Tardive dyskinesia in relation to estimated dopamine D2 receptor occupancy in patients with schizophrenia: analysis of the CATIE data

Shared GABA transmission pathology in dopamine agonist- and antagonist-induced dyskinesia

Dyskinesia is involuntary movement caused by long-term medication with dopamine-related agents: the dopamine agonist 3,4-dihydroxy-L-phenylalanine (L-DOPA) to treat Parkinson's disease (L-DOPA-induced dyskinesia [LID]) or dopamine antagonists to treat schizophrenia (tardive dyskinesia [TD]). However, it remains unknown why distinct types of medications for distinct neuropsychiatric disorders induce similar involuntary movements. Here, we search for a shared structural footprint using magnetic resonance imaging-based macroscopic screening and super-resolution microscopy-based microscopic identification. We identify the enlarged axon terminals of striatal medium spiny neurons in LID and TD model mice. Striatal overexpression of the vesicular gamma-aminobutyric acid transporter (VGAT) is necessary and sufficient for modeling these structural changes; VGAT levels gate the functional and behavioral alterations in dyskinesia models. Our findings indicate that lowered type 2 dopamine receptor signaling with repetitive dopamine fluctuations is a common cause of VGAT overexpression and late-onset dyskinesia formation and that reducing dopamine fluctuation rescues dyskinesia pathology via VGAT downregulation.

Treatment of severe tardive dyskinesia with concurrent administration of olanzapine, clonazepam, baclofen, and gabapentin: a case report

BACKGROUND

Long-term use of antipsychotics or other dopamine antagonists can result in the extrapyramidal side effect of tardive dyskinesia (TD).Case presentation: An 18-year-old female patient experienced abnormal speech and behavior and because of an equivocal diagnosis, she was given daily doses of 300 mg of quetiapine and 60 mg of ziprasidone. She had used these medications for 2 years before the appearance of involuntary abnormal movements. These movements, which were classified as TD, steadily worsened and markedly interfered with her daily life. Following a trial-and-error course of therapy with vitamin E, vitamin B6, amantadine, valproic acid sodium, lorazepam, and diazepam, the drugs were gradually reduced and stopped, yet the aberrant movements persisted. Finally, the patient was given olanzapine, clonazepam, baclofen, and gabapentin. The Abnormal Involuntary Movement Scale was used to assess changes in the patient's condition. Her TD was efficiently managed through co-administration of olanzapine, clonazepam, baclofen, and gabapentin.

CONCLUSIONS

The possibility of TD inducing by antipsychotic use is a clinical concern, even though atypical antipsychotics decrease the incidence of extrapyramidal side effects, and it cannot be entirely excluded. This report provides useful insights into the management of TD and will help clinicians manage similar cases.

Improvement of Tardive Dyskinesia during Mindfulness Meditation

Background: We report the case of a patient presenting with orofacial tardive dyskinesia (TD), following administration of a first-generation antipsychotic (Loxapine). Intervention: Four weeks of repeated sessions of mindfulness-based cognitive therapy (MBCT) and mindfulness-based stress reduction (MBSR) protocols were administered, with TD hetero-quantified before and during each session via the Abnormal Involuntary Movement Scale (AIMS). Results: The dyskinesia ameliorated quantitatively and qualitatively (1) during each session, and (2) at resting conditions in the long term. During some sessions, after which patients’ compliance was auto-evaluated as maximal, complete arrest of the TD was observed. Hypothesis and Conclusion: We suggest mindfulness meditation as a novel adjunctive therapeutic approach for tardive dyskinesia, and invite for further clinical and neurological investigations.

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.

Antipsychotic treatment and basal ganglia volumes: Exploring the role of receptor occupancy, dosage and remission status

Antipsychotic treatment may affect brain morphology, and enlargement of the basal ganglia (BG) is a replicated finding. Here we investigated associations between antipsychotic treatment and BG volumes in patients with psychotic and bipolar disorders. We hypothesized that current treatment and, among those medicated, higher dosage, estimated D2R occupancy and being in remission would predict larger BG volumes. Structural covariance analysis was performed to examine if correlations between BG volumes and cortical thickness differed by treatment status. 224 patients treated with antipsychotics; 26 previously treated, 29 never treated and 301 healthy controls (HC) were included from the TOP study cohort (NORMENT, Norway). T1-weighted MR images were processed using FreeSurfer. D2R occupancy was estimated based on serum concentration measurements for patients receiving stable monotherapy. Statistical analyses were adjusted for age, gender and estimated intracranial volume (ICV). We found larger right (p < 0.003) and left putamen (p < 0.02) and right globus pallidus (GP) (p < 0.03) in currently medicated patients compared to HC. Bilateral regional cortical thinning was also observed in currently and previously medicated patients compared to HC. In medicated patients, higher chlorpromazine equivalent dose (CPZ) was associated with larger left GP (p < 0.04). There was no association with estimated D2R occupancy (n = 47) or remission status. Lower positive correlation between left putamen volume and cortical thickness of the left lateral occipital cortex was found in medicated patients compared to HC. We replicated the BG enlargement in medicated patients, but found no association with estimated D2R occupancy. Further studies are needed to clarify the underlying mechanisms.

The effects of illness severity, cognition, and estimated antipsychotic dopamine receptor occupancy on insight into the illness in schizophrenia: An analysis of clinical antipsychotic trials of intervention effectiveness (CATIE) data

BACKGROUND

The relationship between dopamine D₂ receptor (D₂R) occupancy and impaired illness awareness (IIA) remains unclear. While IIA is associated with illness severity and cognitive dysfunction, antipsychotic medication, the principal treatment for schizophrenia, indirectly improves IIA, but may simultaneously contribute to cognitive dysfunction at supratherapeutic doses.

AIM AND METHODS

We investigated the influence of estimated D₂R (Est.D₂R) occupancy by antipsychotics on the relationships between IIA and illness severity, and IIA and cognition. IIA was assessed in 373 adult patients with schizophrenia (18-62 years) using data from CATIE. IIA was measured using the Positive and Negative Syndrome Scale (PANSS) item G12. D₂R occupancy levels were estimated from plasma concentrations for risperidone, olanzapine, and ziprasidone. Correlation, regression, and path analyses were performed to examine IIA's relationship to illness severity, cognition, and Est.D₂R.

RESULTS

Illness severity was predictive of IIA. However, premorbid IQ, cognition, and Est.D₂R did not predict IIA, and Est.D₂R did not serve either a moderating or mediating role in both regression and path analyses.

CONCLUSIONS

Consistent with previous literature, our results suggest that IIA is a function of illness severity in adult patients with schizophrenia. Future studies should explore whether D₂R occupancy mediates the relationships between IIA and illness severity, and IIA and cognitive dysfunction, in late-life schizophrenia (i.e. ≥60 years) given the effects of aging on cognition, IIA, and antipsychotic sensitivity.

Classics in Chemical Neuroscience: Risperidone

After the identification of the influence of serotonergic receptors in ameliorating the negative symptoms associated with schizophrenia, atypical antipsychotics were developed by incorporating dopamine and serotonin antagonism. Risperidone, sold under the trade name Risperdal, was the second atypical antipsychotic developed following clozapine but quickly became a first-line treatment for acute and chronic schizophrenia because of its preferential side effect profile. Despite initial Food and Drug Administration approval 25 years ago, risperidone continues to be a fundamental treatment for schizophrenia, bipolar I disorder, and autism-related irritability. It is on the World Health Organization's List of Essential Medicines for its balance of efficacy, safety, tolerability, and cost-effectiveness. In this review, we highlight the history and importance of risperidone as an atypical antipsychotic, in addition to its chemical synthesis, manufacturing, drug metabolism and pharmacokinetics, pharmacology, structure-activity relationship, indications, and adverse effects.

Genetics of tardive dyskinesia: Promising leads and ways forward

Tardive dyskinesia (TD) is a potentially irreversible and often debilitating movement disorder secondary to chronic use of dopamine receptor blocking medications. Genetic factors have been implicated in the etiology of TD. We therefore have reviewed the most promising genes associated with TD, including DRD2, DRD3, VMAT2, HSPG2, HTR2A, HTR2C, and SOD2. In addition, we present evidence supporting a role for these genes from preclinical models of TD. The current understanding of the etiogenesis of TD is discussed in the light of the recent approvals of valbenazine and deutetrabenazine, VMAT2 inhibitors, for treating TD.

Risperidone versus olanzapine among patients with schizophrenia participating in supported employment: Eighteen-month outcomes

This study compares the efficacy and tolerability of olanzapine versus risperidone among patients with schizophrenia who are established in outpatient psychiatric care and entering supported employment. A multicenter, randomized, double-blind trial was conducted among 107 outpatients with schizophrenia, who were cross-titrated to flexible dose risperidone or olanzapine over 2 weeks. Clinical endpoints included time to hospitalization and persistence on assigned medication. Weight, laboratory tests, psychopathology, neurologic side effects, social adjustment and role functioning were assessed at 3-6 month intervals. Data were analyzed first by randomized treatment, and then reassessed controlling for prior medication treatment. The proportion of patients on assigned medication at 18 months was 30.9% for risperidone and 37.3% for olanzapine. Mean doses were 6.4 ± 3.2 mg daily for risperidone, and 17.0 ± 5.0 mg daily for olanzapine. The groups did not differ significantly in time to medication discontinuation, first hospitalization or first employment. There were few differences in psychopathology, laboratory, or neurological assessments between groups at 18 months. Patients randomized to olanzapine gained modestly more weight. Controlling for pre-randomization medication suggested improvement in some aspects of psychopathology from switching medications; however, switching from olanzapine to risperidone was associated with more hospitalizations. Risperidone and olanzapine have similar efficacy and tolerability in patients with schizophrenia who are participating in supported employment. Randomization to olanzapine was associated with more weight gain, but randomization from olanzapine to risperidone appeared to be associated with a greater likelihood of hospitalization. Careful monitoring of metabolic effects and participation in supported employment may have contributed to minimal weight gain and metabolic effects.

Classics in Chemical Neuroscience: Aripiprazole

Aripiprazole was the first antipsychotic developed to possess agonist properties at dopamine D₂ autoreceptors, a groundbreaking strategy that presented a new vista for schizophrenia drug discovery. The dopamine D₂ receptor is the crucial target of all extant antipsychotics, and all developed prior to aripiprazole were D₂ receptor antagonists. Extensive blockade of these receptors, however, typically produces extrapyramidal (movement) side effects, which plagued first-generation antipsychotics, such as haloperidol. Second-generation antipsychotics, such as clozapine, with unique polypharmacology and D₂ receptor binding kinetics, have significantly lower risk of movement side effects but can cause myriad additional ones, such as severe weight gain and metabolic dysfunction. Aripiprazole's polypharmacology, characterized by its unique agonist activity at dopamine D₂ and D₃ and serotonin 5-HT_1A receptors, as well as antagonist activity at serotonin 5-HT_2A receptors, translates to successful reduction of positive, negative, and cognitive symptoms of schizophrenia, while also mitigating risk of weight gain and movement side effects. New observations, however, link aripiprazole to compulsive behaviors in a small group of patients, an unusual side effect for antipsychotics. In this review, we discuss the chemical synthesis, pharmacology, pharmacogenomics, drug metabolism, and adverse events of aripiprazole, and we present a current understanding of aripiprazole's neurotherapeutic mechanisms, as well as the history and importance of aripiprazole to neuroscience.

Behavioral and qEEG effects of the PDE10A inhibitor THPP-1 in a novel rhesus model of antipsychotic activity

RATIONALE

Much preclinical data, almost exclusively using rodent, supports the notion that phosphodiesterase 10A (PDE10A) inhibition may offer an alternative to the current standard of care in schizophrenia. However, concerns persist regarding the clinical translatability of these models for newer drug classes like PDE10A inhibitors.

OBJECTIVES

We therefore sought to characterize the clinical standard risperidone and the PDE10A inhibitor THPP-1 in nonhuman primate, both alone and when used as a combination therapy.

METHODS

THPP-1 and risperidone were tested in a novel rhesus model of stimulant-induced motor activity (SIMA) and in rhesus electroencephalography (EEG).

RESULTS

Consistent with rodent data, both THPP-1 and risperidone significantly attenuated the stimulant effects in SIMA when administered alone, though some differences were noted. Combination therapy with a low dose of risperidone produced significantly more robust effects. THPP-1 and risperidone also produced a marked reduction of wake cycle time and gamma frequency power in EEG. However, THPP-1 differed from risperidone by reducing spectral power of lower frequencies (delta).

CONCLUSIONS

SIMA results suggest that PDE10A inhibition produces antipsychotic-like effects in higher species, and that combination therapy with PDE10A inhibitors may produce more robust efficacy compared to monotherapies. EEG and qEEG results confirm that PDE10A inhibition does share some central signaling effects with clinically effective antipsychotics. The present combination therapy results may carry implications for the manner in which clinical testing of PDE10A inhibitors is conducted.

Adjunctive use of interferon γ inducer for treatment of patients with schizophrenia

OBJECTIVE

The present paper is devoted to evaluation of clinical and immunomodulatory effect of ultra-high dilutions of antibodies to human interferon γ, included in the complex therapy of patients with schizophrenia. Materials and methods The study was carried out at the Mental Health Research Institute, Tomsk, Russian Federation. This double-blind, placebo-controlled randomised in parallel-group study enrolled 40 patients. As a part of complex therapy, patients from the main group (n=20) received anaferon, a drug containing ultra-high dilutions of affinity-purified antibodies to human interferon γ as the active pharmaceutical ingredient; patients from the comparative group (n=20) received placebo. Duration of the therapy was 30±5 days. Assessment of severity of symptoms and changes in them were made using clinical scales: Positive and Negative Syndrome Scale, Clinical Global Impression, Abnormal Involuntary Movements Scale. Spontaneous and phytohemagglutinin-induced production of interferon γ by immunocompetent cells in supernatants of 48 h whole blood culture of patients was measured by enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The reduction of interferon-producing potential by immunocompetent cells in comparison with reference normal value was shown in total group of patients (n=40) before combined therapy. During the treatment, increase of spontaneous interferon γ production and favourable changes in psychopathological symptoms as compared with placebo were shown in subjects receiving anaferon. It was found that favourable changes in clinical symptoms assessed using clinical scales with a high degree of confidence correlated with high level of spontaneous interferon γ production.

CONCLUSION

Anaferon as a part of complex therapy of patients with schizophrenia contributes to enhancement of its efficacy acting via mechanism of psychoimmunomodulation.

Dopamine D2/3 Receptor Occupancy Following Dose Reduction Is Predictable With Minimal Plasma Antipsychotic Concentrations: An Open-Label Clinical Trial

BACKGROUND

Population pharmacokinetics can predict antipsychotic blood concentrations at a given time point prior to a dosage change. Those predicted blood concentrations could be used to estimate the corresponding dopamine D2/3 receptors (D2/3R) occupancy by antipsychotics based on the tight relationship between blood and brain pharmacokinetics. However, this 2-step prediction has never been tested.

METHODS

Two blood samples were collected at separate time points from 32 clinically stable outpatients with schizophrenia (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; mean ± SD age: 60.1 ± 7.3 years) to measure plasma concentrations of olanzapine or risperidone at baseline. Then, subjects underwent a dose reduction of olanzapine or risperidone and completed a [(11)C]-raclopride positron emission tomography scan to measure D2/3R occupancy in the putamen. The plasma concentration at the time of the scan was predicted with the 2 samples based on population pharmacokinetic model, using NONMEM. D2/3R occupancy was then estimated by incorporating the predicted plasma concentration in a hyperbole saturation model. The predicted occupancy was compared to the observed value.

RESULTS

The mean (95% CI) prediction errors for the prediction of D2/3R occupancy were -1.76% (-5.11 to 1.58) for olanzapine and 0.64% (-6.18 to 7.46) for risperidone. The observed and predicted D2/3R occupancy levels were highly correlated (r = 0.67, P = .001 for olanzapine; r = 0.67, P = .02 for risperidone).

CONCLUSIONS

D2/3R occupancy levels can be predicted from blood drug concentrations collected prior to dosage change. Although this 2-step model is subject to a small degree of error, it could be used to select oral doses aimed at achieving optimal D2/3R occupancy on an individual basis.

Motor dysfunction within the schizophrenia-spectrum: A dimensional step towards an underappreciated domain

At the beginning of the 20th century, genuine motor abnormalities (GMA) were considered to be intricately linked to schizophrenia. Subsequently, however, GMA have been increasingly regarded as unspecific transdiagnostic phenomena or related to side effects of antipsychotic treatment. Despite possible medication confounds, within the schizophrenia spectrum GMA have been categorized into three broad categories, i.e. neurological soft signs, abnormal involuntary movements and catatonia. Schizophrenia patients show a substantial overlap across a broad range of distinct motor signs and symptoms suggesting a prominent involvement of the motor system in disease pathophysiology. There have been several attempts to increase reliability and validity in diagnosing schizophrenia based on behavior and neurobiology, yet relatively little attention has been paid to the motor domain in the past. Nevertheless, accumulating neuroscientific evidence suggests the possibility of a motor endophenotype in schizophrenia, and that GMA could represent a specific dimension within the schizophrenia-spectrum. Here, we review current neuroimaging research on GMA in schizophrenia with an emphasis on distinct and common mechanisms of brain dysfunction. Based on a dimensional approach we show that multimodal neuroimaging combined with fine-grained clinical examination can result in a comprehensive characterization of structural and functional brain changes that are presumed to underlie core GMA in schizophrenia. We discuss the possibility of a distinct motor domain, together with its implications for future research. Investigating GMA by means of multimodal neuroimaging can essentially contribute at identifying novel and biologically reliable phenotypes in psychiatry.

Tardive dyskinesia occurring in a young woman after withdrawal of an atypical antipsychotic drug

Tardive dyskinesia (TD) is one of the most serious and disturbing side-effects of dopamine receptor antagonists. It affects 20-50% of patients on long-term antipsychotic therapy. The pathophysiology of TD remains poorly understood, and treatment is often challenging. Here, we present a 32-year-old woman presenting with a 9-month history of TD occurring after risperidone withdrawal, and characterized almost exclusively by tongue protrusion. After being seen by different specialties and undergoing multiple investigations, she was eventually correctly diagnosed with TD by a specialist team and successfully treated with amantadine. Vigilance and awareness of this condition and its risk factors are required to make the correct diagnosis, especially in cases with unusual presentations caused by atypical antipsychotics, and treatment can be challenging.