Recent Advances in the Pharmacology of Tardive Dyskinesia

Treatment of tardive dyskinesia with clonazepam: A case report

Clonazepam has some evidence in the treatment of tardive dyskinesia. It can be used as an alternative treatment option in situations where vesicular monoamine transporter 2 inhibitors are not available or when it is not feasible to use them.

Analysis of schizophrenia-associated genetic markers in the HLA region as risk factors for tardive dyskinesia

OBJECTIVES

The pathology of Tardive Dyskinesia (TD) has yet to be fully understood, but there have been proposed hypotheses for the cause of this condition. Our team previously reported a possible association of TD with the Complement Component C4 gene in the HLA region. In this study, we explored the HLA region further by examining two previously identified schizophrenia-associated HLA-region single-nucleotide polymorphisms (SNPs), namely rs13194504 and rs210133.

METHODS

The SNPs rs13194504 and rs210133 were tested for association with the occurrence and severity of TD in a sample of 172 schizophrenia patients who were recruited for four studies from three different clinical sites in Canada and USA.

RESULTS

The rs13194504 AA genotype was associated with decreased severity for TD as measured by Abnormal Involuntary Movement Scale (AIMS) scores (p = 0.047) but not for TD occurrence. SNP rs210133 was not significantly associated with either TD occurrence or AIMS scores.

CONCLUSION

Our findings suggest that the rs13194504 AA genotype may play a role in TD severity, while SNP rs210133 may not have a major role in the risk or severity of TD.

Tardive dyskinesia in Asia- current clinical practice and the role of neurologists in the care pathway

Tardive dyskinesia (TD) is a movement disorder that can arise as a side effect of treatment with dopamine receptor-blocking agents (DRBAs), including antipsychotic drugs (APDs) used to manage psychotic illnesses. Second-generation APDs (SGAs) are often preferred to first-generation drugs due to their lower propensity to cause TD, however many SGAs-treated patients still develop the condition. Although TD is a global health concern, evidence regarding the occurrence of TD and how it is managed in Asian countries is currently limited. This article reports the results of a systematic review of the published literature on TD focusing on its prevalence, types of patients, knowledge of the condition, causative factors, and usual treatment pathways in clinical practice in Asian countries. Epidemiological data suggest that the prevalence of TD is increasing globally due to an overall rise in APD use, contributing factors being polypharmacy with multiple APDs, the use of higher than necessary doses, and off-label use for non-psychotic indications. Although exact prevalence figures for TD in Asian countries are difficult to define, there is a similar pattern of rising APD use which will result in increasing numbers of TD patients in this region. These issues need to be addressed and strategies developed to minimize TD risk and manage this disabling condition which impacts patients' quality of life and daily functioning. To date, both research into TD has been predominantly psychiatry focused and the perspectives from neurologists regarding the clinical management of this challenging condition are scarce. However, neurologists have an essential role in managing the movement disorders manifestations that characterize TD. Optimum management of TD, therefore, should ideally involve collaboration between psychiatrists and neurologists in joint care pathways, wherever practical. Collaborative pathways are proposed in this article, and the challenges that will need to be addressed in Asian countries to improve the care of people with TD are highlighted, with a focus on the neurologist's viewpoint and the implications for the management of TD globally.

Parakinesia: A Delphi consensus report

Abnormal movements are intrinsic to some forms of endogenous psychoses. Spontaneous dyskinesias are observed in drug-naïve first-episode patients and at-risk subjects. However, recent descriptions of spontaneous dyskinesias may actually represent the rediscovery of a more complex phenomenon, 'parakinesia' which was described and documented in extensive cinematographic recordings and long-term observations by German and French neuropsychiatrists decades before the introduction of antipsychotics. With the emergence of drug induced movement disorders, the description of parakinesia has been refined to emphasize the features enabling differential diagnosis with tardive dyskinesia. Unfortunately, parakinesia was largely neglected by mainstream psychiatry to the point of being almost absent from the English-language literature. With the renewed interest in motor phenomena intrinsic to SSD, it was timely not only to raise awareness of parakinesia, but also to propose a scientifically usable definition for this phenomenon. Therefore, we conducted a Delphi consensus exercise with clinicians familiar with the concept of parakinesia. The original concept was separated into hyperkinetic parakinesia (HPk) as dyskinetic-like expressive movements and parakinetic psychomotricity (PPM), i.e., patient's departing from the patient's normal motion style. HPk prevails on the upper part of the face and body, resembling expressive and reactive gestures that not only occur inappropriately but also appear distorted. Abnormal movements vary in intensity depending on the level of psychomotor arousal and are thus abated by antipsychotics. HPk frequently co-occurs with PPM, in which gestures and mimics lose their naturalness and become awkward, disharmonious, stiff, mannered, and bizarre. Patients are never spontaneously aware of HPk or PPM, and the movements are never experienced as self-dystonic or self-alien. HPk and PPM are highly specific to endogenous psychoses, in which they are acquired and progressive, giving them prognostic value. Their differential diagnoses and correspondences with current international concepts are discussed.

Historical developments, hotspots, and trends in tardive dyskinesia research: a scientometric analysis of 54 years of publications

Background

Since being recognized as an important drug-induced clinical entity during the 1960s, tardive dyskinesia (TD) has generated an extensive body of research seeking to understand its clinical characteristics, epidemiology, pathophysiology and management. Modern scientometric approaches allow interactive visualization of large bodies of literature to identify trends and hotspots within knowledge domains. This study thus aimed to provide a comprehensive scientometric review of the TD literature.

Methods

Web of Science was searched for articles, reviews, editorials and letters with the term "tardive dyskinesia" in the title, abstract, or keywords through 12/31/2021. A total of 5,228 publications and 182,052 citations were included. Annual research output, prominent research areas, authors, affiliations and countries were summarized. VOSViewer and CiteSpace were used for bibliometric mapping and co-citation analysis. Structural and temporal metrics were used to identify key publications in the network.

Results

TD-related publications peaked in the 1990s, gradually declined after 2004, and showed a further small increase after 2015. The most prolific authors were Kane JM, Lieberman JA, and Jeste DV overall (1968-2021), and Zhang XY, Correll CU and Remington G in the last decade (2012-2021). The most prolific journal was the Journal of Clinical Psychiatry overall, and the Journal of Psychopharmacology in the last decade. Knowledge clusters in the 1960-1970s dealt with clinical and pharmacological characterization of TD. In the 1980s, epidemiology, clinical TD assessment, cognitive dysfunction and animal models predominated. During the 1990s, research diverged into pathophysiological studies, especially oxidative stress, and clinical trials on atypical antipsychotics, with a focus on clozapine and bipolar disorder. In the 1990-2000s, pharmacogenetics emerged. More recent clusters include serotonergic receptors, dopamine-supersensitivity psychosis, primary motor abnormalities of schizophrenia, epidemiology/meta-analyses, and advances in TD treatment, particularly vesicular monoamine transporter-2 inhibitors since 2017.

Conclusion

This scientometric review visualized the evolution of scientific knowledge on TD over more than five decades. These findings will be useful for researchers to find relevant literature when writing scientific articles, choosing appropriate journals, finding collaborators or mentors for research, and to understand the historical developments and emerging trends in TD research.

Impact of possible tardive dyskinesia on physical wellness and social functioning: results from the real-world RE-KINECT study

BACKGROUND

Tardive dyskinesia (TD) is a persistent and potentially disabling movement disorder associated with antipsychotic use. Data from RE-KINECT, a real-world study of antipsychotic-treated outpatients, were analyzed to assess the effects of possible TD on patient health and social functioning.

METHODS

Analyses were conducted in Cohort 1 (patients with no abnormal involuntary movements) and Cohort 2 (patients with possible TD per clinician judgment). Assessments included: EuroQoL's EQ-5D-5L utility (health); Sheehan Disability Scale (SDS) total score (social functioning); patient- and clinician-rated severity of possible TD ("none", "some", "a lot"); and patient-rated impact of possible TD ("none", "some", "a lot"). Regression models were used to analyze the following: associations between higher (worse) severity/impact scores and lower (worse) EQ-5D-5L utility (indicated by negative regression coefficients); and associations between higher (worse) severity/impact scores and higher (worse) SDS total score (indicated by positive regression coefficients).

RESULTS

In Cohort 2 patients who were aware of their abnormal movements, patient-rated TD impact was highly and significantly associated with EQ-5D-5L utility (regression coefficient: - 0.023, P < 0.001) and SDS total score (1.027, P < 0.001). Patient-rated severity was also significantly associated with EQ-5D-5L utility (- 0.028, P < 0.05). Clinician-rated severity was moderately associated with both EQ-5D-5L and SDS, but these associations were not statistically significant.

CONCLUSIONS

Patients were consistent in evaluating the impacts of possible TD on their lives, whether based on subjective ratings ("none", "some", "a lot") or standardized instruments (EQ-5D-5L, SDS). Clinician-rated severity of TD may not always correlate with patient perceptions of the significance of TD.

Pharmacokinetics, safety and tolerability of valbenazine in Korean CYP2D6 normal and intermediate metabolizers

Valbenazine is a selective vesicular monoamine transporter 2 (VMAT2) inhibitor approved for tardive dyskinesia treatment by the US Food and Drug Administration; its major active metabolite (NBI-98782) is a 45-fold more potent inhibitor of VMAT2 than the parent drug. This study aimed to evaluate the pharmacokinetics (PKs), safety, and tolerability and the effect of cytochrome P450 2D6 (CYP2D6) genotypes to the PKs after the administration of valbenazine in Korean participants. A randomized, double-blind, placebo-controlled, single- and multiple-dose study was conducted in healthy Korean male participants. The single-dose study was conducted for both 40 and 80 mg valbenazine and the multiple dose study was conducted for 40 mg. After a 1-week washout, the 40 mg dose group participants received valbenazine 40 mg or placebo once daily for 8 days. Serial blood samples were collected up to 96 h postdose for PK analysis. The CYP2D6 genotypes of the participants were retrospectively analyzed. A total of 50 participants were randomized, and 43 and 20 participants completed the single- and multiple-dose phases of the study, respectively. After single doses, the PK characteristics of valbenazine and its metabolites were similar between the 40 and 80 mg dose groups. After multiple doses, the mean accumulation ratios of valbenazine and NBI-98782 were ~1.6 and 2.4, respectively. Plasma concentrations of valbenazine and NBI-98782 were similar between CYP2D6 normal and intermediate metabolizers. Valbenazine was well-tolerated in healthy Koreans, and its PK characteristics were similar to results previously reported in Americans.

The Difficult Path to the Discovery of Novel Treatments in Psychiatric Disorders

CNS diseases, including psychiatric disorders, represent a significant opportunity for the discovery and development of new drugs and therapeutic treatments with the potential to have a significant impact on human health. CNS diseases, however, present particular challenges to therapeutic discovery efforts, and psychiatric diseases/disorders may be among the most difficult. With specific exceptions such as psychostimulants for ADHD, a large number of psychiatric patients are resistant to existing treatments. In addition, clinicians have no way of knowing which psychiatric patients will respond to which drugs. By definition, psychiatric diagnoses are syndromal in nature; determinations of efficacy are often self-reported, and drug discovery is largely model-based. While such models of psychiatric disease are amenable to screening for new drugs, whether cellular or whole-animal based, they have only modest face validity and, more importantly, predictive validity. Multiple academic, pharmaceutical industry, and government agencies are dedicated to the translation of new findings about the neurobiology of major psychiatric disorders into the discovery and advancement of novel therapies. The collaboration of these agencies provide a pathway for developing new therapeutics. These efforts will be greatly helped by recent advances in understanding the genetic bases of psychiatric disorders, the ongoing search for diagnostic and therapy-responsive biomarkers, and the validation of new animal models.

A new era in the diagnosis and treatment of tardive dyskinesia

Tardive dyskinesia (TD) is a heterogeneous, hyperkinetic movement disorder induced by dopamine-receptor blocking agents that presents a unique challenge in the treatment of psychosis. Although acceptance of TD as a serious consequence of antipsychotic treatment was resisted initially, subsequent research by many investigators in psychopharmacology contributed to a rich store of knowledge on many aspects of the disorder. While basic neuroscience investigations continue to deepen our understanding of underlying motor circuitry, past trials of potential treatments of TD focusing on a range of theoretical targets were often inconclusive. Development of newer antipsychotics promised to reduce the risk of TD compared to older drugs, but their improved tolerability unexpectedly enabled an expanding market that paradoxically both increased the absolute number of patients at risk and diminished attention to TD which was relegated to legacy status. Fortunately, development and approval of novel vesicular monoamine transporter inhibitors offered evidence-based symptomatic treatment of TD for the first time and rekindled interest in the disorder. Despite recent progress, many questions remain for future research including the mechanisms underlying TD, genetic predisposition, phenomenological diversity, whether new cases are reversible, how to implement best practices to prevent and treat TD, and whether the development of novel antipsychotics free of the risk of TD is attainable. We owe our patients the aspirational goal of striving for zero prevalence of persistent symptoms of TD in anyone treated for psychosis.

Treatable Hyperkinetic Movement Disorders Not to Be Missed

Hyperkinetic movement disorders are characterized by the presence of abnormal involuntary movements, comprising most notably dystonia, chorea, myoclonus, and tremor. Possible causes are numerous, including autoimmune disorders, infections of the central nervous system, metabolic disturbances, genetic diseases, drug-related causes and functional disorders, making the diagnostic process difficult for clinicians. Some diagnoses may be delayed without serious consequences, but diagnosis delays may prove detrimental in treatable disorders, ranging from functional disabilities, as in dopa-responsive dystonia, to death, as in Whipple's disease. In this review, we focus on treatable disorders that may present with prominent hyperkinetic movement disorders.

Amantadine in the treatment of Parkinson's disease and other movement disorders

The efficacy of amantadine in the symptomatic treatment of patients with Parkinson's disease, discovered serendipitously more than 50 years ago, has stood the test of time and the drug is still commonly used by neurologists today. Its pharmacological actions are unique in combining dopaminergic and glutamatergic properties, which account for its dual effect on parkinsonian signs and symptoms and levodopa-induced dyskinesias. Furthermore, amantadine has additional and less well-defined pharmacological effects, including on anticholinergic and serotonergic activity. Evidence from randomised controlled trials over the past 5 years has confirmed the efficacy of amantadine to treat levodopa-induced dyskinesias in patients with Parkinson's disease, and clinical studies have also provided support for its potential to reduce motor fluctuations. Other uses of amantadine, such as in the treatment of drug-induced parkinsonism, atypical parkinsonism, Huntington's disease, or tardive dyskinesia, lack a strong evidence base. Future trials should examine its role in the management of motor and non-motor symptoms in patients with early Parkinson's disease and those with other movement disorders.

Synthesis and analysis of dihydrotetrabenazine derivatives as novel vesicular monoamine transporter 2 inhibitors

Vesicular monoamine transporter 2 (VMAT2) is essential for synaptic transmission of all biogenic amines in the brain including serotonin, norepinephrine, histamine, and dopamine (DA). Given its crucial role in the neurophysiology and pharmacology of the central nervous system, VMAT2 is recognized as an important therapeutic target for various neurological disorders such as tardive dyskinesia (TD). Here, a novel series of dihydrotetrabenazine derivative analogs were designed and synthesized to evaluate their effects on [³H]dihydrotetrabenazine (DTBZ) binding and [³H]DA uptake at VMAT2. Of these analogs, compound 13e showed a high binding affinity for VMAT2 (IC₅₀ = 5.13 ± 0.16 nM) with excellent inhibition of [³H]DA uptake (IC₅₀ = 6.04 ± 0.03 nM) in striatal synaptosomes. In human liver microsomes, 13e was more stable (T_1/2 = 161.2 min) than other reported VMAT2 inhibitors such as DTBZ (T_1/2 = 119.5 min). In addition, 13e effectively inhibited the spontaneous locomotor activity (percent inhibition at 3 μmol/kg = 64.7%) in Sprague-Dawley rats. Taken together, our results indicate that 13e might be a promising lead compound for the development of novel treatments of TD.