Clinical management model for impulse control disorders in Parkinson's disease

Over the last decade, we have gained a better understanding of impulse control disorder in Parkinson's disease (PD-ICD), a medication complication in PD. Researchers were aware of its complexity and took efforts to learn more about its diagnostic and treatment possibilities. Nevertheless, clinical management for it is currently neglected. We conducted a narrative overview of literature published from 2012 to October 2023 on various aspects of clinical management for PD-ICD. A potential "susceptibility-catalytic-stress" model in the development of PD-ICD was proposed and a profile encoding predictors for PD-ICD was created. Based on these predictors, some methods for prediction were recently developed for better prediction, such as the polymorphic dopamine genetic risk score and the clinic-genetic ICD-risk score. A variety of treatment options, including dose reduction of dopamine receptor agonists (DAs), DAs removal, DAs switch, and add-on therapy, are investigated with inconsistent reports. Based on current findings, we developed a clinical management model prototype centered on prevention, consisting of prediction, prevention, follow-up and monitoring, therapy, and recurrence prevention, for clinical reference, and further proposed 4 key clinical management principles, including standardization, prediction centered, persistence, and whole course.

Tips and tricks in tremor treatment

Tremor, whether arising from neurological diseases, other conditions, or medication side effects, significantly impacts patients' lives. Treatment complexities necessitate clear algorithms and strategies. Levodopa remains pivotal for Parkinson's tremor, though response variability exists. Some dopamine agonists offer notable tremor reduction targeting D2 receptors. Propranolol effectively manages essential tremor and essential tremor plus (ET/ET +), sometimes with primidone for added benefits, albeit dose-dependent side effects. As reserve medications anticholinergics and clozapine are used for treatment of parkinsonian tremor, 1-Octanol and certain anticonvulsant drugs for tremor of other orign, especially ET. Therapies such as invasive deep brain stimulation and lesional focused ultrasound serve for resistant cases. A medication review is crucial for all forms of tremor, but it is particularly important if medication may have triggered the tremor. Sensor-based detection and non-drug interventions like wristbands and physical therapy broaden diagnostic and therapeutic horizons, promising future tremor care enhancements. Understanding treatment nuances is a key for tailored tremor management respecting patient needs and tolerability. Successful strategies integrate pharmacological, non-invasive, and technological modalities, aiming for optimal symptom control and improved quality of life.

Three paradoxes related to the mode of action of pramipexole: The path from D2/D3 dopamine receptor stimulation to modification of dopamine-modulated functions

Pramipexole, a D2/D3 dopamine receptor agonist, is used to treat the motor symptoms of Parkinson's disease, caused by degeneration of the dopaminergic nigrostriatal pathway. There are three paradoxes associated with its mode of action. Firstly, stimulation of D2/D3 receptors leads to neuronal inhibition, although pramipexole does not inhibit but promotes some dopamine-modulated functions, such as locomotion and reinforcement. Secondly, another dopamine-modulated function, arousal, is not promoted but inhibited by pramipexole, leading to sedation. Thirdly, pramipexole-evoked sedation is associated with an increase in pupil diameter, although sedation is expected to cause pupil constriction. To resolve these paradoxes, the path from stimulation of D2/D3 receptors to the modification of dopamine-modulated functions has been tracked. The functions considered are modulated by midbrain dopaminergic nuclei: locomotion - substantia nigra pars compacta (SNc), reinforcement/motivation - ventral tegmental area (VTA), sympathetic activity (as reflected in pupil function) - VTA; arousal - ventral periaqueductal grey (vPAG), with contributions from VTA and SNc. The application of genetics-based molecular techniques (optogenetics and chemogenetics) has enabled tracing the chains of neurones from the dopaminergic nuclei to their final targets executing the functions. The functional neuronal circuits linked to the D2/D3 receptors in the dorsal and ventral striata, stimulated by inputs from SNc and VTA, respectively, may explain how neuronal inhibition induced by pramipexole is translated into the promotion of locomotion, reinforcement/motivation and sympathetic activity. As the vPAG may increase arousal mainly by stimulating cortical D1 dopamine receptors, pramipexole would stimulate only presynaptic D2/D3 receptors on vPAG neurones, curtailing their activity and leading to sedation.

The Contribution of Type 2 Diabetes to Parkinson's Disease Aetiology

Type 2 diabetes (T2D) and Parkinson's disease (PD) are chronic disorders that have a significant health impact on a global scale. Epidemiological, preclinical, and clinical research underpins the assumption that insulin resistance and chronic inflammation contribute to the overlapping aetiologies of T2D and PD. This narrative review summarises the recent evidence on the contribution of T2D to the initiation and progression of PD brain pathology. It also briefly discusses the rationale and potential of alternative pharmacological interventions for PD treatment.

Impulse control disorders in Parkinson's disease patients treated with pramipexole and ropinirole: a systematic review and meta-analysis

BACKGROUND

This analysis is the first systematic review and meta-analysis assessing occurrences of ICD in PD patients treated with oral DAs: ropinirole (ROP) and pramipexole (PRX). This study compares the two oral DAs to a transdermal patch, rotigotine (RTG).

METHODS

We performed an extensive systematic search for eligible studies from PubMed, Embase, Cochrane Library, and Google Scholar. The data was analyzed by various software, including EndNote, Rayyan, PRISM, and RevMan. Two studies incorporating 658 patients collectively were assessed.

RESULTS

This meta-analysis shows a significant correlation between the usage of PRX (25.3%) or ROP (21.8%) and the development of ICD in PD patients. Compared to the transdermal patch, RTG, PRX was found to have a significant relative risk (P < 0.0001) of 3.46 (95% CI 2.07-5.76), and ROP was found to have a significant relative risk (P < 0.0001) of 2.98 (95% CI 1.77-5.02). The data collected shows RTG is approximately three times less likely to cause ICDs than oral PRX and ROP.

CONCLUSION

The present investigation provides insight into ICD occurrences with PRX, ROP, and RTG to allow physicians to make more informed decisions on risk versus reward when deciding how to treat a PD patient with these drugs. However, related to various disclosed limitations, our conclusion cannot provide definitive practice protocols.

Creative thinking and cognitive estimation in Parkinson's disease

BACKGROUND

Patients with Parkinson's disease (PD) have been reported to exhibit unusual bouts of creativity (e.g., painting, writing), in particular in the context of treatment with dopaminergic agents. Here we investigated divergent and convergent thinking thought to underlie creativity. In addition we assessed cognitive estimation.

METHOD

Twenty PD patients and 20 matched healthy control participants were subjected to the Guilford Alternate Uses task (divergent thinking), the remote associates task (convergent thinking) and two tests of cognitive estimation.

RESULTS

No group differences were found for the convergent thinking task, while the Guilford Alternate Uses task revealed a decreased number of correct responses and a reduced originality for PD patients. Originality in PD was correlated to total daily dose of dopaminergic medication. Moreover, both tasks of cognitive estimation showed an impairment in PD.

CONCLUSION

Only minor effects were found for psychometric indices of subprocesses of creative thinking, while estimation, relying on executive functioning, is impaired in PD. We suggest to take a product oriented view of creativity in further research on altered creative processes in PD.

Impulse control and related behavioral disorders (ICRD) in Idiopathic Parkinson's Disease treated with different dopamine agonists in Hong Kong: Is any dopamine agonist better?

Objective

To assess the incidence of Impulse control and related behavioral disorders (ICRD) in Chinese Idiopathic Parkinson Disease (IPD) patients treated with different dopamine agonists (DA), and their clinical characteristics and associated risk factors.

Methods

This was an observational cohort study based on clinical interviews and medical records of IPD patients treated with DA for >6 months in three hospitals in Hong Kong. The short version of Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP-S) was used to screen for ICRD. ICRD incidence among different DA, clinical characteristics and risk factors were examined.

Results

Incidence of ICRD was analyzed in 311 patients taking their first, single DA. 43 patients (13.8 %) developed ICRD. The mean duration of IPD was 8.5 ± 5.6 years and median HY stage was 2.5. Bromocriptine and rotigotine users had lower ICRD incidence rate. Both pramipexole [adjusted HR 7.28 (2.46-21.54), p < 0.001] and ropinirole [adjusted HR 6.53 (2.67-15.99), p < 0.001] were independently associated with higher risk of ICRD compared to bromocriptine in multivariate analysis. Similarly, pramipexole and ropinirole appeared to carry higher risk compared to rotigotine but did not reach statistical significance. Male [adjusted HR 2.24 (1.07-4.72), p = 0.033], younger IPD onset [adjusted HR 2.99 (1.44-6.19) for onset < 50 year, p = 0.003] and history of psychiatric disorders [adjusted HR 2.80 (1.39-5.62), p = 0.004] were other independent risk factors.

Conclusion

Bromocriptine and probably rotigotine carried a lower ICRD risk compared to pramipexole and ropinirole.

Aripiprazole and Other Third-Generation Antipsychotics as a Risk Factor for Impulse Control Disorders: A Systematic Review and Meta-Analysis

BACKGROUND

Increasing evidence suggests an association between third-generation antipsychotics (TGAs) and impulse control disorders (ICDs). This is thought to be due to their partial agonism of dopamine receptors. However, neither the relative nor absolute risks of ICDs in those prescribed TGAs are well established. To inform clinical practice, this systematic review and meta-analysis summarizes and quantifies the current evidence for an association.

METHODS

An electronic search of Medline, PsychINFO, EMBASE, and the Cochrane Clinical Trials Database was undertaken from database inception to November 2022. Three reviewers screened abstracts and reviewed full texts for inclusion. A random-effects meta-analysis was conducted with eligible studies.

RESULTS

A total of 392 abstracts were retrieved, 214 remained after duplicates were removed. Fifteen full texts were reviewed, of which 8 were included. All 8 studies found that TGAs were associated with increased probability of ICDs. Risk of bias was high or critical in 7 of 8 studies. Three studies were included in the pooled analysis for the primary outcome, 2 with data on each of aripiprazole, cariprazine, and brexpiprazole. Exposure to TGAs versus other antipsychotics was associated with an increase in ICDs (pooled odds ratio, 5.54; 2.24-13.68). Cariprazine and brexpiprazole were significantly associated with ICDs when analyzed individually. Aripiprazole trended toward increased risk, but very wide confidence intervals included no effect.

CONCLUSIONS

Third-generation antipsychotics were associated with increased risk of ICDs in all studies included and pooled analysis. However, the risk of bias is high, confidence intervals are wide, and the quality of evidence is very low for all TGAs examined.

Practical use of apomorphine infusion in Parkinson's disease: lessons from the TOLEDO study and clinical experience

Subcutaneous apomorphine infusion is a device-aided therapy for Parkinson's disease that can be considered when motor fluctuations become persistent and are no longer adequately controlled by oral/transdermal medication. Apomorphine infusion is less invasive than enteral levodopa, deep brain stimulation or focused ultrasound, and is often indicated even when neurosurgical approaches are contraindicated. This article aims to provide practical guidance for doctors and nurses initiating and treating patients with apomorphine infusion, and is based on both trial data and clinical experience from movement disorders specialists. A post hoc analysis of data from the TOLEDO randomized clinical trial of apomorphine infusion was conducted along with an analysis of 'real world' experience from 13 movement disorders specialists using a questionnaire that focused on starting patients on apomorphine infusion. Practical guidelines for starting treatment with apomorphine infusion are provided taking into consideration the regional disparities in healthcare. Apomorphine infusion is straightforward to administer but to be successful it requires concordance from the patient and family, and clinical support from an experienced team of doctors and nurses, particularly in the early months of treatment.

Adopting the Rumsfeld approach to understanding the action of levodopa and apomorphine in Parkinson's disease

Dopaminergic therapies dominate the treatment of the motor and non-motor symptoms of Parkinson's disease (PD) but there have been no major advances in therapy in many decades. Two of the oldest drugs used appear more effective than others-levodopa and apomorphine-but the reasons for this are seldom discussed and this may be one cause for a lack of progress. This short review questions current thinking on drug action and looks at whether adopting the philosophy of ex-US Secretary of State Donald Rumsfeld reveals 'unknown' aspects of the actions of levodopa and apomorphine that provide clues for a way forward. It appears that both levodopa and apomorphine have a more complex pharmacology than classical views would suggest. In addition, there are unexpected facets to the mechanisms through which levodopa acts that are either forgotten as 'known unknowns' or ignored as 'unknown unknowns'. The conclusion reached is that we may not know as much as we think about drug action in PD and there is a case for looking beyond the obvious.

Impulse Control Disorders in the Polish Population of Patients with Parkinson's Disease

Background and Objectives: Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the world. It is characterized by the presence of not only typical motor symptoms but also several less known and aware non-motor symptoms (NMS). The group of disorders included in the NMS is Impulse Control Disorders (ICDs). ICDs are a group of disorders in which patients are unable to resist temptations and feel a strong, pressing desire for specific activities such as gambling, hypersexuality, binge eating, and compulsive buying. The occurrence of ICDs is believed to be associated primarily with dopaminergic treatment, with the use of dopamine agonists (DA), and to a lesser extent with high doses of L-dopa. The aim of our study was to develop a profile of Polish ICDs patients and assess the frequency of occurrence of ICDs, as well as determine the risk factors associated with these disorders against the background of the PD population from other countries. Materials and Methods: Our prospective study included 135 patients with idiopathic PD who were hospitalized between 2020 and 2022 at the Neurological Department of University Central Hospital in Katowice. In the assessment of ICDs, we used the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP). Other scales with which we assessed patients with PD were as follows: MDS-UPDRS part III and modified Hoehn-Yahr staging. Clinical data on age, gender, disease duration and onset, motor complications, and medications were collected from electronic records. Results: ICDs were detected in 27.41% of PD patients (binge eating in 12.59%, hypersexuality in 11.11%, compulsive buying in 10.37%, and pathological gambling occurred in only 5.19% of patients. In total, 8.89% had two or more ICDs). The major finding was that ICDs were more common in patients taking DA than in those who did not use medication from this group (83.78% vs. 54.07%, respectively; p = 0.0015). Patients with ICDs had longer disease duration, the presence of motor complications, and sleep disorders. An important finding was also a very low detection of ICDs in a routine medical examination; only 13.51% of all patients with ICDs had a positive medical history of this disorder. Conclusions: ICDs are relatively common in the population of Polish PD patients. The risk factors for developing ICDs include longer duration of the disease, presence of motor complications, sleep disorders, and use of DA and L-dopa. Due to the low detectability of ICDs in routine medical history, it is essential for physicians to pay more attention to the possibility of the occurrence of these symptoms, especially in patients with several risk factors. Further prospective studies on a larger group of PD patients are needed to establish a full profile of Polish PD patients with ICDs.

Role of dopamine agonists in Parkinson's disease therapy

Dopamine agonists are an important component of Parkinson's therapy. When weighing up the various therapy options, therapy with levodopa has recently been increasingly preferred due to its stronger efficacy and the ostensibly lower rate of side effects. The advantage of the lower incidence of motor complications during therapy with dopamine agonists was neglected. The occurrence of side effects can be explained by the different receptor affinity to the individual dopaminergic and non-dopaminergic receptors of the individual dopamine agonists. However, the different affinity to individual receptors also explains the different effect on individual Parkinson symptoms and can, therefore, contribute to a targeted use of the different dopamine agonists. Since comparative studies on the differential effect of dopamine agonists have only been conducted for individual substances, empirical knowledge of the differential effect is of great importance. Therefore, the guidelines for the treatment of Parkinson's disease do not consider the differential effect of the dopamine agonists. The historical consideration of dopamine agonists within Parkinson's therapy deserves special attention to be able to classify the current discussion about the significance of dopamine agonists.

Pharmacological Modulation of Temporal Discounting: A Systematic Review

Temporal discounting is a phenomenon where a reward loses its value as a function of time (e.g., a reward is more valuable immediately than when it delays in time). This is a type of intertemporal decision-making that has an association with impulsivity and self-control. Many pathologies exhibit higher discounting rates, meaning they discount more the values of rewards, such as addictive behaviors, bipolar disorder, attention-deficit/hyperactivity disorders, social anxiety disorders, and major depressive disorder, among others; thus, many studies look for the mechanism and neuromodulators of these decisions. This systematic review aims to investigate the association between pharmacological administration and changes in temporal discounting. A search was conducted in PubMed, Scopus, Web of Science, Science Direct and Cochrane. We used the PICO strategy: healthy humans (P-Participants) that received a pharmacological administration (I-Intervention) and the absence of a pharmacological administration or placebo (C-Comparison) to analyze the relationship between the pharmacological administration and the temporal discounting (O-outcome). Nineteen studies fulfilled the inclusion criteria. The most important findings were the involvement of dopamine modulation in a U-shape for choosing the delayed outcome (metoclopradime, haloperidol, and amisulpride). Furthermore, administration of tolcapone and high doses of d-amphetamine produced a preference for the delayed option. There was a time-dependent hydrocortisone effect in the preference for the immediate reward. Thus, it can be concluded that dopamine is a crucial modulator for temporal discounting, especially the D2 receptor, and cortisol also has an important time-dependent role in this type of decision. One of the limitations of this systematic review is the heterogeneity of the drugs used to assess the effect of temporal discounting.

Ultra-high-field pharmacological functional MRI of dopamine D1 receptor-related interventions in anesthetized rats

The dopamine D1 receptor (D1R) is associated with schizophrenia, Parkinson's disease, and attention deficit hyperactivity disorder. Although the receptor is considered a therapeutic target for these diseases, its neurophysiological function has not been fully elucidated. Pharmacological functional MRI (phfMRI) has been used to evaluate regional brain hemodynamic changes induced by neurovascular coupling resulting from pharmacological interventions, thus phfMRI studies can be used to help understand the neurophysiological function of specific receptors. Herein, the blood oxygenation level-dependent (BOLD) signal changes associated with D1R action in anesthetized rats was investigated by using a preclinical ultra-high-field 11.7-T MRI scanner. PhfMRI was performed before and after administration of the D1-like receptor agonist (SKF82958), antagonist (SCH39166), or physiological saline subcutaneously. Compared to saline, the D1-agonist induced a BOLD signal increase in the striatum, thalamus, prefrontal cortex, and cerebellum. At the same time, the D1-antagonist reduced the BOLD signal in the striatum, thalamus, and cerebellum by evaluating temporal profiles. PhfMRI detected D1R-related BOLD signal changes in the brain regions associated with high expression of D1R. We also measured the early expression of c-fos at the mRNA level to evaluate the effects of SKF82958 and isoflurane anesthesia on neuronal activity. Regardless of the presence of isoflurane anesthesia, c-fos expression level was increased in the region where positive BOLD responses were observed with administration of SKF82958. These findings demonstrated that phfMRI could be used to identify the effects of direct D1 blockade on physiological brain functions and also for neurophysiological assessment of dopamine receptor functions in living animals.

Performance on the balloon analogue risk task and anticipatory response inhibition task is associated with severity of impulse control behaviours in people with Parkinson's disease

Dopamine agonist medication is one of the largest risk factors for development of problematic impulse control behaviours (ICBs) in people with Parkinson's disease. The present study investigated the potential of dopamine gene profiling and individual performance on impulse control tasks to explain ICB severity. Clinical, genetic and task performance data were entered into a mixed-effects linear regression model for people with Parkinson's disease taking (n = 50) or not taking (n = 25) dopamine agonist medication. Severity of ICBs was captured via the Questionnaire for Impulsive-compulsive disorders in Parkinson's disease Rating Scale. A cumulative dopamine genetic risk score (DGRS) was calculated for each participant from variance in five dopamine-regulating genes. Objective measures of impulsive action and impulsive choice were measured on the Anticipatory Response Inhibition Task and Balloon Analogue Risk Task, respectively. For participants on dopamine agonist medication, task performance reflecting greater impulsive choice (p = 0.014), and to a trend level greater impulsive action (p = 0.056), as well as a longer history of DA medication (p < 0.001) all predicted increased ICB severity. DGRS however, did not predict ICB severity (p = 0.708). No variables could explain ICB severity in the non-agonist group. Our task-derived measures of impulse control have the potential to predict ICB severity in people with Parkinson's and warrant further investigation to determine whether they can be used to monitor ICB changes over time. The DGRS appears better suited to predicting the incidence, rather than severity, of ICBs on agonist medication.

Exploring the underlying mechanisms of drug-induced impulse control disorders: a pharmacovigilance-pharmacodynamic study

INTRODUCTION

Impulse control disorders (e.g. pathological gambling, hypersexuality) may develop as adverse reactions to drugs. Pathogenetic hypotheses have mainly focused on D3-receptor agonism, and switching to alternatives with different pharmacologic mechanisms represents a common management strategy. Nonetheless, treatment failure is common and gaining pathophysiological insights is needed.

AIM

We aimed to identify targets potentially contributing to pathologic impulsivity.

METHOD

We performed a pharmacovigilance-pharmacodynamic study on dopamine agonists and antipsychotics using the Food and Drug Administration Adverse Event Reporting System (January 2004-December 2021). We estimated disproportionate reporting using the Bayesian information component. Using online public databases (IUPHAR, ChEMBL, PDSP, DrugBank), we calculated drug occupancies. To identify the targets potentially contributing to impulsivity, we fitted univariate regression models interpolating information components and occupancies within dopamine agonists and antipsychotics. Sensitivity analyses were performed to check for the robustness of the results.

RESULTS

Among 19 887 reports of impulsivity, 5898 recorded an antipsychotic, and 3100 a dopamine agonist. The more robust signals concerned aripiprazole (N = 3091; median information component [95% confidence interval] = 4.51[4.45-4.55]) and brexpiprazole (229; 4.00[3.78-4.16]) for antipsychotics, pergolide (105; 5.82[5.50-6.06]) and pramipexole (2009; 5.43[5.36-5.48]) for dopamine agonists. Robust, significant positive associations between drug occupancy and impulsivity reporting were found for D3 within dopamine agonists (beta = 1.52; P-value = 0.047) and 5-HT1a within antipsychotics (1.92, 0.029).

CONCLUSION

Our results supported the role of D3-receptor agonism in inducing impulsivity in dopamine receptor agonists and identified a potential role of 5-HT1a receptor agonism in antipsychotics. Investigating these receptors may drive towards a better management of drug-induced impulsivity.

The Role of Aromatase Inhibitors in Male Prolactinoma

BACKGROUND

dopamine agonists are the recommended treatment for male prolactinomas, but some patients may develop dopamine-agonist-resistant hyperprolactinemia, leading to persistent hypogonadism that requires treatment with testosterone. However, testosterone replacement therapy may be associated with a decrease in the efficacy of dopamine agonists due to the aromatization of testosterone to estradiol, which can stimulate the proliferation and hyperplasia of lactotroph cells in the pituitary, inducing resistance to dopamine agonists.

OBJECTIVE

this paper systematically reviewed the role of aromatase inhibitors for men with prolactinoma and dopamine-agonist-resistant or persistent hypogonadism following treatment.

METHOD

we performed a systematic review of all studies (according to PRISMA guidelines), assessing the role of aromatase inhibitors, including anastrozole and letrozole, for male prolactinoma. An English-language search for relevant studies was conducted on PubMed from its inception to 1 December 2022. The reference lists of the relevant studies were also reviewed.

RESULTS

our systematic review identified six articles (nine patients), including five case reports and a single case series, on the use of aromatase inhibitors for male prolactinomas. Reducing estrogen levels with an aromatase inhibitor improved sensitivity to dopamine agonists, as the addition of anastrozole or letrozole improves the control of prolactin levels and may lead to the shrinkage of tumors.

CONCLUSION

aromatase inhibitors are of potential value to patients with dopamine-agonist-resistant prolactinoma, or when hypogonadism persists while using high-dose dopamine agonists.

Screening for impulse control disorders in Parkinson's disease and dopamine agonist use: a study of pharmacokinetic and psychological risk factors

INTRODUCTION

Dopamine agonist (DA) use is considered the main risk factor for impulse control disorder (ICD) development in Parkinson's disease (PD). Besides DAs, personality traits and cognitive features may represent risk factors for ICDs. The primary aim of this study was to investigate differences in DA plasma concentrations in PD patients with and without a positive screening for ICDs according to validated tools. The secondary aim was to compare the psychological profile between ICD positive and negative screened patients.

METHODS

PD patients receiving chronic DA therapy were screened for ICDs according to the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP). Blood samples for measurement of DA (pramipexole, ropinirole, rotigotine) trough plasma concentrations were drawn in the morning, at mean 16-19 h from the last DA dose. Patients' psychological profile was investigated by Millon Clinical Multiaxal Inventory III and Barratt Impulsiveness Scale (BIS-11).

RESULTS

One hundred and five PD patients were enrolled. Forty-one patients (39%) were QUIP positive, mainly for binge eating and hobbyism. Median plasma concentrations of pramipexole (n = 71, 66%), ropinirole (n = 21, 19%), and rotigotine (n = 16, 15%) were similar between QUIP positive and negative patients. QUIP positive patients showed higher motor impulsiveness (p = 0.04) and tended to higher total impulsiveness (p = 0.05).

CONCLUSION

This is the first prospective study to evaluate the relationship between DA plasma concentrations and ICDs risk in PD patients. DA plasma levels were overlapping between QUIP positive and negative patients. BIS-11, particularly the motor impulsiveness subscale, might be a useful screening tool in PD patients eligible for DA therapy.

Advances in the Therapeutic Use of Non-Ergot Dopamine Agonists in the Treatment of Motor and Non-Motor Symptoms of Parkinson's Disease

Dopamine (DA) agonists, as an excellent dopamine replacement therapy for patients with early and advanced Parkinson's disease (PD), play a vital role in controlling motor and several nonmotor symptoms. Besides, the application of DA agonists may delay levodopa therapy and the associated risk of motor complications. Indeed, each DA agonist has unique pharmacokinetic and pharmacodynamic characteristics and therefore has different therapeutic efficacy and safety profile. The comorbidities, significant non-motor manifestations, concomitant medications, and clinical features of PD individuals should guide the selection of a specific DA agonist to provide a more patient-tailored treatment option. Thorough knowledge of DA agonists helps clinicians better balance clinical efficacy and side effects. Therefore, this review refers to recent English-written articles on DA agonist therapy for PD patients and summarizes the latest findings on non-ergot DA agonists as well as the advantages and disadvantages of each compound to help clinicians in the selection of a specific DA agonist. In addition, novel D1/D5 partial agonists and new formulations of DA agonists are also discussed.

Drug-Induced Gambling Disorder: Epidemiology, Neurobiology, and Management

Problematic gambling has been suggested to be a possible consequence of dopaminergic medications used mainly in neurological conditions, i.e. pramipexole and ropinirole, and possibly by one antipsychotic compound, aripiprazole. Patients with Parkinson's disease, restless legs syndrome and other conditions potentially treated with dopamine agonists, as well as patients treated for psychotic disorders, are vulnerable patient groups with theoretically increased risk of developing gambling disorder (GD), for example due to higher rates of mental ill-health in these groups. The aim of the present paper is to review the epidemiological, clinical, and neurobiological evidence of the association between dopaminergic medications and GD, and to describe risk groups and treatment options. The neurobiology of GD involves the reward and reinforcement system, based mainly on mesocorticolimbic dopamine projections, with the nucleus accumbens being a crucial area for developing addictions to substances and behaviors. The addictive properties of gambling can perhaps be explained by the reward uncertainty that activates dopamine signaling in a pathological manner. Since reward-related learning is mediated by dopamine, it can be altered by dopaminergic medications, possibly leading to increased gambling behavior and a decreased impulse control. A causal relationship between the medications and GD seems likely, but the molecular mechanisms behind this association have not been fully described yet. More research is needed in order to fully outline the clinical picture of GD developing in patient groups with dopaminergic medications, and data are needed on the differentiation of risk in different compounds. In addition, very few interventional studies are available on the management of GD induced by dopaminergic medications. While GD overall can be treated, there is need for treatment studies testing the effectiveness of tapering of the medication or other gambling-specific treatment modalities in these patient groups.

The World Federation of Societies of Biological Psychiatry guidelines on the assessment and pharmacological treatment of compulsive sexual behaviour disorder

OBJECTIVES

The current guidelines aim to evaluate the role of pharmacological agents in the treatment of patients with compulsive sexual behaviour disorder (CSBD). They are intended for use in clinical practice by clinicians who treat patients with CSBD.

METHODS

An extensive literature search was conducted using the English-language-literature indexed on PubMed and Google Scholar without time limit, supplemented by other sources, including published reviews.

RESULTS

Each treatment recommendation was evaluated with respect to the strength of evidence for its efficacy, safety, tolerability, and feasibility. Psychoeducation and psychotherapy are first-choice treatments and should always be conducted. The type of medication recommended depended mainly on the intensity of CSBD and comorbid sexual and psychiatric disorders. There are few randomised controlled trials. Although no medications carry formal indications for CSBD, selective-serotonin-reuptake-inhibitors and naltrexone currently constitute the most relevant pharmacological treatments for the treatment of CSBD. In cases of CSBD with comorbid paraphilic disorders, hormonal agents may be indicated, and one should refer to previously published guidelines on the treatment of adults with paraphilic disorders. Specific recommendations are also proposed in case of chemsex behaviour associated with CSBD.

CONCLUSIONS

An algorithm is proposed with different levels of treatment for different categories of patients with CSBD.

Impulse control disorders in hyperprolactinemic patients on dopamine agonist therapy

Dopamine agonists (DAs) represent a mainstay of therapy for hyperprolactinemia and prolactinomas. The widespread use of DAs, including bromocriptine, cabergoline and (in some countries) quinagolide, has led to the emergence and recognition of impulse control disorders (ICDs) that may occur in association with DA therapy.Such ICDs include pathological gambling, compulsive shopping, hypersexuality and punding (the performance of repetitive tasks), among others. These manifestations can lead to substantial harms to patients and their families, if left undiagnosed and untreated. Several risk factors that may increase the risk of ICDs have been proposed, including younger age, male gender, smoking and alcohol use and history of depression.The diagnosis of ICDs in hyperprolactinemic patients treated with DAs requires a high index of suspicion and a systematic approach, using available screening questionnaires. However, it should be noted that available test instruments, including questionnaires and computerized tasks, have not been validated specifically in hyperprolactinemic patients. Hyperprolactinemic patients who develop ICDs should be withdrawn from DA therapy or, at a minimum, undergo a DA dose reduction, and considered for psychiatric consultation and cognitive behavioral therapy. However, the role of psychopharmacotherapy in hyperprolactinemic patients with ICDs remains incompletely characterized.Patient counseling regarding the risk of ICDs occurring in association with DA therapy, early detection and prompt intervention may mitigate potential harms associated with ICDs. Additional studies are needed to fully characterize risk factors, underlying mechanisms and identify effective therapies for ICDs in patients with hyperprolactinemia receiving DAs.

Impulse Control Disorders by Dopamine Partial Agonists: A Pharmacovigilance-Pharmacodynamic Assessment Through the FDA Adverse Event Reporting System

BACKGROUND

The dopaminergic partial agonism of the so-called third-generation antipsychotics (TGAs; aripiprazole, brexpiprazole, cariprazine) is hypothesized to cause impulse control disorders (ICDs). Relevant warnings by the Food and Drug Administration (FDA) were posted on aripiprazole (2016) and brexpiprazole (2018). Our study investigated the FDA Adverse Event Reporting System and the pharmacodynamic CHEMBL database to further characterize TGA-induced ICDs.

METHODS

We downloaded and pre-processed the FDA Adverse Event Reporting System up to December 2020. We adapted Bradford Hill criteria to assess each TGA's -and secondarily other antipsychotics'-causal role in inducing ICDs (pathological gambling, compulsive shopping, hyperphagia, hypersexuality), accounting for literature and disproportionality. ICD clinical features were analyzed, and their pathogenesis was investigated using receptor affinities.

RESULTS

A total of 2708 reports of TGA-related ICDs were found, primarily recording aripiprazole (2545 reports, 94%) among the drugs, and gambling (2018 reports, 75%) among the events. Bradford-Hill criteria displayed evidence for a causal role of each TGA consistent across subpopulations and when correcting for biases. Significant disproportionalities also emerged for lurasidone with compulsive shopping, hyperphagia, and hypersexuality, and olanzapine and ziprasidone with hyperphagia. Time to onset varied between days and years, and positive dechallenge was observed in 20% of cases. Frequently, co-reported events were economic (50%), obsessive-compulsive (44%), and emotional conditions (34%). 5-Hydroxytryptamine receptor type 1a agonism emerged as an additional plausible pathogenetic mechanism.

CONCLUSIONS

We detected an association between TGAs and ICDs and identified a new signal for lurasidone. ICD characteristics are behavior specific and may heavily impact on life. The role of 5-Hydroxytryptamine receptor type 1a agonism should be further explored.

Impulse control disorders associated with dopaminergic drugs: A disproportionality analysis using vigibase

BACKGROUND

Dopamine receptor agonist drugs, which are used, for example, to treat Parkinson's disease (PD), increase the risk for impulse control disorders (ICDs), potentially resulting in devastating psychosocial consequences. It is unknown whether other drugs with dopaminergic properties also increase the risk for ICDs. This study assesses the disproportionality of reporting ICDs between drugs with dopaminergic properties and selected non-dopaminergic drugs.

METHODS

A case/non-case disproportionality analysis was performed, using data from VigiBase (1968-2020). Reports on ICDs as suspected adverse drug reactions (ADRs) were cases (n=852), and those with ADRs other than ICDs were non-cases (n=281,720). Relative reporting frequencies were expressed as adjusted reporting odds ratios (aRORs). Within the dopamine receptor agonists, the relationship between reporting odds ratios and dopamine receptor occupancy was explored.

RESULTS

A high disproportionality was found for reporting ICDs for all dopaminergic drugs (aROR 20.4 [95% CI 17.4-24.1]) compared to non-dopaminergic drugs. In pharmacotherapeutic subgroups, a high disproportionality was found for primary dopaminergic agents used in PD (aROR 52.1 [95% CI 44.1-61.5]), and to a lesser extent for ADHD psychostimulants and antidepressants (aROR 5.8 [95% 4.1-8.3] and aROR 3.9 [95% CI 2.9-5.6], respectively). There was no difference in reporting by consumers and healthcare professionals. The highest disproportionality was found for the dopamine receptor agonists pramipexole and ropinirole.

CONCLUSIONS

A signal of disproportion in ICD occurrence was found among all investigated drugs with dopaminergic properties, highlighting the importance of counselling and monitoring for ICDs when prescribing dopaminergic drugs.

The steroidogenic inhibitor finasteride reverses pramipexole-induced alterations in probability discounting

Pramipexole is a potent agonist of D₃ and D₂ dopamine receptors, currently approved for clinical use in Parkinson's disease (PD) and restless leg syndrome. Several studies have shown that pramipexole significantly increases the risk of pathological gambling and impulse-control disorders. While these iatrogenic complications can impose a severe social and financial burden, their treatment poses serious clinical challenges. Our group previously reported that the steroidogenic inhibitor finasteride reduced pathological gambling severity in PD patients who developed this complication following pramipexole treatment. To study the mechanisms underlying these effects, here we tested the impact of finasteride in a rat model of pramipexole-induced alterations of probability discounting. We previously showed that, in rats exposed to low doses of the monoamine-depleting agent reserpine (1mg/kg/day, SC), pramipexole (0.3mg/kg/day, SC) increased the propensity to engage in disadvantageous choices. This effect was paralleled by a marked D₃ receptor upregulation in the nucleus accumbens. First, we tested how finasteride (25-50mg/kg, IP) intrinsically affects probability discounting. While the highest dose of finasteride produced a marked lack of interest in lever pressing (manifested as a significant increase in omissions), the 25mg/kg (IP) dose did not intrinsically modify probability discounting. However, this finasteride regimen significantly reduced the adverse effects of reserpine and pramipexole in probability discounting by diminishing rats' propensity to engage in highly disadvantageous probabilistic choices. The same regimen also reversed the upregulation of D₃ receptors in the nucleus accumbens induced by reserpine and pramipexole. These findings confirm that finasteride opposes the impulsivity caused by pramipexole and suggest that this effect may be underpinned by a normalizing effect on D₃ receptor expression in the nucleus accumbens.

Current concepts in treating mild cognitive impairment in Parkinson's disease

Impairment in various aspects of cognition is recognized as an important non-motor symptom of Parkinson's disease (PD). Mild cognitive impairment in PD (PD-MCI) is common in non-demented PD patients and is often associated with severity of motor symptoms, disease duration and increasing age. Further, PD-MCI can have a significant negative effect on performance of daily life activities and may be a harbinger of development of PD dementia. Thus, there is significant interest in developing therapeutic strategies to ameliorate cognitive deficits in PD and improve cognitive functioning of PD patients. However, due to significant questions that remain regarding the pathophysiology of cognitive dysfunction in PD, remediation of cognitive dysfunction in PD has proven difficult. In this paper, we will focus on PD-MCI and will review some of the current therapeutic approaches being taken to try to improve cognitive functioning in patients with PD-MCI.

[Relevance of COMT inhibitors in the treatment of motor fluctuations]

Catechol O‑methyltransferase (COMT) inhibitors have been established in the treatment of Parkinson's disease for more than 20 years. They are considered the medication of choice for treating motor fluctuations. The available COMT inhibitors, entacapone, opicapone and tolcapone, differ pharmacokinetically in terms of their half-lives with implications for the dose frequency, in their indication requirements and in their spectrum of side effects, including diarrhea and yellow discoloration of urine. Many patients with motor fluctuations are currently not treated with COMT inhibitors and are, therefore, unlikely to receive individually optimized drug treatment. This manuscript summarizes the results of a working group including several Parkinson's disease experts, in which the value of COMT inhibitors was critically discussed.

Validation of the Chinese Version of the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease

Background: Impulse control and related disorders (ICRDs) have gained recognition as a severe complication of Parkinson's disease (PD) and are connected to poor quality of life and devastating financial and social problems. This study aimed to evaluate the usefulness of the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease (QUIP) and estimate the risk factors for ICRDs in Chinese patients with PD. Methods: 207 PD patients were assessed using the QUIP and evaluated for PD motor and nonmotor symptoms. ICRDs were diagnosed via interviews of patients or their caregivers, and the clinical characteristics of patients with and without ICRDs were compared. Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the C-QUIP were 95.0, 83.4, 38.0, 99.4, and 84.5%. The prevalence of each disorder among participants diagnosed via interview was pathological gambling (0.5%), hypersexuality (1.9%), compulsive shopping (1.0%), binge eating (3.9%), hobbyism (1.9%), punding (0.5%), walkabout (0.5%), and dopamine dysregulation syndrome (2.9%). PD patients with ICRDs had longer PD duration, higher Hoehn and Yahr stage, Non-Motor Symptoms Scale (NMSS), and Hamilton-Depression Rating Scale (HAMD). Also, they received a larger total daily levodopa equivalent dose (LED), levodopa dosage, and dopamine agonist only LED (DA-LED) than did PD patients without ICRDs. Conclusions: Given its psychometric properties, the C-QUIP is a valid and rapid screening instrument for assessing of ICRDs in PD patients. Higher Hoehn and Yahr staging, NMSS and HAMD scores, a larger mean LED and levodopa dosage are risk factors for ICRDs.

The prevalence of impulsive compulsive behaviors in patients treated with apomorphine infusion: a retrospective analysis

BACKGROUND

Impulsive compulsive behaviors (ICBs) can affect a significant number of Parkinson's disease (PD) patients.

OBJECTIVE

We have studied brain samples from a brain bank of PD patients who received apomorphine via continuous infusion in life to assess the prevalence and outcome of ICBs.

METHODS

A search on the Queen Square Brain Bank (QSBB) database for cases donated from 2005 to 2016 with a pathological diagnosis of idiopathic PD was conducted. Notes of all donors who used apomorphine via continuous infusion for at least three months were reviewed. Clinical and demographic data were collected, as well as detailed information on treatment, prevalence and outcomes of ICBs.

RESULTS

193 PD cases, 124 males and 69 females, with an average age at disease onset of 60.2 years and average disease duration of 17.2 years were reviewed. Dementia occurred in nearly half of the sample, depression in one quarter, and dyskinesias in a little over 40%. The prevalence of ICBs was 14.5%. Twenty-four individuals used apomorphine infusion for more than three months. Patients on apomorphine had younger age at disease onset, longer disease duration, and higher prevalence of dyskinesias. The prevalence of de novo ICB cases among patients on apomorphine was 8.3%. Apomorphine infusion was used for an average of 63.1 months on an average maximum dose of 79.5 mg per day. Ten patients remained on apomorphine until death.

CONCLUSIONS

Apomorphine can be used as an alternative treatment for patients with previous ICBs as it has low risk of triggering recurrence of ICBs.

Analysis of Impulse Control Disorders (ICDs) and Factors Associated with Their Development in a Parkinson's Disease Population

Parkinson's Disease (PD) is a neurodegenerative disease in which non-motor symptoms may appear before motor phenomena, which include Impulse Control Disorders (ICDs). The objective of this study is to identify factors associated with the development of ICDs in PD. An analytical, cross-sectional study was conducted using clinical records from patients diagnosed with PD, both genders, from 40 to 80 years old. Clinical and demographic data were collected: 181 patients were recruited; 80 of them showed PD and ICDs, and they constituted the study group, whereas 101 patients with PD without ICDs constituted the control reference group. The duration of PD was longer in the group with ICDs (p < 0.008), and all patients showed at least one ICD: binge eating (61.29%), compulsive shopping (48.75%), hypersexuality (23.75%), gambling behavior (8.75%), and punding (3.75%). After logistic regression analysis, only the use of dopamine agonists remained associated with ICDs (p < 0.001), and the tremorgenic form was suggested to be a protective factor (p < 0.001). Positive associations were observed between the rigid-akinetic form and compulsive shopping (p < 0.007), between male and hypersexuality (p < 0.018), and between dopamine agonists and compulsive shopping (p < 0.004), and negative associations were observed between motor fluctuations and compulsive shopping (p < 0.031), between Deep Brain Stimulation and binge eating (p < 0.046), and between levodopa consumption and binge eating (p < 0.045). Binge eating, compulsive shopping, and hypersexuality were the most frequent ICDs. Complex forms and motor complications of PD were associated with the development of ICDs.

Do cariprazine and brexpiprazole cause impulse control symptoms? A case/non-case study

Aripiprazole has been associated with impulse control symptoms (ICS). Recently, two drugs with similar pharmacological features have become available: cariprazine and brexpiprazole. All of them interact with the D₃ receptor, which plays a role in cerebral circuits involved in reward pathways. The objective of this study was to analyze whether a disproportionate number of cases of ICS are reported for cariprazine or brexpiprazole in EudraVigilance. A case/non-case study was conducted to assess the association between ICS and these antipsychotics, calculating reporting odds ratios (RORs) from their respective approval date to Nov 17, 2020. First, cases involving cariprazine or brexpiprazole were compared with those involving all other drugs. Second, to reduce the risk of confounding by indication, the RORs for cariprazine and brexpiprazole were compared with other antipsychotics. Besides, to evaluate a possible notoriety bias, a sensitivity analysis excluding aripiprazole was performed. Seven cases of ICS were reported for cariprazine and another seven for brexpiprazole. The ROR for cariprazine was 28.3 (95% confidence interval [CI], 13.4-59.8) and 33.4 (15.8-70.1) in the case of brexpiprazole. Nonetheless, this association disappeared for cariprazine when compared with other antipsychotics drugs. However, when excluding aripiprazole from the analysis, a safety signal emerged. Although our study is the first to suggest an association between cariprazine, brexpiprazole and ICS, these results should only be considered as exploratory in the context of safety signal detection. Further, well designed observational analytical studies will be needed to confirm these results.

Effectiveness of Electroconvulsive Therapy in Patients With Advanced Parkinson Disease

OBJECTIVES

In addition to motor symptoms, patients with Parkinson disease (PD) experience various psychiatric comorbidities, including impulse control disorders (ICDs). Moreover, antiparkinsonian drugs sometimes cause psychiatric symptoms. Antiparkinsonian and antipsychotic drugs are competitive in pharmacodynamics, and psychotropic drugs, including antidepressants, may worsen motor symptoms or induce adverse reactions. Considering this conflicting situation, we examined the effectiveness of electroconvulsive therapy (ECT) on both motor and psychiatric symptoms in PD.

METHODS

We retrospectively examined 12 PD patients with advanced motor symptoms and drug-resistant psychiatric symptoms, including ICDs, who had undergone ECT. Both before and after ECT, the severity of PD motor symptoms were evaluated using Hoehn and Yahr staging, while psychiatric symptoms were evaluated using the Neuropsychiatric Inventory. The patients' doses of antiparkinsonian and antipsychotic drugs were also assessed before and after ECT.

RESULTS

Both the mean Hoehn and Yahr and Neuropsychiatric Inventory scores were significantly decreased after ECT. The symptoms of ICDs, which were observed in 5 patients, disappeared following ECT. Improvements in motor symptoms and psychiatric symptoms lasted for more than 1 year in 5 cases and 9 cases, respectively. Furthermore, the daily dose of antiparkinsonian drugs was significantly decreased in 6 cases.

CONCLUSIONS

Our results demonstrated that ECT was effective for both severe motor symptoms and psychiatric symptoms in advanced PD patients. ECT might be a solution for the conflicting problem of treating both motor and psychiatric symptoms in PD.

Increased risk for developing gambling disorder under the treatment with pramipexole, ropinirole, and aripiprazole: A nationwide register study in Sweden

Gambling Disorder (GD) has recently been reclassified from an impulse-control disorder to a behavioural addiction and, as in other addictive disorders, the dopaminergic reward system is involved. According to neuroimaging studies, alterations within the striatal dopaminergic signalling can occur in GD. However, the findings to date are controversial and there has been no agreement yet on how the reward system is affected on a molecular basis. Within the last 20 years, there has been growing evidence for a higher risk to develop GD in response to certain dopaminergic medication. Especially the dopamine agonists pramipexole and ropinirole, and the dopamine modulator aripiprazole seem to increase the likelihood for GD. The goal of this study was to examine the association between a prescription for either of the three pharmaceuticals and a GD diagnosis in a large cross-sectional study of the Swedish population. Compared to patients with any other dopaminergic drug prescription (38.7% with GD), the diagnosis was more common in patients with a dopamine agonist prescription (69.8% with GD), resulting in an odds ratio of 3.2. A similar association was found between aripiprazole prescriptions and GD diagnoses, which were analysed within the subgroup of all patients with schizophrenia or a schizotypal, delusional, or another non-mood psychotic disorder. An aripiprazole prescription increased the likelihood of GD (88.8%) in comparison to patients without an aripiprazole prescription (71.2%) with an odds ratio of 3.4. This study contributes to the increasingly reliable evidence for an association between several dopaminergic drugs and a higher risk for developing GD. Therefore, one future research goal should be a better understanding of the neurobiology in GD to be able to design more selective dopaminergic medication with less severe side effects. Additionally, this knowledge could enable the development of pharmacotherapy in GD and other addictive disorders.

[Separation and identification of impurities from intermediates of istradefylline]

Istradefylline is a novel selective adenosine A2A receptor antagonist that is used to treat Parkinson's disease and improve motor dysfunction in the early stage of this disease. During the synthesis of intermediate A1 (6-amino-1,3-diethyl-2,4-(1H,3H)-pyrimidinedione), at least two by-products were formed under alkaline or high-temperature conditions. In a previous study, one of the by-products in the synthesis of the intermediate was studied, and its structure was identified as (E)-N-ethyl-2-cyano-3-ethylamino-2-butene amide. In this study, we used high performance liquid chromatography (HPLC) to analyze another impurity formed during the synthesis of A1, and the following steps were executed: 0.4 g of intermediate was weighed and added to a 50 mL beaker, followed by the sequential addition of 8 mL water and 8 mL acetonitrile, and then, ultrasonic dissolution was performed. Finally, the solution was filtered through a 0.45-μm organic membrane and the test sample solution was obtained. We used the Agilent zorbax C18 chromatography column, with acetonitrile (A)/water(B) as the mobile phase under gradient elution ((tmin/A∶B)=t0/20∶80, t15/60∶40, t20-t50/90∶10). The detector wavelength is 268 nm. In order to separate the impurity from A1, we used a Ceres B preparative column, with acetonitrile-water (30/70, v/v) as the mobile phase. The flow rate was set at 30 mL/min, and the detection wavelength was 268 nm. The structure of the impurity was confirmed by high-resolution mass spectrometry (HRMS), one-dimensional nuclear magnetic resonance (NMR), and two-dimensional nuclear magnetic resonance (2D NMR), and characterized by single-crystal X-ray diffraction (XRD). In MS experiments, an electrospray ionization (ESI) source was used with positive ion scanning. In the NMR experiments, we used tetramethylsilane (TMS) as the internal standard and deuterated dimethyl sulfoxide (DMSO-d6) as the solvent to obtain the spectra. The results of preparative high performance liquid chromatography (Prep-HPLC) showed that good separation effect could be achieved by isocratic elution, and the impurity was perfectly separated. The1H-NMR spectral data are as follows:1H-NMR (600 MHz, DMSO): δ 1.01 (q, J=6.9 Hz, 3H), 1.02 (q, J=6.9 Hz, 3H), 1.07 (t, J=6.9 Hz, 3H), 3.04 (p, J=6.8 Hz, 2H), 3.74 (q, J=7.0 Hz, 2H), 3.94 (q, J=7.1 Hz, 2H), 5.85 (s, 1H). The 13C-NMR spectral data are summarized as follows: 13C-NMR (150 MHz, DMSO): δ13.9, 14.1, 15.9, 34.6, 34.9, 36.9, 81.9, 152.2, 153.3, 159.3, 162.0. The impurity was characterized by single-crystal XRD, and its spatial structure was further verified and determined as 1-(1,3-diethyl-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-yl)-3-ethylurea. Based on the chemical structure of the impurity, we propose the following mechanism for the impurity: when A1 is synthesized under alkaline conditions or at high temperature, excessive diethylurea continues to undergo amidation with A1 to obtain this by-product. Although the formation mechanism of the impurity studied in this paper is different from that of the intermediate A1 impurity (E)-N-ethyl-2-cyano-3-ethylamino-2-butene amide, both the impurities are formed at high temperatures. Both will be accompanied by A1 in the subsequent reaction of istradefylline synthesis. The relationship between drug impurities and drug safety is a complex relationship that is affected by many factors. Generally, most impurities in drugs have potential biological activities, and some even interact with the drugs, thus affecting their efficacy and safety and inducing toxic effects. Therefore, to ensure the quality of istradefylline, it is necessary to control the impurity content during the production. The findings of this paper may provide guidelines for controlling the impurity content in istradefylline.

Pharmacological and Genetic Evidence of Dopamine Receptor 3-Mediated Vasoconstriction in Isolated Mouse Aorta

Dopamine receptors (DRs) are generally considered as mediators of vasomotor functions. However, when used in pharmacological studies, dopamine and/or DR agonists may not discriminate among different DR subtypes and may even stimulate alpha1 and beta-adrenoceptors. Here, we tested the hypothesis that D2R and/or D3R may specifically induce vasoconstriction in isolated mouse aorta. Aorta, isolated from wild-type (WT) and D3R-/- mice, was mounted in a wire myograph and challenged with cumulative concentrations of phenylephrine (PE), acetylcholine (ACh), and the D3R agonist 7-hydrxy-N,N-dipropyl-2-aminotetralin (7-OH-DPAT), with or without the D2R antagonist L741,626 and the D3R antagonist SB-277011-A. The vasoconstriction to PE and the vasodilatation to ACh were not different in WT and D3R-/-; in contrast, the contractile responses to 7-OH-DPAT were significantly weaker in D3R-/-, though not abolished. L741,626 did not change the contractile response induced by 7-OH-DPAT in WT or in D3R-/-, whereas SB-277011-A significantly reduced it in WT but did not in D3R-/-. D3R mRNA (assessed by qPCR) was about 5-fold more abundant than D2R mRNA in aorta from WT and undetectable in aorta from D3R-/-. Following transduction with lentivirus (72-h incubation) delivering synthetic microRNAs to specifically inactivate D2R (LV-miR-D2) or D3R (LV-miR-D3), the contractile response to 7-OH-DPAT was unaffected by LV-miR-D2, while it was significantly reduced by LV-miR-D3. These data indicate that, at least in mouse aorta, D3R stimulation induces vasoconstriction, while D2R stimulation does not. This is consistent with the higher expression level of D3R. The residual vasoconstriction elicited by high concentration D3R agonist in D3R-/- and/or in the presence of D3R antagonist is likely to be unrelated to DRs.

Cybersex addiction in a gay man: a case report

BACKGROUND

Cybersex addiction is a sexual addiction characterized by virtual Internet sexual activity that causes serious negative consequences to one's physical, mental, social, and/or financial well-being. Previous studies have mostly addressed cybersex addiction in heterosexual males.

PURPOSE

To describe a case report of a 26-year-old gay man suffering from a cybersex addiction.

METHODS

We use Griffiths' model of the common components of addictions.

RESULTS

We reveal this case report of cybersex addiction possesses all of six components universal for addictions.

CONCLUSIONS

In light of the increasing prevalence of various behavioral addictions (especially, Internet addictions), clinical psychiatrists should be aware of the cybersex addiction phenomenon.

Multimodal investigation of dopamine D2/D3 receptors, default mode network suppression, and cognitive control in cocaine-use disorder

Stimulant-use disorders have been associated with lower availability of dopamine type-2 receptors (D2R) and greater availability of type-3 receptors (D3R). Links between D2R levels, cognitive performance, and suppression of the default mode network (DMN) during executive functioning have been observed in healthy and addicted populations; however, there is limited evidence regarding a potential role of elevated D3R in influencing cognitive control processes in groups with and without addictions. Sixteen individuals with cocaine-use disorder (CUD) and 16 healthy comparison (HC) participants completed [¹¹C]-(+)-PHNO PET imaging of D2R and D3R availability and fMRI during a Stroop task of cognitive control. Independent component analysis was performed on fMRI data to assess DMN suppression during Stroop performance. In HC individuals, lower D2R-related binding in the dorsal putamen was associated with improved task performance and greater DMN suppression. By comparison, in individuals with CUD, greater D3R-related binding in the substantia nigra was associated with improved performance and greater DMN suppression. Exploratory moderated-mediation analyses indicated that DMN suppression was associated with Stroop performance indirectly through D2R in HC and D3R in CUD participants, and these indirect effects were different between groups. To our knowledge, this is the first evidence of a dissociative and potentially beneficial role of elevated D3R availability in executive functioning in cocaine-use disorder.

Impulse Control Disorders in Parkinson's Disease: Epidemiology, Pathogenesis and Therapeutic Strategies

Impulse control disorders (ICDs) in Parkinson's disease (PD) are aberrant behavior such as pathological gambling, hypersexuality, binge eating, and compulsive buying, which typically occur as a result of dopaminergic therapy. Numerous studies have focused on the broad spectrum of ICDs-related behaviors and their tremendous impact on patients and their family members. Recent advances have improved our understanding of ICDs. In this review, we discuss the epidemiology, pathogenesis and treatment of ICDs in the setting of PD.

The risks of medical treatment of prolactinoma

First-line treatment of prolactinoma is usually medical, based on dopamine agonists receptors, mainly cabergoline. The classical side-effects of cabergoline (low blood pressure and nausea) have been well known since it was first introduced. Other side-effects, however, are more controversial or simply less frequent, but need to be considered during monitoring. This review will focus on these side-effects: cardiac valvular fibrosis, pleural, pericardial and retroperitoneal fibrosis, addictive/compulsive behaviors, and risks secondary to significantly decreased tumor volume. We will also describe how such side-effects should be monitored and managed. In our opinion, the low prevalence of these side-effects should not cast doubt on the role of cabergoline in the therapeutic algorithm of prolactinoma.

Problem Gambling Associated With Aripiprazole in First-Episode Psychosis Patients: A Series of 6 Case Reports

BACKGROUND

Aripiprazole (ARI), an antipsychotic drug used to treat various mental health disorders, has recently been associated with the emergence of problem gambling (PBG). However, few cases have been reported in the schizophrenia-related psychotic disorders population, and even fewer provided sufficient details to systematically assess the causality of the association.

METHODS

This article describes 6 cases with first-episode psychosis in whom PBG emerged while on ARI. Detailed information was gathered from clinical staff and patients' families to systematically assess the causal link between ARI and the emergence of PBG using the Naranjo and Liverpool Adverse Drug Reaction scales.

FINDINGS

Five of these cases were previously diagnosed with a substance use disorder and/or cluster B personality traits. Five had received a more potent dopaminergic antagonist treatment before being switched to ARI. Two of them had presented PBG before being diagnosed with a psychotic disorder. The level of certainty about the causal role of ARI varied from possible to certain, and in 4 cases, the 2 scales yielded different ratings.

IMPLICATIONS

Although these cases suggest that ARI may be associated with the emergence of PBG in the early course of schizophrenia-related psychotic disorders, they cannot prove the causality or the strength of this association. They provide the impetus to perform adequately powered and well-controlled prospective studies to draw more definite conclusion about the causality of this association and, in the meantime, further emphasize the need to carefully assess PBG in this population.

Contributing Factors and Evolution of Impulse Control Disorder in the Luxembourg Parkinson Cohort

Background: To establish the frequency of impulse control disorder (ICD) in Parkinson's disease (PD).

Methods: Within the Luxembourg Parkinson's Study, PD patients were evaluated for ICD presence (score ≥ 1 on MDS-UPDRS I item 1.6), use of dopamine agonists (DA) and other medications.

Results: 470 patients were enrolled. Among 217 patients without DA use, 6.9% scored positive for ICD, vs. 15.4% among 253 patients with DA use (p = 0.005). The regression analysis showed that age at PD diagnosis had only a minor impact on ICD occurrence, while there was no influence by gender or co-medications. The longitudinal study over 2 years in 156 patients demonstrated increasing ICD frequency in DA users (p = 0.005).

Conclusion: This large and non-interventional study confirms that PD patients with DA treatment show higher frequency of ICD than patients without DA use. It newly demonstrates that ICD can develop independently from age, gender, or co-medications.

Should compulsive sexual behavior (CSB) be considered as a behavioral addiction? A debate paper presenting the opposing view

BACKGROUND AND AIMS

Compulsive sexual behavior disorder (CSBD) has been a long debated issue. While formerly the discussion was about whether to regard CSBD as a distinctive disorder, the current debate is dealing with the classification of this phenomenon. One of the prominent voices in this field considers CSBD as a behavioral addiction and proposes CSBD to be called and diagnosed as sexual addiction (SA). This present debate paper will review the existing evidence supporting this view and it will argue against it.

RESULTS

We have found that a great deal of the current literature is anecdotal while empirical evidence is insufficient. First, the reports about the prevalence of CSBD are contradictory. Additionally, the field mainly suffers from inconsistent defining criteria of CSBD and a consensus which symptoms should be included. As a result, the empirical evidence that does exist is mostly about some symptoms individually and not on the disorder as a whole construct.

CONCLUSIONS

We conclude that currently, there is not enough data supporting CSBD as a behavioral addiction. Further research has to be done, examining CSBD phenomenology as a whole construct and based on a homogeneous criterion.

Association Between Pathophysiological Mechanisms of Diabetic Retinopathy and Parkinson's Disease

Diabetic retinopathy, the most common complication of diabetes, is a neurodegenerative disease in the eye. And Parkinson's disease, affecting the health of 1-2% of people over 60 years old throughout the world, is the second largest neurodegenerative disease in the brain. As the understanding of diabetic retinopathy and Parkinson's disease deepens, the two diseases are found to show correlation in incidence, similarity in clinical presentation, and close association in pathophysiological mechanisms. To reveal the association between pathophysiological mechanisms of the two disease, in this review, the shared pathophysiological factors of diabetic retinopathy and Parkinson's disease are summarized and classified into dopaminergic system, circadian rhythm, neurotrophic factors, α-synuclein, and Wnt signaling pathways. Furthermore, similar and different mechanisms so far as the shared pathophysiological factors of the two disorders are discussed systematically. Finally, a brief summary and new perspectives are presented to provide new directions for further efforts on the association, exploration, and clinical prevention and treatment of diabetic retinopathy and Parkinson's disease.

Drugs-Induced Pathological Gambling: An Analysis of Italian Spontaneous Reporting System

Pathological gambling has been reported as a direct complication of Parkinson’s disease and its pharmacological treatment based on dopamine agonists. Moreover, further medications (not dopamine agonists) were associated to the occurrence of gambling disorder. We aim to analyze the spontaneous reports of gambling disorder on the whole Italian territory with a focus on Campania Region (Southern Italy) from January 1st 2002 to July 31st 2018. We analyzed gambling disorder’s reports across the 2002–2018 period in the Italian spontaneous reporting database (Rete Nazionale di Farmacovigilanza—RNF), with a focus on Campania region. 94 suspected cases of gambling disorder associated to apomorphine, aripiprazole, cabergoline, levodopa, levodopa and derivatives in association with entacapone/benserazide and carbidopa, pergolide, pramipexole, ropinirole, and rotigotine were reported into the RNF. Of these cases, two related to pramipexole and one to aripiprazole were sent to Campania Pharmacovigilance Regional Centre. Although it is widely recognized that dopamine agonists may induce behavioral disorders, Parkinson’s disease is itself associated to pathological gambling, compulsive shopping and eating. Since our results could not clarify the correlation between Parkinson’s disease, its pharmacological treatment and pathological gambling, in order to better define this correlation there is a need to conduct further ad hoc observational studies.

Ropinirole, a dopamine agonist with high D3 affinity, reduces proactive inhibition: A double-blind, placebo-controlled study in healthy adults

Response inhibition describes the cognitive processes mediating the suppression of unwanted actions. A network involving the basal ganglia mediates two forms of response inhibition: reactive and proactive inhibition. Reactive inhibition serves to abruptly stop motor activity, whereas proactive inhibition is goal-orientated and results in slowing of motor activity in anticipation of stopping. Due to its impairment in several psychiatric disorders, the neurochemistry of response inhibition has become of recent interest. Dopamine has been posed as a candidate mediator of response inhibition due to its role in functioning of the basal ganglia and the observation that patients with Parkinson's disease on dopamine agonists develop impulse control disorders. Although the effects of dopamine on reactive inhibition have been studied, substantial literature on the role of dopamine on proactive inhibition is lacking. To fill this gap, we devised a double-blind, placebo-controlled study of 1 mg ropinirole (a dopamine agonist) on response inhibition in healthy volunteers. We found that whilst reactive inhibition was unchanged, proactive inhibition was impaired when participants were on ropinirole relative to when on placebo. To investigate how ropinirole mediated this effect on proactive inhibition, we used hierarchical drift-diffusion modelling. We found that ropinirole impaired the ability to raise the decision threshold when proactive inhibition was called upon. Our results provide novel evidence that an acute dose of ropinirole selectively reduces proactive inhibition in healthy participants. These results may help explain how ropinirole induces impulse control disorders in susceptible patients with Parkinson's disease.

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Proactive but not reactive inhibition is impaired under the influence of ropinirole vs placebo.

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Ropinirole impairs the ability to raise the decision threshold when proactive inhibition is called upon.

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We provide novel evidence that an acute dose of ropinirole selectively reduces proactive inhibition in healthy participants.

Changes in sexual behavior patterns due to stimulants use: three case reports

The paper describes three case reports of changes in sexual behavior patterns in male patients who use stimulants (amphetamine and mephedrone). Two of them demonstrate that the consumption of stimulants may lead to hypersexuality and excessive masturbation. Case report three shows that mephedrone use results in such typical stimulant-related subjective effects as the intensification of sensory experiences and sexual arousal. It leads to the loss of interest in sex without mephedrone. In light of the popularity of sex under the influence of drugs, clinicians should be aware of this phenomenon, since it is associated with high-risk sexual behavior. The description of clinical cases on the link between sex and drugs expands our knowledge in this area, leading to more effective treatment interventions.

Lower nucleus accumbens α-synuclein load and D3 receptor levels in Parkinson's disease with impulsive compulsive behaviours

Impulsive compulsive behaviours in Parkinson's disease have been linked to increased dopaminergic release in the ventral striatum and excessive stimulation of dopamine D3 receptors. Thirty-one patients with impulsive compulsive behaviours and Parkinson's disease who donated their brains to the Queen Square Brain Bank for Neurological Disorders were assessed for α-synuclein neuropathological load and tyrosine hydroxylase levels in the nucleus accumbens, dorsal putamen and caudate using immunohistochemistry. Dopamine D2 and dopamine D3 receptors protein levels in the nucleus accumbens, frontal cortex and putamen were determined using western blotting. Results were compared to 29 Parkinson's disease cases without impulsive compulsive behaviours matched by age, sex, disease duration, age at Parkinson's disease onset and disease duration. The majority of patients with impulsive compulsive behaviours had dopamine dysregulation syndrome. Patients with Parkinson's disease and impulsive compulsive behaviours had lower α-synuclein load and dopamine D3 receptor levels in the nucleus accumbens. No differences were seen between groups in the other brain areas and in the analysis of tyrosine hydroxylase and dopamine D2 receptor levels. Lower α-synuclein load in the nucleus accumbens of individuals with Parkinson's disease and impulsive compulsive behaviours was confirmed on western blotting. Downregulation of the dopamine D3 receptor levels may have occurred either as a consequence of the degenerative process or of a pre-morbid trait. The lower levels of α-synuclein may have contributed to an excessive stimulation of the ventral striatum resulting in impulsive compulsive behaviours.

The adverse effects of pramipexole on probability discounting are not reversed by acute D2 or D3 receptor antagonism

Pramipexole (PPX) is a D₂ and D₃ dopamine receptor agonist approved for clinical use, which is associated with a higher risk of impulse-control disorders. Using a rat model, we recently found that low doses of the monoamine-depleting agent reserpine (RES; 1 mg/kg/day, SC) dramatically increased the untoward effects of PPX (0.3 mg/kg/day, SC) on probability discounting, a key impulsivity function. To further understand the neurobehavioral mechanisms underlying these effects, we first tested whether the combination of PPX and RES may lead to a generalized enhancement in risk taking, as tested in the suspended wire-beam paradigm. The association of RES and PPX did not augment the proclivity of rats to cross the bridge in order to obtain a reward, suggesting that the effects of RES and PPX on probability discounting do not reflect a generalized increase in impulsivity. We then studied what receptors mediate the effects of PPX in RES-treated rats. The combination of RES and PPX increased membrane expression and binding of D₃, but not D₂ dopamine receptors, in the nucleus accumbens. However, the behavioral effects of PPX and RES were not reduced by acute treatments with the D₂/D₃ receptor antagonist raclopride (0.01-0.05 mg/kg, SC), the highly selective D₂ receptor antagonist L-741,626 (0.1-1 mg/kg, SC) or the D₃ receptor antagonists GR 103691 (0.1-0.3 mg/kg, SC) and SB 277011A (1-10 mg/kg, SC). These findings collectively suggest that the effects of PPX in probability discounting do not reflect generalized enhancements in impulsivity or acute dopamine D₂ or D₃ receptor activation.