Monthly administration of long-acting injectable risperidone and striatal dopamine D2 receptor occupancy for the management of schizophrenia

Optimisation of pharmacotherapy in psychiatry through therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests: Focus on antipsychotics

BACKGROUND

For psychotic disorders (i.e. schizophrenia), pharmacotherapy plays a key role in controlling acute and long-term symptoms. To find the optimal individual dose and dosage strategy, specialised tools are used. Three tools have been proven useful to personalise drug treatments: therapeutic drug monitoring (TDM) of drug levels, pharmacogenetic testing (PG), and molecular neuroimaging.

METHODS

In these Guidelines, we provide an in-depth review of pharmacokinetics, pharmacodynamics, and pharmacogenetics for 45 antipsychotics. Over 30 international experts in psychiatry selected studies that have measured drug concentrations in the blood (TDM), gene polymorphisms of enzymes involved in drug metabolism, or receptor/transporter occupancies in the brain (positron emission tomography (PET)).

RESULTS

Study results strongly support the use of TDM and the cytochrome P450 (CYP) genotyping and/or phenotyping to guide drug therapies. Evidence-based target ranges are available for titrating drug doses that are often supported by PET findings.

CONCLUSION

All three tools discussed in these Guidelines are essential for drug treatment. TDM goes well beyond typical indications such as unclear compliance and polypharmacy. Despite its enormous potential to optimise treatment effects, minimise side effects and ultimately reduce the global burden of diseases, personalised drug treatment has not yet become the standard of care in psychiatry.

Does Slow and Steady Win the Race? Rates of Antipsychotic Discontinuation, Antipsychotic Dose, and Risk of Psychotic Relapse

BACKGROUND

Antipsychotics are recommended for prevention of relapse in schizophrenia. It is unclear whether increased risk of relapse following antipsychotic discontinuation is predominantly associated with an absolute magnitude of dose reduction or rate of antipsychotic reduction. Establishing the responsible mechanism is important because prolonged withdrawal schedules have been suggested to reduce risk of relapse.

STUDY DESIGN

Individual patient data from antipsychotic discontinuation studies were obtained. We estimated the occupancy of receptors over time using half-lives and median effective dose ED50 values obtained from pharmacokinetic and receptor occupancy studies. Hazard ratios for relapse events were calculated using Cox proportional hazards models to assess the influence of formulation (oral, 1-monthly, and 3-monthly injections). The change in hazard ratio over time was estimated, and the effect of time-varying covariates was calculated, including rate of occupancy reduction and absolute receptor occupancy.

STUDY RESULTS

Five studies including 1388 participants with schizophrenia were identified (k = 2: oral, k = 2: 1-monthly injection, k = 1: 3-monthly injection). Withdrawal of long-acting injectable medication did not lead to a lower hazard ratio compared with withdrawal of oral medication, and this included the period immediately following randomization. Hazard ratios were not associated with the rate of decline of receptor occupancy; however, they were associated with reduced absolute occupancy in trials of long-acting injections (P = .038).

CONCLUSIONS

Antipsychotic discontinuation is associated with an increased risk of psychotic relapse, related to receptor occupancy. Although relapse does not appear to be related to the rate of discontinuation, gradual discontinuation strategies may allow for easier antipsychotic reinstatement in case of symptomatic worsening.

Update Lessons from Positron Emission Tomography Imaging Part I: A Systematic Critical Review on Therapeutic Plasma Concentrations of Antipsychotics

BACKGROUND

Positron emission tomography (PET) and single photon emission tomography (SPECT) of molecular drug targets (neuroreceptors and transporters) provide essential information for therapeutic drug monitoring-guided antipsychotic drug therapy. The optimal therapeutic windows for D 2 antagonists and partial agonists, as well as their proposed target ranges, are discussed based on an up-to-date literature search.

METHODS

This part I of II presents an overview of molecular neuroimaging studies in humans and primates involving the target engagement of amisulpride, haloperidol, clozapine, aripiprazole, olanzapine, quetiapine, risperidone, cariprazine, and ziprasidone. The systemic review particularly focused on dopamine D 2 -like and 5-HT 2A receptors. Target concentration ranges were estimated based on receptor occupancy ranges that relate to clinical effects or side effects (ie, extrapyramidal side effects). In addition, findings for other relevant receptor systems were included to further enrich the discussion.

RESULTS

The reported reference ranges for aripiprazole and clozapine align closely with findings from PET studies. Conversely, for haloperidol, risperidone, and olanzapine, the PET studies indicate that a lowering of the previously published upper limits would be necessary to decrease the risk of extrapyramidal side effect.

CONCLUSIONS

Molecular neuroimaging studies serve as a strong tool for defining target ranges for antipsychotic drug treatment and directing therapeutic drug monitoring.

The Relation between the Plasma Concentrations of Long-Acting Atypical Antipsychotics and Clinical Effectiveness in Patients Affected by Schizophrenia or Schizoaffective Disorder: A Comprehensive Overview

Atypical antipsychotic depot medications are currently recommended for patients with schizophrenia (SCZ) to prevent relapse and ameliorate the long-term prognosis of these patients. This review critically summarizes the available data about the association between the plasma concentrations of long-acting Second- Generation Antipsychotics (SGAs) and the clinical effectiveness of these compounds in patients affected by SCZ or schizoaffective disorder. Our question is if the measurement of these concentrations can be helpful for clinicians in predicting treatment response and clinical stabilization of patients. Bibliographic research on the main databases was performed, and 13 studies were finally included in this review. Contrasting results were found between plasma concentrations of long-acting injectable (LAI) risperidone and clinical amelioration according to rating scale scores. Data are too scanty to draw conclusions for olanzapine and paliperidone. In contrast, despite small sample sizes, data are quite concordant in showing a relation between long-acting SGA plasma concentrations and D2 receptor occupancy. Despite the preliminary encouraging results, particularly for D2 receptor occupancy, future research with larger samples will have to confirm the clinical usefulness of measuring LAI SGA plasma concentrations to predict the clinical response of patients affected by severe mental conditions such as SCZ.

Therapeutic Drug Monitoring of Long-Acting Injectable Antipsychotic Drugs

BACKGROUND

The use of therapeutic drug monitoring (TDM) to guide treatment with long-acting injectable (LAI) antipsychotics, which are increasingly prescribed, remains a matter of debate. The aim of this review was to provide a practical framework for the integration of TDM when switching from an oral formulation to the LAI counterpart, and in maintenance treatment.

METHODS

The authors critically reviewed 3 types of data: (1) positron emission tomography data evaluating dopamine (D2/D3) receptor occupancy related to antipsychotic concentrations in serum or plasma; D2/D3 receptors are embraced as target sites in the brain for antipsychotic efficacy and tolerability, (2) pharmacokinetic studies evaluating the switch from oral to LAI antipsychotics, and (3) pharmacokinetic data for LAI formulations. Based on these data, indications for TDM and therapeutic reference ranges were considered for LAI antipsychotics.

RESULTS

Antipsychotic concentrations in blood exhibited interindividual variability not only under oral but also under LAI formulations because these concentrations are affected by demographic characteristics such as age and sex, genetic peculiarities, and clinical variables, including comedications and comorbidities. Reported data combined with positron emission tomography evidence indicated a trend toward lower concentrations under LAI administration than under oral medications. However, the available evidence is insufficient to recommend LAI-specific therapeutic reference ranges.

CONCLUSIONS

Although TDM evidence for newer LAI formulations is limited, this review suggests the use of TDM when switching an antipsychotic from oral to its LAI formulation. The application of TDM practice is more accurate for dose selection than the use of dose equivalents as it accounts more precisely for individual characteristics.

Continuous versus extended antipsychotic dosing in schizophrenia: Less is more

Antipsychotic drugs temper psychotic symptoms by interacting with dopamine D2 receptors to reduce dopamine neurotransmission. Currently, the standard of care involves antipsychotic treatment protocols that achieve steady-state levels of medication. Maintaining patients on continuous treatment is thought to be necessary to keep them stabilised. However, continuous antipsychotic exposure increases the risk of adverse effects over time. These effects include metabolic and cardiovascular disorders, extrapyramidal complications, and dopamine receptor supersensitivity, the latter of which could potentially promote both treatment tolerance and psychosis relapse. In the present review, we describe evidence showing that continuous exposure to antipsychotic drugs can not only worsen long-term outcome, but-past acute phase treatment-it is also unnecessary to effectively manage schizophrenia symptoms. We also describe evidence that regular but extended dosing, allowing predictable periods of lower antipsychotic levels/D2 occupancy, is both safe and effective in patients, and it greatly reduces drug exposure overall. Studies in laboratory animals show that compared to continuous antipsychotic exposure, regular but extended dosing actually has superior antipsychotic-like efficacy, and it also substantially reduces the likelihood of both motor side effects and dopamine receptor supersensitivity. We propose that regular, but extended dosing should be considered in the long-term treatment of people with schizophrenia, because the available evidence suggests it can be just as effective as continuous treatment, while decreasing overall drug exposure and potentially reducing harmful side effects.

Gap between patients with schizophrenia and their psychiatrists on the needs to psychopharmacological treatment: A cross-sectional study

Aim

Psychopharmacological treatment is indispensable in patients with schizophrenia but data on needs, preferences, and complaints about their medications are limited. Moreover, there has been no study to assess the degree of awareness of their psychiatrists (gap in needs) regarding these issues.

Methods

Ninety‐seven Japanese patients with schizophrenia (ICD‐10) were asked to fill in the questionnaire consisting of multiple‐choice questions regarding (a) their needs and complaints about psychopharmacological treatment that they were receiving, and (b) their preference of dosage form, dosing frequency, and timing of dosing. Additionally, their psychiatrists in charge were asked to predict their patients’ response to the above questions.

Results

Both the most frequently endorsed need and complaints about the current psychopharmacological treatment were “nothing in particular” (n = 14, 16.7% and n = 17, 20.2%); merely 23.1% and 15.4% of their psychiatrists correctly predicted these responses, respectively. “Once a day” (n = 56, 65.1%), “at bedtime” (n = 53, 61.6%), and “tablet” (n = 51, 59.3%) were the patients’ most favorite dosing frequency, timing, and dosage form, respectively; 59.8% (n = 49), 54.9% (n = 45), and 64.6% (n = 53) of their psychiatrists predicted them.

Conclusions

These findings suggest that there is substantial room for improvement on the side of psychiatrists to capture their patients’ needs and complaints about psychopharmacological treatment.

Model-Guided Antipsychotic Dose Reduction in Schizophrenia: A Pilot, Single-Blind Randomized Controlled Trial

PURPOSE/BACKGROUND

Patients with schizophrenia as well as their psychiatrists are hesitant to reduce the antipsychotic dose in fear of relapse. To overcome such dilemmas, we developed models to individually calculate an oral dose that corresponds to a given target dopamine D2 receptor occupancy.

METHODS/PROCEDURES

In this pilot, 52-week single-blind randomized controlled trial, 35 clinically stable patients with schizophrenia receiving either risperidone or olanzapine monotherapy were randomly assigned to dose reduction (n = 17) or dose maintenance group (n = 18). In the former group, baseline doses were reduced to the doses corresponding to 65% D2 occupancy (the lower end of therapeutic window) at trough that were calculated from randomly collected plasma concentrations using our models.

FINDINGS/RESULTS

In the dose reduction group, doses of risperidone and olanzapine were decreased from 4.2 ± 1.9 to 1.4 ± 0.4 and 12.8 ± 3.9 to 6.7 ± 1.8 mg/d, whereas the doses in the dose maintenance group were 4.3 ± 1.9 and 15.8 ± 4.6 mg/d, respectively. Twelve subjects (70.5%) and 13 subjects (72.2%) in the dose reduction and dose maintenance groups completed the study (P = 0.604), whereas 3 subjects (18.8%) and none dropped out because of clinical worsening in the dose reduction and dose maintenance groups, respectively. There were not significant differences in score changes in Positive and Negative Syndrome Scale between the 2 groups but in Positive subscale scores in the Clinical Global Impression-Schizophrenia (0.4 ± 0.7 in the dose reduction group vs -0.1 ± 0.7 in the dose maintenance group, P = 0.029).

IMPLICATIONS/CONCLUSIONS

Although our model-guided dose reduction strategy was found to be comparable with no-dose change in terms of dropout rates, safety issues have to be further examined.

Achieving the Lowest Effective Antipsychotic Dose for Patients with Remitted Psychosis: A Proposed Guided Dose-Reduction Algorithm

Continuing antipsychotic treatment in patients with schizophrenia under clinical remission remains controversial. Even though the mainstream opinion declares an outweighed balance against medication discontinuation, recent reviews and critiques suggest that some patients may remain symptom free and well functioning after stopping antipsychotics, but few predictors can identify who can try medication discontinuation, whilst no guidelines exist for reducing medication to reach the lowest effective dose safely. Analyzing the findings from studies employing different methodologies, adopting evidence from pharmacodynamic research, and observing dose reduction in stable patients, as well as taking inspiration from the metaphor of the Cantor set in natural philosophy, we introduce an alternative solution and propose a guided dose-reduction algorithm that follows a set of clear precautions and instructions. The algorithm recommends only a fraction (no more than 25%) of the dosage to be reduced at a time, with at least a 6-month stabilization period required before reducing another 25% of the dose. Patients are empowered to actively participate in decision making when they are ready for further dose tapering, or should they retreat to a previous dosage if warning signs of a relapse re-emerge. An intermittent or irregular dosing schedule can be used to adapt this algorithm to real-world practice. Our preliminary findings suggest that patients with remitted psychosis can do well along this path. We anticipate that this approach can help optimize the risk-benefit ratio and instill a hope in patients with schizophrenia that they can maintain in stable remission under a lower antipsychotic dose without an increased risk of relapse.

Switching Antipsychotics to Blonanserin in Patients with Schizophrenia: An Open-label, Prospective, Multicenter Study

Objective

This study was performed to investigate the efficacy and tolerability of blonanserin in schizophrenic patients who were previously treated with other antipsychotics but, due to insufficient response, were switched to blonanserin.

Methods

A total of 52 patients with schizophrenia who were unresponsive to treatment with antipsychotic monotherapy or combination therapy were recruited into this 12-week, open-label, prospective, multicenter study. Patients were switched to blonanserin from their existing antipsychotics over a maximum 2-week tapering-off period. Efficacy was primarily evaluated using the 18-item Brief Psychiatric Rating Scale (BPRS). Assessments were performed at baseline, and at weeks 1, 2, 4, 8, and 12.

Results

Switching to blonanserin resulted in a significant decrease in the mean total score on the BPRS from baseline (56.8 ± 9.4) to week 12 (42.1 ± 13.8, p < 0.001). The most common adverse events were extrapyramidal symptoms (n = 12, 23.1%), insomnia (n = 10, 19.2%), and emotional arousal (n = 6, 11.5%). Overweight or obese patients (body mass index ≥ 23 kg/m², n = 33) who switched to blonanserin exhibited significant weight loss from 75.2 ± 9.3 kg at baseline to 73.5 ± 9.2 kg at week 12 (p = 0.006). The total cholesterol (baseline, 236.1 ± 47.6 mg/dl; endpoint [week 12], 209.9 ± 28.0 mg/dl; p = 0.005) and prolactin levels (baseline, 80.0 ± 85.2 ng/ml; endpoint [week 12], 63.2 ± 88.9 ng/ml; p = 0.003) were also significantly improved in patients with hypercholesterolemia or hyperprolactinemia.

Conclusion

The results of the present study suggest that switching to blonanserin may be an effective strategy for schizophrenic patients unresponsive to other antipsychotic treatments.

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.

Plasma levels and estimated dopamine D2 receptor occupancy of long-acting injectable risperidone during maintenance treatment of schizophrenia: a 3-year follow-up study

INTRODUCTION

Dopamine D₂ receptor occupancy levels needed for the maintenance treatment of schizophrenia remain to be elucidated. We examined 3-year clinical outcomes of patients with schizophrenia who received long-acting injectable risperidone (LAI risperidone) at baseline and investigated their dopamine D₂ receptor occupancy levels, estimated from plasma drug concentrations.

METHODS

A chart review of 52 outpatients with schizophrenia who participated in the original cross-sectional study was conducted to examine their 3-year clinical outcomes between April and September 2015. Patients who continued outpatient treatment with LAI risperidone without any usage of concomitant chlorpromazine equivalent antipsychotic dosage at >200 mg/day for the 3-year period were asked to participate in the follow-up assessments that included the Brief Psychiatric Rating Scale (BPRS) and estimated dopamine D₂ receptor occupancy levels at trough, using plasma concentrations of risperidone plus 9-hydroxyrisperidone. Data were compared with the same patients collected 3 years earlier.

RESULTS

Among the original 52 participants, 14 participants (27 %) continued outpatient treatment with LAI risperidone. Ten participants (19 %) provided plasma samples; mean ± SD measured trough concentration of risperidone plus 9-hydroxyrisperidone significantly increased from 22.9 ± 15.6 to 31.8 ± 17.5 ng/mL (P = 0.02). Estimated dopamine D₂ receptor occupancy numerically increased from 63.0 ± 10.9 to 69.0 ± 11.0 % (P = 0.12). A significant worsening was observed in the BPRS total score among these patients (mean ± SD, 34.3 ± 12.7 to 46.5 ± 16.9, P = 0.003).

CONCLUSION

Paradoxically, the increased plasma concentration was found to be associated with a significant worsening of the clinical outcome. More investigations are indicated to shed further light on optimal levels of D₂ blockade in the maintenance treatment of schizophrenia.

Antipsychotic dose in maintenance treatment of schizophrenia: A retrospective study

The dose of antipsychotic required for acute phase treatment of schizophrenia is well established, but there is no consensus on dose required for maintenance phase. Current guidelines do not provide definitive recommendations on the dose of antipsychotics needed in the maintenance treatment of schizophrenia, possibly due to limited research. In this retrospective study, minimum antipsychotic dose prescribed in maintenance treatment of schizophrenia in a real life situation was examined. Schizophrenia patients having Clinical Global Impression - Severity (CGI-S)≤3 for at-least six months during the maintenance phase treatment were included (n=163). The medical records of these patients were reviewed and the antipsychotic dose prescribed for acute and maintenance phase treatment was recorded. The mean antipsychotic dose used during maintenance treatment was approximately 30% lower than the dose used during acute phase. Importantly, about 40% of the subjects maintained well with a dose lesser than the recommended therapeutic range. Earlier age at onset and longer duration of illness were associated with higher antipsychotic dose requirement during the maintenance phase treatment. These findings could have important clinical implications if replicated in systematic prospective studies.

Challenging the need for sustained blockade of dopamine D₂ receptor estimated from antipsychotic plasma levels in the maintenance treatment of schizophrenia: A single-blind, randomized, controlled study

OBJECTIVE

Blockade of dopamine D₂ receptors with antipsychotics above 65% is associated with optimal chance of clinical response although recent data suggest a lower threshold for the maintenance treatment of schizophrenia. The objective of this study was to prospectively examine whether such continuous high blockade would be necessary for maintenance treatment.

METHOD

In this single-blind, 52-week, randomized controlled trial, clinically stable patients with schizophrenia receiving risperidone or olanzapine were randomly assigned to the continuous D₂ blockade (i.e. an estimated trough D2 blockade of >65%) or non-continuous blockade group (i.e. an estimated peak level of >65% with an estimated trough level of <65%). Oral doses corresponding to the assigned blockade levels were estimated from random plasma drug concentrations, using the models we developed; antipsychotic doses were then adjusted accordingly. Psychopathology and side effects were assessed at baseline and one year with the Positive and Negative Syndrome Scale (PANSS), Simpson-Angus Scale (SAS), and Abnormal Involuntary Movement Scale (AIMS).

RESULTS

Sixty-eight subjects (34 in each group) were enrolled. Twenty-six (76.5%) and thirty-one (91.2%) subjects completed the study in the continuous and non-continuous blockade groups, respectively, without any significant group difference. No significant differences were found on any of the assessment scales between the two groups. The degree of dosage change was small in both groups.

CONCLUSION

These results offer support that the threshold for D₂ receptor blockade in the maintenance treatment can be lower than 65%. However, these preliminary findings have to be confirmed through double-blind, larger scale trials with longer follow-up periods.

Dose and dosing frequency of long-acting injectable antipsychotics: a systematic review of PET and SPECT data and clinical implications

Brain imaging data of antipsychotics have mainly been derived from oral antipsychotic drugs, which hampers our understanding of the requirement of dose/dosing frequency of long-acting injectable (LAI) antipsychotics for the maintenance treatment of schizophrenia. A systematic literature search was performed to identify positron emission tomography (PET) and single-photon emission computed tomography (SPECT) studies that assessed dopamine D2 receptor occupancy levels with LAI antipsychotic drugs in humans, using PubMed, EMBASE, and PsycINFO (last search, February 2013). Twenty studies (15 PET and 5 SPECT studies) were identified. The most investigated drug in these PET and SPECT studies was haloperidol decanoate (44 subjects; 11 studies), followed by risperidone LAI (24 subjects; 3 studies), olanzapine pamoate (14 subject; 1 study), and fluphenazine decanoate (12 subjects; 3 studies). The data have demonstrated high and continuous D2 receptor blockade with LAIs; the effects of LAI first-generation antipsychotics on the central nervous system may persist for several months. The prospective and cross-sectional studies showed that continuous dopamine D2 receptor blockade above 65% (ie, the lower end of the established therapeutic window for the acute phase treatment) was not always necessary for maintenance treatment for at least some of the patients. In conclusion, because of the limited brain imaging data on LAI antipsychotics, we still do not know the best way to dose them. Still, the currently available brain imaging data raises a possibility that the dosing interval of LAI antipsychotics may be extended beyond the currently indicated range in some patients.

[Long-acting injectable antipsychotics. Overview and advice for daily routine care]

Recent investigations have demonstrated a significant reduction of relapse and hospitalization rates associated with the use of long-acting injectable antipsychotics (LAIs) in the treatment of schizophrenia. There are only marginal differences in the effectiveness of different specific LAIs. Furthermore, LAIs are comparable to the oral equivalents with respect to effectiveness and side effects. The occurrence of extrapyramidal motor disorders (EPD) is less frequent in second generation (SG) LAIs than in first generation (FG) LAIs. Moreover, specific characteristics of some substances should be considered: In SG-LAIs immediate onset of action is only applicable for olanzapine and paliperidone and FG-LAIs should always be given as a test dose first to assure a general tolerance. All LAIs have a high variability of plasma levels which complicates the dose titration. Last but not least, current research concerning long-term consequences of continuous treatment with antipsychotics and the potentially poorer response to antipsychotics should be considered.

Presynaptic dopaminergic function: implications for understanding treatment response in psychosis

All current antipsychotic drugs block dopamine (DA) receptors, but the nature of the DA dysfunction in schizophrenia has not been clear. However, consistent evidence now shows that presynaptic dopaminergic function is altered in schizophrenia, specifically in terms of increased DA synthesis capacity, baseline synaptic DA levels, and DA release. Furthermore, presynaptic dopaminergic function is already elevated in prodromal patients who later developed the disorder. Currently available antipsychotics act on postsynaptic receptors, not targeting presynaptic DA abnormalities. This has implications for understanding response and developing new treatments. The lack of normalization of the abnormal presynaptic function could explain why discontinuation is likely to lead to relapse, because the major dopaminergic function persists, meaning that once treatment stops there is nothing to oppose the dysregulated dopamine function reinstating symptoms. Furthermore, it suggests that drugs that target presynaptic dopaminergic function may constitute new treatment possibilities for schizophrenic patients, in particular, for those in whom antipsychotics are poorly effective. In addition, the longitudinal changes with the onset of psychosis indicate the potential to target a defined dynamic neurochemical abnormality to prevent the onset of psychosis.

Antipsychotic dosing: found in translation

In the field of schizophrenia research, as in other areas of psychiatry, there is a sense of frustration that greater advances have not been made over the years, calling into question existing research strategies. Arguably, many purported gains claimed by research have been "lost in translation," resulting in limited impact on diagnosis and treatment in the clinical setting. There are exceptions; for example, we would argue that different lines of preclinical and clinical research have substantially altered how we look at antipsychotic dosing. While this story remains a work in progress, advances "found in translation" have played an important role. Detailing these changes, the present paper speaks to a body of evidence that has already shifted clinical practice and raises questions that may further alter the manner in which antipsychotics have been administered over the last 6 decades.

Intermittent drug techniques for schizophrenia

BACKGROUND

Antipsychotic medication is considered the mainstay of treatment for schizophrenia and is generally regarded as highly effective, especially in controlling positive symptoms. However, long-term antipsychotic exposure has been associated with a range of adverse effects, including extra-pyramidal symptoms (EPS), neuroleptic malignant syndrome (NMS), tardive dyskinesia and death. Intermittent drug techniques refers to the 'use of medication only during periods of incipient relapse or symptom exacerbation rather than continuously'. The aim is to reduce the risk of typical adverse effects of antipsychotics by 'reducing long-term medication exposure for patients who are receiving maintenance treatment while limiting the risk of relapse', with a further goal of improving social functioning resulting from the reduction of antipsychotic-induced side effects

OBJECTIVES

To review the effects of different intermittent drug techniques compared with maintenance treatment in people with schizophrenia or related disorders.

SEARCH METHODS

We searched The Cochrane Schizophrenia Group Trials Register (April 2012) and supplemented this by contacting relevant study authors, handsearching relevant intermittent drug treatment articles and manually searching reference lists.

SELECTION CRITERIA

All randomised controlled trials (RCTs) that compared intermittent drug techniques with standard maintenance therapy for people with schizophrenia. Primary outcomes of interest were relapse and hospitalisation.

DATA COLLECTION AND ANALYSIS

At least two review authors selected trials, assessed quality and extracted data. We calculated risk ratios (RR) and 95% confidence intervals (CI) of homogeneous dichotomous data and estimated the 95% confidence interval (CI) around this. For non-skewed continuous endpoint data extracted from valid scales, we estimated mean difference (MD) between groups with a 95% CI. Where data displayed heterogeneity, these were analysed using a random-effects model. Skewed data are presented in tables. We assessed overall quality for clinically important outcomes using the GRADE approach.

MAIN RESULTS

Of 241 records retrieved by the search, 17 trials conducted between 1961 and 2011, involving 2252 participants with follow-up from six weeks to two years, were included. Homogenous data demonstrated that instances of relapse were significantly higher in people receiving any intermittent drug treatment in the long term (n = 436, 7 RCTs, RR 2.46, 95% CI 1.70 to 3.54, moderate quality evidence). Intermittent treatment was shown to be more effective than placebo, however, and demonstrated that significantly less people receiving intermittent antipsychotics experienced full relapse by medium term (n = 290, 2 RCTs, RR 0.37, 95% CI 0.24 to 0.58, very low quality evidence). Hospitalisation rates were higher for people receiving any intermittent drug treatment by long term (n = 626, 5 RCTs, RR 1.65, 95% CI 1.33 to 2.06, moderate quality evidence). Results demonstrated little difference in instances of tardive dyskinesia in groups with any intermittent drug technique versus maintenance therapy, with equivocal results (displaying slight heterogeneity) at long term (n = 165, 4 RCTs, RR 1.15, 95% CI 0.58 to 2.30, low quality evidence).

AUTHORS' CONCLUSIONS

Results of this review support the existing evidence that intermittent antipsychotic treatment is not as effective as continuous, maintained antipsychotic therapy in preventing relapse in people with schizophrenia. More research is needed to assess any potential benefits or harm of intermittent treatment regarding adverse effects typically associated with maintained antipsychotic treatment, as well as any cost-effectiveness of this experimental treatment.

Antipsychotics, dopamine D₂ receptor occupancy and clinical improvement in schizophrenia: a meta-analysis

OBJECTIVE

Treatment of schizophrenia (SCZ) was revolutionized with the development of the antipsychotic medications. Although imaging studies have linked antipsychotic D₂ receptor occupancy and clinical response in SCZ, heterogeneity between cohorts and methods has made it challenging to generalize findings across studies. The main objective of this meta-analysis was to analyze the relationship between in vivo estimation of typical and atypical antipsychotic D₂ receptor occupancy and treatment response in SCZ.

METHODS

Using the keywords "dopamine D₂ receptor occupancy," "schizophrenia," "PET/SPECT" and "antipsychotics," and further refining our search to journal articles with information on % striatal D₂ occupancy and % change in clinical symptoms as indexed by either the BPRS or the PANSS, our final analysis consisted of 16 imaging studies (20 cohorts; N=206).

RESULTS

The first step of the meta-analysis confirmed the positive relationship between antipsychotic medication and clinical improvement in SCZ (ES=1.36; 95% CI: 1.13-1.60). The second step of our analysis revealed that when D₂ occupancy was limited to less than 80% in order to control for the appearance of extrapyramidal symptoms, high D₂ occupancy was correlated with reduction in clinical scores (r=0.4, p<0.001) for medications other than clozapine or quetiapine.

CONCLUSIONS

Our results suggest that D₂ occupancy is a contributing factor for the mechanism of antipsychotic effect in SCZ for some but not all antipsychotic medications.

In vivo quantification of striatal dopamine D2 receptor occupancy by JNJ-37822681 using [11C]raclopride and positron emission tomography

JNJ-37822681 is a novel, fast-dissociating dopamine D(2) receptor antagonist, currently in development as an antipsychotic drug candidate. A previous first-in-human study demonstrated mild central nervous system effects of JNJ-37822681 in healthy male volunteers. Significant but transient serum prolactin elevations were demonstrated, whereas other neurophysiological effects were relatively small. To investigate striatal dopamine D(2) receptor occupancy by variable single doses of JNJ-37822681, an open-label [(11)C]raclopride positron emission tomography study was performed in 12 healthy male volunteers, using the simplified reference tissue model with cerebellum as reference tissue. Oral administration of JNJ-37822681 resulted in dose-dependent dopamine D(2) receptor occupancy. Receptor occupancy increased from 9-19% at 2 mg doses to 60-74% at 20 mg doses of JNJ-37822681. Therefore, single oral doses of JNJ-37822681 can produce occupancy levels that are generally associated with clinical efficacy for registered antipsychotic drugs.

Dopamine D2 receptor occupancy with risperidone or olanzapine during maintenance treatment of schizophrenia: a cross-sectional study

In treating schizophrenia, it has been established that 65-80% occupancy of dopamine D2 receptors optimizes therapeutic efficacy while minimizing risks of extrapyramidal symptoms. However, it is unclear as to whether it is necessary to keep D2 receptor occupancy within this therapeutic window to maintain response. In this study, daily peak and trough D2 receptor occupancy levels were estimated in clinically stable patients with schizophrenia (DSM-IV) who were receiving risperidone or olanzapine. Using two collected plasma samples, plasma antipsychotic concentrations at peak and trough were estimated with population pharmacokinetic techniques. Corresponding dopamine D2 receptor occupancy levels were then estimated, using a recently developed model. 35 subjects with stable schizophrenia completed the study (mean±SD age, 48.8±13.8years; male [N=14]; Asians [N=23], Caucasians [N=12]; risperidone [N=20] at 3.2±2.3mg/day, and olanzapine [N=15] at 9.2±4.9mg/day) between September and December 2010. 48.6% (N=17) did not achieve a continuous blockade of ≥65%. Moreover, 11.4% (N=4) did not achieve the 65% threshold at estimated peak concentrations. In conclusion, approximately half the subjects with stable schizophrenia did not achieve estimated continuous blockade of D2 receptor occupancy of ≥65%. The results suggest that sustained D2 receptor occupancy levels of ≥65% may not always be necessary for the maintenance treatment of schizophrenia.

Antipsychotic treatment for schizophrenia in the maintenance phase: a systematic review of the guidelines and algorithms

OBJECTIVE

Antipsychotic treatment strategy for the maintenance phase of schizophrenia has been inconsistent in the literature. The purpose of this systematic review is to overview recommendations in various guidelines and algorithms.

METHODS

The guidelines and algorithms for schizophrenia that were published or updated in English after 2000 were searched, using Medline, PubMed, EMBASE, and PsycINFO with the following key words: guideline, algorithm, schizophrenia, and psychosis (last search: July 2011). The reference lists of the relevant reports were also examined.

RESULTS

Fourteen guidelines and algorithms were identified; only five of them clearly defined terms about the maintenance phase and treatment. Ten of 11 guidelines and algorithms did not recommend discontinuation of antipsychotics within five years; six of them partially recommended antipsychotic discontinuation for patients with first-episode schizophrenia exclusive. All nine guidelines and algorithms that referred to intermittent or targeted antipsychotic strategy endorsed against this strategy. Although being a hot topic of controversy, dose reduction of antipsychotics or lower dose therapy in the maintenance phase compared to the acute dosage is not recommended on the whole concerning atypical antipsychotics, whereas dose reduction appears sometimes considered acceptable for typical antipsychotics.

CONCLUSION

What constitutes maintenance phase and its treatment in schizophrenia has not yet been established in the literature. While discontinuation and intermittent or targeted strategies are not generally recommended, there is controversy regarding dose reduction or lower dose therapy, especially with regards to atypical antipsychotics. Further evidence is needed in order to derive treatment recommendations on antipsychotics in this critical treatment phase of schizophrenia.

Schizophrenia as a disorder of too little dopamine: implications for symptoms and treatment

Antipsychotics represent the first effective therapy for schizophrenia, with their benefits linked to dopamine D2 blockade. Schizophrenia was soon identified as a hyperdopaminergic disorder, and antipsychotics proved to be reasonably effective in controlling positive symptoms. However, over the years, schizophrenia has been reconceptualized more broadly, now defined as a heterogeneous disorder with multiple symptom domains. Negative and cognitive features, not particularly responsive to antipsychotic therapy, have taken on increased importance--current thinking suggests that these domains predate the onset of positive symptoms and are more closely tied to functional outcome. That they are better understood in the context of decreased dopamine activity suggests that schizophrenia may fundamentally represent a hypodopaminergic disorder. This shift in thinking has important theoretical implications from the standpoint of etiology and pathophysiology, but also clinically in terms of treatment and drug development.

Modeling chronic olanzapine exposure using osmotic minipumps: pharmacological limitations

Animal models can face unique challenges in mirroring what occurs in humans. This is the case for antipsychotics in rodents, where these drugs are metabolized much more rapidly. One strategy to address this issue has been the use of osmotic minipumps to ensure continuous antipsychotic exposure over prolonged intervals, which is routinely the case when these same drugs are administered to humans. More recently, it has been identified that with olanzapine this approach may be compromised by oxidative degradation, a process that can be observed within days. Further, in vivo evidence has reported progressive decreases in plasma levels over a 1-month interval. To address this issue in vitro, osmotic minipumps (n=4), with olanzapine at a concentration resulting in a dose of 7.5mg/kg/day in vivo, were placed in saline-filled Falcon tubes and immersed in a water bath. Olanzapine concentrations were assessed in the minipumps as well as the surrounding water bath at baseline, 1h, and days 1, 7, 14, 21, and 28. Minipump results indicated a monophasic exponential decay and a half-life of 14.8 days (95% CI=13.1-17.1 days). Results from the water bath demonstrated a linear increase in olanzapine up to and including day 21, followed thereafter by a decrease to day 28. It is concluded that administration of olanzapine via osmotic minipump is viable in animal models to mirror what occurs in humans, although the interval should be confined to 2 weeks. As well, strategies in dissolving olanzapine to diminish oxidation are discussed.

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.

Emotion processing in schizophrenia: fMRI study of patients treated with risperidone long-acting injections or conventional depot medication

We employed two event-related functional magnetic resonance imaging tasks using the pictures of mild and intense facial emotions of fear or happiness. The sample comprised 16 chronic schizophrenia patients treated with risperidone long-acting injections (RLAI), 16 patients treated with conventional antipsychotic depots (CONV) and 16 healthy controls (HC). The HC and RLAI groups demonstrated greater activation in the left amygdala in response to intensively fearful faces, and in right cerebellum to intensively happy faces compared with CONV patients. The CONV group demonstrated under-activation in the right temporal pole in response to intensively happy faces (compared with HC) and over-activation in ventro-medial prefrontal cortex (VMPFC) in response to both intensively happy and fearful expressions, compared with HC and RLAI groups. Our results suggest that networks implicated in the allocation of attentional resources (VMPFC) and emotion processing (amygdala, cerebellum) are differentially affected in patients on CONV versus RLAI.

Antipsychotic occupancy of dopamine receptors in schizophrenia

Antipsychotic drugs were introduced in the early 50s on the basis of clinical observations in patients with schizophrenia. Experimental studies later revealed that antagonism at the D(2) dopamine receptor is a common characteristic of all antipsychotic drugs. In the 80s, the advent of brain imaging technologies such as positron emission tomography (PET) allowed for direct noninvasive studies of drug binding in treated patients. The concept receptor occupancy is defined as the fraction (%) of a receptor population that is occupied during treatment with an unlabelled drug. With regard to antipsychotic drugs, the radioligand [(11) C]-raclopride has been the most widely used for binding to the D(2) /D(3) -dopamine receptors. The present review discusses the contribution from molecular imaging to the current understanding of mechanism of action (MoA) of antipsychotic drugs. Consistent initial PET-findings of high D2-receptor occupancy in the striatum of patients responding to different antipsychotic drug treatments provided clinical support for the dopamine hypothesis of antipsychotic drug action. It has subsequently been demonstrated that patients with extrapyramidal syndromes (EPS) have higher occupancy (above 80%) than patients with good response but no EPS (65-80%). The PET-defined interval for optimal antipsychotic drug treatment has been implemented in the evolvement of dose recommendations for classical as well as more recently developed drugs. Another consistent finding is lower D(2) -occupancy during treatment with the prototype atypical antipsychotic clozapine. The MoA of clozapine remains to be fully understood and may include nondopaminergic mechanisms. A general limitation is that currently available PET-radioligands are not selective for any of the five dopamine receptor subtypes. Current attempts at developing such ligands may provide the tools required to refine further the MoA of antipsychotic drugs.

Drug delivery to the brain: considerations of genetic polymorphisms of blood-brain barrier transporters and imaging technologies

PubMed search and literature reviews summarized our latest advances regarding the impact of genetic polymorphisms of blood-brain barrier transporters on, and the application of imaging technologies to evaluate and enhance drug delivery to the brain. Although there are reports relating transporter polymorphisms to pharmacokinetics or adverse events, few studies have extended such efforts to the brain. Conceivably, simultaneous nonfunctional expressions of more than one key efflux transporters could result in devastating clinical outcomes if the dose of their substrate drug is not adjusted for the subpopulation with such a phenotype. Imaging technologies have been used to elucidate the kinetic or functional activities of blood-brain barrier transporters, with the majority focusing on P-glycoprotein. Imaging technologies have been used to discover drugs for treating brain disorders, enable targeted delivery in combination with convection-enhanced delivery, assess the therapeutic effect of a treatment protocol and assess drug penetration into brain tumors. Research is limited, however, in using imaging technologies to link the genotype or phenotype of a transporter to the uptake of drug into the brain. No imaging studies have provided clear evidence of transporter polymorphisms discriminating the distribution of drug in the brain. Research efforts are needed to use imaging technologies to explore the correlation between pharmacogenetics and individual clinical outcomes, especially for the phenotype of more than one nonfunctional transporters.

Antipsychotic dosing: how much but also how often?

Considerable focus has been devoted to how much antipsychotic is appropriate for optimal clinical response, although how often antipsychotics need to be administered is also less than clear. Clinicians are aware of the increased risk of relapse related to antipsychotic nonadherence/discontinuation, and current practice dictates continuous antipsychotic exposure with the goal of achieving steady state-levels to maintain effectiveness and prevent relapse. Does this mean we need to (or should) administer antipsychotics at least daily? There is a body of evidence challenging this long-established clinical axiom.

Second-generation antipsychotic long-acting injections: systematic review

BACKGROUND

Second-generation antipsychotics (SGAs) represent an advance in the long-term management of schizophrenia.

AIMS

To review the available evidence concerning SGA long-acting injections (LAIs).

METHOD

A systematic review of the literature was conducted using PubMed.

RESULTS

Risperidone long-acting injection was the first licensed SGA-LAI compound and is effective in the long-term management of schizophrenia, with a safety profile similar to that of oral risperidone. Olanzapine pamoate has recently been approved in Europe. In terms of efficacy, at injection intervals of up to 4 weeks it appears comparable to oral olanzapine, although the potential for ;post-injection syndrome' (delirium) calls for additional safety considerations. Paliperidone palmitate is currently under review with the licensing authorities. It also affords the potential advantage of monthly dosing.

CONCLUSIONS

More long-term comparisons of SGA-LAIs with oral SGAs as well as with first-generation antipsychotic LAIs are needed. These studies should include cost-effectiveness data.

Long-acting injectable antipsychotics: focus on olanzapine pamoate

Medication non-adherence in patients with schizophrenia continues to be a significant problem and threatens successful treatment outcomes. Medication non-adherence is often associated with negative consequences, including symptom exacerbation, more frequent emergency room visits, re-hospitalizations and relapse. Long-acting injectable (LAI) forms of antipsychotics allow for rapid identification of non-adherence, obviate the need for the patient to take the medication on a daily basis and increase adherence to some significant degree. Eli Lilly has developed a long-acting depot formulation of olanzapine, olanzapine pamoate, which has recently been approved by the FDA for the US market, and which will be reviewed here. Olanzapine LAI appears to be an effective antipsychotic at dosages of 210 mg every 2 weeks, 300 mg every 2 weeks and 405 mg every 4 weeks in patients with acute schizophrenia, and at 150 mg every 2 weeks, 300 mg every 2 weeks and at 405 mg every 4 weeks for the maintenance treatment of stable patients. Oral supplementation appears not to be needed, particularly not at the onset of treatment with the LAI as is necessary with risperidone LAI. Its efficacy is in general comparable to the efficacy seen with oral olanzapine at a corresponding dose. The side effect profile is also comparable to the side effects observed with oral olanzapine, including lower rates of extrapyramidal symptoms, prolactin elevation and cardiovascular side effects, but significant metabolic effects. The latter include significant weight gain, lipid abnormalities and glucose dysregulation. While the injection site adverse events are overall mild, the most significant serious adverse event is the post-injection delirium sedation syndrome (PDSS). While rare, this syndrome results from inadvertent intravascular injection of olanzapine LAI and can cause a range of olanzapine overdose-type of symptoms. Olanzapine LAI needs therefore to be administered by trained personnel in settings where a post-injection observation period for at least 3 hours by medical personnel is available. The overall use of olanzapine LAI will probably be limited by the possibility of a PDSS event. Patients who have a history of good response to oral olanzapine and are in need of assured medication administration may present a good indication for its use, provided that the appropriate mental health delivery setting is available.

Mechanisms underlying psychosis and antipsychotic treatment response in schizophrenia: insights from PET and SPECT imaging

Molecular imaging studies have generated important in vivo insights into the etiology of schizophrenia and treatment response. This article first reviews the PET and SPECT evidence implicating dopaminergic dysfunction, especially presynaptic dysregulation, as a mechanism for psychosis. Second, it summarises the neurochemical imaging studies of antipsychotic action, focussing on D2/3 receptors. These studies show that all currently licensed antipsychotic drugs block striatal D2/3 receptors in vivo- a site downstream of the likely principal dopaminergic pathophysiology in schizophrenia- and that D2/3 occupancy above a threshold is required for antipsychotic treatment response. However, adverse events, such as extra-pyramidal side-effects or hyperprolactinemia, become much more likely at higher occupancy levels, which indicates there is an optimal 'therapeutic window' for D2/3 occupancy, and questions the use of high doses of antipsychotic treatment in clinical practice and trials. Adequate D2/3 blockade by antipsychotic drugs is necessary but not always sufficient for antipsychotic response. Molecular imaging studies of clozapine, the one antipsychotic licensed for treatment resistant schizophrenia, have provided insights into the mechanisms underlying its unique efficacy. To link this pharmacology to the phenomenology of the illness, we discuss the role of dopamine in motivational salience and show how i) psychosis could be viewed as a process of aberrant salience, and ii) antipsychotics might provide symptomatic relief by blocking this aberrant salience. Finally, we discuss the implications of these PET and SPECT findings for new avenues of drug development.

Dosing of antipsychotics in schizophrenia across the life-spectrum

Age effects on dosing of antipsychotics in schizophrenia and mechanisms underlying those effects have not been well understood. The objective of this article is to review the literature regarding effects of age on antipsychotic dosing in schizophrenia and potential mechanisms underlying the age-related antipsychotic sensitivity. According to prescription surveys, age appears to have biphasic effects on prescribed antipsychotic dose. The dose increased with age through the third decade, subsequently plateaued, and decreased after the fifth decade. The first half of this inverted U-shaped relationship may be attributable to a deterioration process in the early phase of schizophrenia and the contribution of 'tachyphylaxis' of antipsychotics on the dopaminergic system. The following age-related decline in prescribed dose is likely associated with physiological aging. Recent data suggest that this increased antipsychotic sensitivity with age comes from age-related functional decline in the dopaminergic system, including endogenous dopamine level and dopamine receptor density. Although the evidence on potential mechanisms underlying age effects on antipsychotic dosing is still limited, alterations in the dopaminergic system due to aging and chronic exposure to this drug may contribute to the inverted U-shaped relationship between dose and age. This age-related antipsychotic sensitivity highlights the importance of finding the lowest possible effective dose of antipsychotic drugs as patients age to enhance therapeutic effects as well as minimize their side effects.

The 'atypicality' of antipsychotics: a concept re-examined and re-defined

Recent clinical trials have raised questions over the perceived advantages of second-generation 'atypical' antipsychotics over those from the first generation. An atypical antipsychotic in its original sense is one that lacks extrapyramidal side effects. However, the addition of other clinical features to the original concept of atypicality, such as efficacy against negative and cognitive symptoms, seems to have become a feature of searches for novel antipsychotics in the past two decades. Although this approach has led to some therapeutic advances, we propose that it has also hampered antipsychotic drug research and that reframing the concept of atypicality could have a key role in making genuine breakthroughs in schizophrenia therapy.