asian schizophrenia inpatients has remained at a stable level during the past decade. The appropriateness of use of clozapine in China needs to be further explored.

Antipsychotic polypharmacy in psychotic disorders: a critical review of neurobiology, efficacy, tolerability and cost effectiveness

OBJECTIVE

The purpose of this study was to review the scientific evidence for neurobiological rationale, efficacy, tolerability and cost effectiveness of antipsychotic polypharmacy (APP).

DATA SOURCES

A systematic literature search of Medline, Embase, Ovid and the Cochrane Database of Systematic Reviews until April 2012 was carried out.

RESULTS

Theories behind APP have only modest pre-clinical and clinical evidence. We found limited statistical evidence supporting modest efficacy of APP in patients with psychotic symptoms refractory to clozapine. APP is associated with increased mortality, metabolic syndrome, decreased cognitive functioning, high dose prescription and non-adherence. It brings up extra costs, lacking evidence for cost-effectiveness.

CONCLUSIONS

Pre-clinical studies underpinning neurobiological hypotheses in APP are lacking. Evidence supporting efficacy of APP is limited with modest beneficial clinical relevance. APP is associated with several serious adverse effects and increased health costs. In the absence of more convincing pre-clinical support and clinical evidence we advise adherence to existing guidelines and limiting combinations of antipsychotics (in consideration with other pharmacotherapeutic, somatic and psychotherapeutic options) to patients with clozapine-refractory psychosis in well-evaluated individual trials that might need 10 weeks or more.

Payer types associated with antipsychotic polypharmacy in an ambulatory care setting

Objectives

Antipsychotic polypharmacy is increasingly prescribed despite little documented evidence of a therapeutic benefit. There is also a limited understanding of the role that health insurance plays on the prevalence of antipsychotic polypharmacy. This study was undertaken to investigate the relationship between antipsychotic polypharmacy and individuals' intended source of payment in a US national sample of ambulatory care patients.

Methods

The study combined 2002, 2003 and 2004 data from the National Ambulatory Medical Care Survey (NAMCS) among adults seeking outpatient-based physician medical care services in the USA. We investigated characteristic differences among patients who were prescribed multiple antipsychotics versus individuals receiving only a single antipsychotic medication. Multivariable logistic regression examined the association between antipsychotic polypharmacy and patients' primary payment type classified as private insurance, Medicaid, Medicare or other (primarily out-of-pocket) payment type.

Key findings

Use of more than one antipsychotic agent was recorded in 68 of 830 (8.2%) outpatient physician visits in the 3-year period 2002–2004. Among the payer types studied, Medicaid payment status was correlated with increased risk of antipsychotic polypharmacy (odds ratio 2.7, 95% confidence interval 1.1–6.7).

Conclusions

Insurance status was associated with antipsychotic polypharmacy among non-institutionalized US residents prescribed antipsychotic medications. Patients reporting Medicaid as their primary payer were nearly three times as likely to be prescribed multiple antipsychotic drugs, potentially increasing their risk of adverse side effects as well as greater taxpayer burden. Future research should determine whether these trends continued after 2004 and to determine the costs of treating patients in the public sector with multiple antipsychotic drugs, a common scenario despite financial pressures and uncertain medical benefit.

Characteristics and clinical correlates of prospective memory performance in first-episode schizophrenia

OBJECTIVE

The aim of this study was to examine prospective memory (PM) and its socio-demographic, clinical, and neurocognitive correlates in first episode schizophrenia (FES).

METHODS

Fifty-one FES patients and 42 healthy controls formed the study sample. Time- and event-based PM (TBPM and EBPM) performance were measured with the Chinese version of the Cambridge Prospective Memory Test (C-CAMPROMPT). A battery of neuropsychological tests was also administered. Patients' clinical symptoms were evaluated with the Positive and Negative Symptom Scale (PANSS).

RESULTS

Patients performed significantly worse in both TBPM (8.7 ± 5.3 vs. 14.8 ± 3.5) and EBPM (11.3 ± 4.7 vs. 15.7 ± 2.7) than the controls. After controlling for age, gender, education level and neurocognitive test score, the difference in performance on the two types of PM tasks between patients and controls was no longer present. In multiple linear regression analyses, longer duration of untreated psychosis (DUP), lower scores of the Hopkins Verbal Learning Test-Revised (HVLT-R) and the categories completed of the Wisconsin Card Sorting Test (WCST-CC) and higher score of the Color Trails Test-2 (CTT-2) contributed to poorer TBPM performance, while lower score of HVLT-R, higher score of the perseverative errors of the Wisconsin Card Sorting Test (WCST-PE) and longer DUP contributed to worse performance on EBPM.

CONCLUSIONS

Both subtypes of PM are impaired in first-episode schizophrenia suggesting that PM deficits are an integral part of the cognitive dysfunction in the disease process.

Long-term antipsychotic polypharmacy: how does it start, why does it continue?

BACKGROUND

Antipsychotic polypharmacy remains a widespread and persistent practice, despite a lack of empirical evidence to support its safety and efficacy. This study aimed to assess antipsychotic treatment prior to the initiation of polypharmacy and ascertained clinicians' reasons for coprescribing long term. We also aimed to determine patterns of antipsychotic coprescription and associated outcome.

METHOD

Prescription charts across a large mental health trust were reviewed to identify all patients coprescribed two or more antipsychotics excluding clozapine. For those receiving antipsychotic polypharmacy for at least 6 months, electronic patient records were examined to obtain demographic data, documented reasons for initiating polypharmacy and prior prescribing information. Sequence of prescribing, clinical outcome, adverse effects and prescriber considerations to revert to monotherapy were determined.

RESULTS

In all, 38 patients had been receiving two antipsychotics excluding clozapine for longer than 6 months. In 39% of cases patients had been prescribed no or only one antipsychotic before initiation of polypharmacy while 48% had been trialled on clozapine. The most frequently documented reason for coprescribing was that residual psychotic symptoms remained with monotherapy. An improvement in psychotic symptoms was documented in 26% of patients receiving polypharmacy. Prescribers considered stopping polypharmacy in 23 patients.

CONCLUSION

Antipsychotics were coprescribed largely to improve symptoms and clinical outcome in patients with inadequate response to monotherapy. Polypharmacy was not solely reserved for patients in whom all other therapeutic options had failed. There was some evidence to suggest that patients did benefit from coprescription, albeit at the expense of an increased adverse effect burden. Prospective randomized trials of specific antipsychotic combinations are required to assess the therapeutic utility of this under-researched practice.

Predicting dopamine D₂ receptor occupancy from plasma levels of antipsychotic drugs: a systematic review and pooled analysis

Measuring dopamine D₂ receptor occupancy levels using positron emission tomography (PET) is still widely unavailable. The objective of this study was to evaluate the accuracy of predicting D2 occupancy from the antipsychotic plasma level in patients with schizophrenia. Positron emission tomographic studies that measured plasma levels of antipsychotics and their corresponding D₂ occupancy levels were identified, using MEDLINE and EMBASE (last search: March 2010). Antipsychotics that were investigated in a total of 20 subjects or more were included. All data points for each antipsychotic were fit to a one-site binding model to estimate the total plasma concentration of each antipsychotic associated with a 50% occupancy (ED₅₀) of brain D₂ receptors. The mean prediction error and the root mean squared prediction error were used to measure the predictive performance of individual D₂ receptor occupancies from plasma drug levels derived from a one-site occupancy model using an ED₅₀ value calculated for each data point. A total of 34 treatment arms from 23 studies involving 281 subjects were included. The mean (95% confidence interval) prediction errors and root squared prediction errors were as low as 0.0 (-1.8 to 1.8) and 8.9 (7.6-10.2) for risperidone (n = 98); 0.0 (-3.5 to 3.5) and 15.1 (12.9-17.3) for clozapine (n = 75); -0.1 (-1.2 to 1.2), 0.0 (-1.9 to 1.9), and 4.6 (3.5-5.8) for olanzapine (n = 42); 0.1 (-3.4 to 3.5) and 9.9 (7.3-12.5) for haloperidol (n = 35); and -0.1 (-3.3 to 3.1) and 12.3 (8.8-15.7) for ziprasidone (n = 31), respectively. These findings suggest that D₂ occupancy of antipsychotics could be estimated with a high degree of accuracy using widely available plasma levels.

Striatal D₂ receptor binding in 22q11 deletion syndrome: an [¹²³I]IBZM SPECT study

It has been hypothesised that in subjects with 22q11 deletion syndrome (22q11DS) disturbances of the dopamine (DA) system contribute to their increased risk for cognitive deficits and psychiatric problems. However, central DAergic neurotransmission in 22q11DS has not been investigated. We measured striatal D₂ receptor binding potential (D₂R BP(ND)) using (S)-(-)-3-iodo-2-hydroxy-6-methoxy-N-[(1-ethyl-2-pyrrolidinyl)methyl] benzamide-single photon emission computed tomography ([¹²³I]IBZM SPECT) in 12 adults with 22q11DS and 12 matched controls. Correlations between D₂R BP(ND) and plasma prolactin (pPRL) levels were also determined. 22q11DS subjects and controls had similar D₂R BP( ND). There was a positive correlation between D₂R BP( ND) and pPRL values in controls, but no such relation was found in 22q11DS subjects. This study suggests that a 22q11 deletion does not affect striatal DAergic neurotransmission in the living human brain. However, the disturbed relationship between D₂R BP(ND) and pPRL values suggests DAergic dysfunction at a different level. Further studies on DAergic function in extra-striatal brain regions and under challenged conditions are needed.

How have developments in molecular imaging techniques furthered schizophrenia research?

Molecular imaging techniques have led to significant advances in understanding the pathophysiology of schizophrenia and contributed to knowledge regarding potential mechanisms of action of the drugs used to treat this illness. The aim of this article is to provide a review of the major findings related to the application of molecular imaging techniques that have furthered schizophrenia research. This article focuses specifically on neuroreceptor imaging studies with PET and SPECT. After providing a brief overview of neuroreceptor imaging methodology, we consider relevant findings from studies of receptor availability, and dopamine synthesis and release. Results are discussed in the context of current hypotheses regarding neurochemical alterations in the illness. We then selectively review pharmacological occupancy studies and the role of neuroreceptor imaging in drug development for schizophrenia.

Classifying antipsychotic agents : need for new terminology

Converging data from multiple lines of research provide growing understanding of the pharmacological basis of the efficacy and tolerability of antipsychotic agents. This review highlights some of the drawbacks of the current practice of classifying antipsychotic agents into first- and second-generation agents, and argues that much of what is known about an antipsychotic agent in terms of its efficacy and tolerability can be predicted from its binding affinity at different receptors. This makes a case for a new system of classification that reflects the receptor binding affinity profiles of individual antipsychotic agents. In its quest to make a compelling case, the review provides detailed explanations for the pharmacological basis of antipsychotic efficacy, antipsychotic-induced weight gain and diabetes mellitus, cognitive effects and other adverse effects.

Metabolic and Cardiac Side Effects of Second-generation Antipsychotics: What Every Clinician Should Know

In 2007, 5 of the 7 second-generation antipsychotics were listed in the Top 200 Drugs prescribed by retail sales in the United States. Cardiovascular disease is the leading cause of natural death in individuals with schizophrenia. Second-generation antipsychotics have been implicated with metabolic and cardiovascular adverse effects, and it is important for nonpsychiatric practitioners to be familiar with the monitoring parameters recommended for these agents. This article discusses the risk of weight gain, hyperglycemia, hyperlipidemia, hyperprolactinemia, and cardiovascular concerns associated with second-generation antipsychotic agents. It also discusses the proposed mechanisms for each of these adverse effects. Furthermore, it reviews suggested monitoring parameters to help manage cardiovascular disease in this patient population, and to improve the gap that exists between mental health care and physical health care in the schizophrenic population.

Prolactin awareness: an essential consideration for physical health in schizophrenia

Elevations in serum prolactin levels (hyperprolactinaemia) are a common side effect of conventional and some atypical antipsychotic treatments. In patients with schizophrenia, the adverse effects of antipsychotic-induced hyperprolactinaemia on physical health (e.g. fertility problems, sexual dysfunction and reduced bone mineral density) are gaining attention. Accumulating evidence shows consistent 'prolactin-raising' effects of conventional antipsychotics and risperidone compared with other current atypical antipsychotics, which are more likely to have 'prolactin-sparing' properties. Prolactin-sparing antipsychotics (for example, aripiprazole and quetiapine) tend to show lower frequencies of hyperprolactinaemia-associated side effects. In recent studies, aripiprazole-treated patients have demonstrated lower prolactin levels compared with patients receiving other prolactin-sparing antipsychotics. There is a lack of robust recommendations for monitoring prolactin elevation among patients receiving antipsychotics. Decreasing the antipsychotic dose or switching to a prolactin-sparing medication are possible management options for antipsychotic-induced hyperprolactinaemia. There is a need to increase awareness and understanding of the impact of antipsychotic-induced hyperprolactinaemia on physical health in schizophrenia.

Amoxapine as an antipsychotic: comparative study versus haloperidol

It has been proposed that the lack of extrapyramidal side effects of atypical antipsychotic drugs is caused by their fast dissociation or low affinity for the D2 receptor or their concomitant high affinity for other receptors, for example, 5HT2 and D4. We noted that amoxapine, an established antidepressant, has affinity for 5HT2 and D2 receptors, and its effects in preclinical model are very similar to atypical antipsychotics. The objective of this study was to examine the antipsychotic effect and side effect profile of amoxapine versus haloperidol in a double-blind study for 6 weeks in patients with schizophrenia. A total of 54 patients with schizophrenia were titrated to the starting dose of 150 mg/d of amoxapine or 5 mg/d of haloperidol within 3 days. Clinical efficacy and side effects were monitored at baseline, and Weeks 2, 4, and 6.Forty-one patients completed 5 weeks, and 36 patients completed the 6 weeks of follow-up. Both treatment groups showed significant improvement in Positive and Negative Syndrome Scale positive (30%) and total scores (20%), without significant differences between the groups. In addition, in the amoxapine group, significant improvement was seen in the negative symptoms and the Clinical Global Impression. No significant changes were seen on Calgary Depression Scale for Schizophrenia, side effect checklists, and prolactin levels in both groups. The results suggest that amoxapine may be as effective an antipsychotic as haloperidol as predicted by its affinity for D2 and 5HT2 receptors, supporting earlier studies. However, it did not prove to have fewer extrapyramidal side effects than haloperidol, possibly because the baseline scores were very low.

Serum prolactin levels, plasma risperidone levels, polymorphism of cytochrome P450 2D6 and clinical response in patients with schizophrenia

The object of this study is to assess 1) the relationship between plasma antipsychotic drug concentration, serum prolactin levels and the clinical efficacy of risperidone, 2) the relationship between the CYP2D6 polymorphisms and metabolizing of risperidone and 3) the role of 9-hydroxyrisperidone in elevating prolactin levels. One-hundred and eighteen Chinese schizophrenia patients (40 males, 78 females, age 15-60 years) were given risperidone at dosages ranging from 2-8 mg/day for 8 weeks. Clinical efficacy was determined using the Brief Psychiatric Rating Scores (BPRS). Serum prolactin levels were assayed before and after the 8 week treatment and plasma risperidone and 9-hydroxyrisperidone levels were also measured at the end of the 8-week treatment. The results showed there was no significant correlation between the concentration of active moiety and clinical response. Risperidone treatment significantly increased serum prolactin levels. Furthermore, changes of prolactin levels were not correlated with the clinical response. For the risperidone/ 9-hydroxyrisperidone ratio, there was a statistically significant difference among the CYP2D6*1/*1, *1/*10, *10/*10 genotypes (Kruskal-Wallis test, p = 0.012). No significant differences were found in the concentration of 9-hydroxyrisperidone and active moiety among the genotypes. In addition, the concentration of 9-hydroxyrisperidone was not significantly correlated with the increase of serum prolactin. In conclusion, our study has, for the first time, produced evidence that in Chinese schizophrenic patients, the metabolism of risperidone is dependent on CYP2D6. Neither changes in serum prolactin levels nor plasma concentration of active moiety were significantly correlated with clinical efficacy of risperidone. 9-hydroxyrisperidone may not play a predominant role in elevating serum prolactin level.

Neuroreceptor imaging studies in schizophrenia

The ability of SPECT and PET to image specific biomolecules in the living brain provides a unique tool for clinical researchers. It is therefore not surprising that the use of neuroreceptor-imaging techniques has become more widespread over the past decade. This article reviews the application of these techniques to the study of schizophrenia. The design of neuroreceptor-imaging studies performed in the field of schizophrenia research can be broadly divided into two categories: (1) studies of pathophysiology and (2) studies of pharmacology. The former examines neuroreceptor and neurotransmitter parameters in individuals with schizophrenia compared to control subjects in order to provide a better understanding of the disease process. Studies of pharmacology seek to elucidate the mechanism of action for the treatments utilized in schizophrenia. This review will consider both studies of pathophysiology and pharmacology, with a discussion of the application of these techniques to drug development.

Anticholinergic use in hospitalised schizophrenic patients in Belgium

This naturalistic study aims to evaluate the influence of antipsychotic treatment on the use of anticholinergics. The observed use of anticholinergics will give an indication of the occurrence of extrapyramidal side effects (EPS) in the different antipsychotic treatment conditions. The medication use of 1215 hospitalised patients with DSM-IV 295.xx diagnosis is recorded. Four antipsychotic treatment conditions are distinguished: 1) only first generation antipsychotics (FGA): patients receive one or a combination of first generation antipsychotics, 2) a combination of high potency FGA and second generation antipsychotics (SGA), 3) a combination of low potency FGA and SGA, and 4) only SGA: patients receive one or a combination of SGA. Antipsychotic treatment significantly influences the use of anticholinergics. Anticholinergic use is highest in patients treated with high potency FGA (whether or not in combination with SGA) as compared with patients only treated with SGA and patients combining SGA with low potency FGA. The two latter groups do not significantly differ. However, there were no significant differences in the prevalence of EPS with the exception of akathisia between FGA and SGA. Thus, through the use of anticholinergics, EPS induced by FGA can be effectively reduced.

Risperidone augmentation for schizophrenia partially responsive to clozapine: a double-blind, placebo-controlled trial

RATIONALE

Risperidone augmentation of clozapine in refractory schizophrenia has theoretical but only inconsistent support from clinical trials.

OBJECTIVES

To examine if adding risperidone to stable yet symptomatic schizophrenia outpatients on optimized clozapine monotherapy improves psychopathology.

METHODS

We conducted a double-blind placebo-controlled parallel-group trial of a fixed dose of 4 mg/day risperidone added for 6 weeks in 24 outpatients with schizophrenia.

RESULTS

Subjects who received risperidone showed a non-significant decrease in PANSS total score. The PANSS disorganized thought subscale improved significantly (beta=-3.3079, p=0.047).

CONCLUSIONS

Our trial does not support the routine addition of risperidone to clozapine in refractory schizophrenia patients. However, much larger trials are needed to conclusively settle the question of added efficacy from this combination.

Clinical correlates of clozapine prescription for schizophrenia in China

AIMS

Few studies have investigated the prescription patterns of clozapine in outpatients with schizophrenia in China. It is an important issue due to clozapine's high efficacy and potentially fatal side effect profile. This study examined the use of clozapine and its correlates in China.

METHODS

Three hundred ninety-eight clinically stable outpatients with schizophrenia were randomly selected and interviewed in Hong Kong (HK) and Beijing (BJ). Assessment instruments included the Structured Clinical Interview for DSM-IV, Brief Psychiatric Rating Scale, Simpson and Angus Scale of Extrapyramidal Symptoms, Barnes Akathisia Rating Scale and the Hong Kong and Mainland China World Health Organization Quality of Life Schedule-Brief version. Assessments were performed by the same investigator in both sites.

RESULTS

Clozapine was prescribed to 15.6% of (n = 62) patients. There was a wide inter-site variation between HK and BJ. Use of clozapine was associated with age, age at onset, extrapyramidal side effects (EPS), having health insurance, use of depot and typical antipsychotic and anticholinergic drugs and benzodiazepines as well as history of suicidal attempts. On multiple logistic regression analysis, the number of hospitalizations, site (HK vs. BJ), use of typical antipsychotics, polypharmacy and co-prescription with anticholinergics were significantly associated with the prescription of clozapine. No significant differences were found between the clozapine and non-clozapine groups with regard to any of the quality of life domains.

CONCLUSION

A combination of economical and clinical factors, health policies and the characteristics of the treatment settings plays important roles in determining clozapine use. Clozapine appears to have little significant influence on quality of life in clinical stable Chinese patients with schizophrenia.

Augmentation strategies in clozapine-resistant schizophrenia

The introduction of antipsychotics in the 1950s revolutionised the treatment of schizophrenia, but it soon became apparent that a substantial number of patients demonstrated a suboptimal response to these antipsychotics. Clozapine proved to be beneficial in patients whose symptoms were treatment resistant, but it too had limitations, with as many as 40-70% of those treated with clozapine demonstrating inadequate response to this drug as well. The availability of other 'atypical' antipsychotics offers options, but clozapine appears to remain the most effective option in treatment-resistant schizophrenia. This, of course, raises the question of what to do when clozapine is only partially effective. To address the issue of treatment in patients who have demonstrated a suboptimal response to clozapine, efforts have focused on a variety of augmentation strategies, including numerous medications and electroconvulsive therapy. The current body of evidence consists largely of data from smaller open trials and case series/reports, although data from a limited number of controlled studies are now available. Not surprisingly, the evidence drawn from the former is more supportive of augmentation strategies, although the controlled trials are not without positive findings. The available information is certainly not so overwhelming as to endorse any single augmentation approach. Indeed, it argues for more controlled data and cautions us regarding the cost-benefit ratio in adopting this strategy. Over and above the added adverse effects of another treatment, there is evidence to indicate that actual clinical worsening can occur. Without compelling evidence, clinicians must resort to guiding principles. The potential benefits of augmentation cannot be ruled out, but it should be approached with caution and in a systematic fashion. Factors compromising clozapine response should first be ruled out, and any augmentation trials should be guided by existing evidence and a treatment plan that incorporates a clear understanding of target symptoms. A means of evaluating outcome effectively needs to be in place, and the trial should be circumscribed to prevent needless polypharmacy. A priori, an endpoint needs to be established and the trial discontinued unless results firmly support added benefits.

Clozapin-Augmentation mit atypischen Antipsychotika

Typical antipsychotic medications have considerably improved clinical outcome of patients suffering from schizophrenic psychoses, but up to 40% of the cases show treatment resistant symptoms. Even therapy with atypical antipsychotic drugs such as risperidone, quetiapine, olanzapine, sulpiride, amisulpride, and ziprasidone often fails to reach complete remission due to resistant, positive or negative symptoms or dose-limiting side effects. As this also holds true in the case of monotherapy with clozapine, a substance known to be effective against treatment-resistant schizophrenia, increasing numbers of patients receive atypical antipsychotic drugs in addition to clozapine. This review systematically evaluates case reports and clinical investigations on the use of clozapine combined with risperidone, olanzapine, quetiapine, sulpiride, amisulpride, or ziprasidone. Details on indication, methodology, and effects of the investigations are summarized. Only one double blind, placebo-controlled trial on the combination with sulpiride exists within a number of altogether 31 publications about 1182 treatments. Favorable effects on positive and/or negative symptoms or improvements of clozapine-induced side effects were described for every combination approach. In some cases pharmacokinetic interactions or serious unfavorable effects occurred. In conclusion it might be accepted that most of the combination therapies follow a neurobiological rational. There a major differences in the level of evidence that they are safe, tolerable and effective. We discuss criteria for the indication for augmenting clozapine therapy and the differential indication for existing alternatives. Additional randomized prospective trials are needed in order to evaluate these strategies systematically.

Tardive dyskinesia in the era of typical and atypical antipsychotics. Part 1: pathophysiology and mechanisms of induction

OBJECTIVE

Tardive dyskinesia (TD) is the principal adverse effect of long-term treatment with conventional antipsychotic agents. Several mechanisms may exist for this phenomenon. Mechanisms for the lower incidence of TD with atypical antipsychotics also remain to be fully understood. We undertook to explore and better understand these mechanisms.

METHODS

We conducted a comprehensive review of TD pathophysiology literature from January 1, 1965, to January 31, 2004, using the terms tardive dyskinesia, neuroleptics, antipsychotics, pathophysiology, and mechanisms. Additional articles were obtained by searching the bibliographies of relevant references. Articles were considered if they contributed to the current understanding of the pathophysiology of TD.

RESULTS

Current TD vulnerability models include genetic vulnerability, disease-related vulnerability, and decreased functional reserve. Mechanisms of TD induction include prolonged blockade of postsynaptic dopamine receptors, postsynaptic dopamine hypersensitivity, damage to striatal GABA interneurons, and damage of striatal cholinergic interneurons. Atypical antipsychotics may cause less TD because they have less impact on the basal ganglia and are less likely to cause postsynaptic dopamine hypersensitivity.

CONCLUSION

Although the ultimate model for TD is not yet understood, it is plausible that several of these vulnerabilities and mechanisms act together to produce TD. The lower incidence of TD with atypical antipsychotics has helped to elucidate the,mechanisms of TD.

The effect of atypical antipsychotic agents on prolactin levels in children and adolescents

This report is a review of the available literature on the effect of atypical antipsychotic agents on prolactin in children and adolescents. Fourteen reports are reviewed. Most reports (79%) have included adolescents. Three reports (21%) consisted of children only, while 7 reports (50%) included only adolescents. A total of 4 reports (29%) included both children and adolescents. The total number of subjects listed in all the reports is 276, while only 49 of the individuals on atypical neuroleptics had prolactin elevations clearly identified as outside of the normal range. The details of the reports are provided by individual atypical antipsychotic agent. Clinical implications, such as the potential impact of hyperprolactinemia on bone density, osteoporosis, gynecomastia, galactorrhea, and weight gain, are presented. Discussion of pertinent medical differential and treatment options are also reported.

Steady-state pharmacokinetics of a new antipsychotic agent perospirone and its active metabolite, and its relationship with prolactin response

The authors investigated steady-state pharmacokinetics of perospirone and its active metabolite hydroxyperospirone (ID-15036) and its prolactin response in 10 schizophrenic patients receiving 16 mg twice daily. Plasma concentrations of perospirone, hydroxyperospirone, and prolactin were monitored just before and up to 12 hours after the dosing. Thereafter, the dose was decreased to 8 mg twice daily in 8 patients, and drug concentrations were determined. The geometric means of peak concentration (Css(max)), time to Css(max) (tmax), area under the plasma concentration-time curve from 0 to 12 hours [AUC (0-12)], and elimination half-life at steady state were 8.8 ng/mL, 0.8 hours, 22.0 ng x h/mL, and 1.9 hours, respectively, for perospirone, and those of Css(max), tmax, and AUC (0-12) for hydroxyperospirone were 29.4 ng/mL, 1.1 hours, and 133.7 ng x h/mL, respectively. There were no differences in dose-normalized Css(max) or AUC (0-12) perospirone and hydroxyperospirone between 16 mg/day and 32 mg/day of perospirone. Changes in prolactin concentration from 1 to 2 hours after the dosing were parallel with drug concentrations, and almost normal ranges of prolactin concentration were observed before the morning dose despite steady state. The current study indicated that perospirone is rapidly absorbed and rapidly eliminated, which influences the prolactin response. The active metabolite hydroxyperospirone may play an important role in the antipsychotic effect because the plasma concentration of this metabolite is higher than that of the parent compound.

Atypical antipsychotic drugs and tardive dyskinesia: relevance of D2 receptor affinity

Evidence suggests atypical antipsychotic treatment is associated with a lower incidence of tardive dyskinesia (TD) than typical antipsychotic drugs, and is a potential antidyskinetic treatment. We present the case of a middle-aged woman never previously exposed to antipsychotic treatment who developed TD after 6 months of olanzapine monotherapy. Substitution of quetiapine for olanzapine alleviated her TD symptoms. The case demonstrates that atypical antipsychotic drugs have different effects in relation to TD. Potential psychopharmacological mechanisms explaining these differences are discussed, highlighting the importance of D2 receptor occupancy by atypical antipsychotic drugs for TD.

A randomized open-label study of the impact of quetiapine versus risperidone on sexual functioning

OBJECTIVE

To compare sexual functioning in patients treated with quetiapine or risperidone.

METHODS

This open-label study included patients with schizophrenia or a related psychotic illness who were randomized to quetiapine (200-1200 mg/d) or risperidone (1-6 mg/d) for 6 weeks. Sexual dysfunction was assessed by a semistructured interview, the Antipsychotics and Sexual Functioning Questionnaire (ASFQ), based upon the Utvalg for Kliniske Undersogelser (UKU).

RESULTS

Four of 25 quetiapine-treated patients (16%) and 12 of 24 risperidone-treated patients (50%) reported sexual dysfunction (chi 2 = 6.4; df = 1; P = 0.006) on the ASFQ. Six patients (11.7%; 4 on risperidone, 2 on quetiapine) spontaneously reported sexual dysfunction. The mean+/-SD dose was 580+/-224 mg/d for quetiapine and 3.2 +/- 1.3 mg/d for risperidone. Mean +/- SD prolactin levels in quetiapine- and risperidone-treated patients were 13.8 +/- 17.9 and 57.7 +/- 39.7 ng/mL, respectively.

CONCLUSION

Sexual dysfunction was less common in patients treated with quetiapine than with risperidone. Direct questioning about sexual functioning is necessary to avoid underestimating the frequency of sexual side effects in patients with schizophrenia and related psychotic disorders.

Antipsychotic combination therapy in schizophrenia. A review of efficacy and risks of current combinations

OBJECTIVE

To review the literature on efficacy and risks of combining antipsychotics (atypical with atypical or conventional) and suggest a rationale and strategies for future clinical trials.

METHOD

A computerized Medline search supplemented by an examination of cross-references and reviews was performed.

RESULTS

Empirical evidence for the efficacy of combining antipsychotics is too limited to draw firm conclusions. The practice of augmenting clozapine with more 'tightly bound' D2 receptor antagonists as exemplified by risperidone augmentation of clozapine has some empirical and theoretical support. The risks of augmentation strategies have not been studied systematically. No study has examined the economic impact of combination treatment.

CONCLUSION

Further trials of antipsychotic combination therapies are needed before this currently unsupported practice can be recommended. Rationales for combination treatment include a broadening of the range of receptor activity or an increase in D2 receptor occupancy with certain atypical agents. Trial methodology needs to take into account subject characteristics, duration of treatment, optimization of monotherapy comparators, and appropriate outcome measures.

The differential effects of atypical antipsychotics on prolactin elevation are explained by their differential blood-brain disposition: a pharmacological analysis in rats

All atypical antipsychotics avoid extrapyramidal side-effects yet differ in their propensity to cause other side-effects, like prolactin elevation. We proposed that the atypical antipsychotics with a propensity for prolactin elevation would show a higher pituitary versus striatal D2 receptor occupancy. To investigate this hypothesis, we tested four atypical antipsychotics, two that are commonly associated with prolactin elevation (amisulpride and risperidone) and two that are less frequently associated (quetiapine and olanzapine). In particular, we calculated their ED(50) values to increase plasma prolactin and block peripheral pituitary D2 receptors to their ED(50) values to antagonize apomorphine-induced stereotypy and occupy central striatal D2 receptors. All antipsychotics dose dependently increased prolactin levels and antagonized apomorphine-induced stereotypy. However, the central to peripheral potency (ED(50) for apomorphine antagonism to ED(50) for prolactin elevation) differed remarkably across these drugs: amisulpride (21764), risperidone (14), quetiapine (10), and olanzapine (1.7). Compounds displaying a higher peripheral potency brought about higher prolactin levels for a given level of functional central antagonism. This dissociation between central and peripheral effects was explained by the differential occupancy of D2 receptors in the striatum versus in the pituitary [ratio of striatal/pituitary ED(50) values (milligram per kilogram) for D2 occupancy): amisulpride (17/0.026 = 654), risperidone (0.89/0.081 = 14), quetiapine (24/4.1 = 6), olanzapine (0.30/0.43 = 0.7). These results indicate that dissociation between central and peripheral D2 receptor occupancy is a major determinant of the degree of prolactin elevation observed at therapeutic doses.

Increasing D2 affinity results in the loss of clozapine's atypical antipsychotic action

Typical antipsychotics (haloperidol) give rise to severe motor side-effects while atypical antipsychotics like clozapine do not. Action at several neurotransmitter receptors have been implicated. To identify the critical mechanisms involved we synthesized an 8-C1 isomer of clozapine which showed an equivalent affinity to clozapine on multiple receptors (5-HT1A, 5-HT2, D1, D4, M1) but differed in having a 10-fold higher affinity at the dopamine D2/3 receptor. When tested in a series of animal models indicative of the typical/atypical distinction (catalepsy, striatal gene-induction, prolactin elevation) isoclozapine lost atypical properties and behaved like a typical antipsychotic. Simultaneous in vivo receptor occupancy studies confirmed that alterations in D2 receptor occupancy were most closely related to loss of atypicality by clozapine's isomer isoclozapine. The implications for the design of future antipsychotics is discussed.

Risperidone-induced increase in serum prolactin is correlated with positive symptom improvement in chronic schizophrenia

The elevation in serum prolactin (PRL) concentration in schizophrenic patients treated with typical antipsychotic drugs is well documented. Recently, increased prolactin levels have been reported in patients taking risperidone. The purpose of this study was to explore the effect of the atypical antipsychotic drug risperidone on serum prolactin, and to investigate the relationship between the change in PRL and the therapeutic outcome. In this study, 30 male inpatients with a diagnosis of chronic schizophrenia (DSM-III-R) were assigned to 12 weeks of treatment with risperidone after a 2-week washout period. The risperidone dose was fixed at 6 mg/day. Clinical efficacy was determined using the Positive and Negative Syndrome Scale (PANSS). Serum PRL was assayed in serum by radioimmunometric assay in schizophrenic patients before and after 12-week treatment, as compared to 30 age-matched normal male subjects. The results showed that risperidone treatment significantly increased the serum PRL. A significant and positive relationship between the change in PRL at pre- and post-treatment and the reduction rate of PANSS positive subscore was observed. Risperidone treatment significantly increased the serum PRL levels of schizophrenic patients. There was a close relationship between the improvement in positive symptoms and the change of serum PRL level before and after risperidone treatment. The serum PRL levels at baseline could be used to predict the responses of schizophrenic patients to risperidone.

Minimal effects of JL 13, a pyridobenzoxazepine derivative with an antipsychotic potential, on circulating prolactin levels in male rats

Antipsychotic therapy is frequently associated with several side effects such as hyperprolactinemia. The influence of a putative antipsychotic JL 13 on prolactin release was assessed after intraperitoneal injection in gentled male rats in comparison with clozapine and haloperidol. A total of 30 or 150 min after administration, whole blood was collected for preparing serum samples. Prolactin was quantified by radioimmunoassay method. At 30 min, JL 13 like clozapine, increased prolactin concentration only at the higher dose (30 mg/kg) while haloperidol at both tested doses induced a dramatic increase of prolactin concentration. At 150 min after injection, only haloperidol (0.3 mg/kg) significantly increased serum prolactin level. This minimal effect on prolactinemia reinforces the similarity of clozapine and JL 13 regarding the atypical antipsychotic profile.

Choosing the right dose of antipsychotics in schizophrenia: lessons from neuroimaging studies

Despite vast clinical experience with antipsychotics, there is no broad consensus on the doses of these substances that should be administered. Currently, most antipsychotics are administered empirically according to clinical dose-finding studies, in which arbitrarily selected doses were tested to find the "most efficient" dose range in a patient population, with no regard for the molecular effects of the tested drug. Brain imaging studies using nuclear medical techniques, such as positron emission tomography (PET) or single photon emission computed tomography (SPECT), can now provide a rationale for doses, directly derived from the central effects of the drugs on neurotransmitter receptors measured in vivo. PET results indicate that occupancy of at least 65% of dopamine D(2) receptors is needed for clinical response to antipsychotics, and that occupancy rates exceeding 72 and 78% are associated with a high risk for elevation of prolactin levels and motor adverse effects, respectively. For example, clinical studies with haloperidol do not point to an advantage of dosages exceeding 5 mg/day. The relevance of D(2) receptor occupancy for drug administration is also borne out by studies relating the effects of antipsychotics to their D(2) receptor occupancy in relevant animal models. Taken together, neuroimaging and clinical studies, as well as animal models, provide a rationale for the use of relatively low doses of typical antipsychotics and equivalent doses of novel antipsychotics. The lower risk of adverse effects with appropriate doses of antipsychotics may further enhance compliance and outcome. This seems to be particularly important in individuals experiencing a first episode of schizophrenia, as they appear to be especially responsive to pharmacotherapy and quite sensitive to adverse effects.