Pathological gambling associated with dopamine agonist therapy in Parkinson's disease

Dopamine agonist serum concentrations and impulse control disorders in Parkinson's disease

BACKGROUND AND PURPOSE

Impulse control disorders (ICDs) are common among Parkinson's disease patients using dopamine agonists. We wanted to determine whether ICD patients have higher dopamine agonist serum concentrations than those without any sign of ICD.

METHODS

Patients who used either pramipexole or ropinirole depot once daily were screened for ICDs using the validated Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease-Rating Scale. Those who scored above the cut-off for one or more of the four defined ICDs (gambling, compulsive sexual behavior, compulsive shopping, and binge-eating) were compared in a case-control study to patients who scored zero points (no evidence of ICD) on the same items. They were examined clinically and evaluated using relevant scales. Three blood samples were taken on the same day: before daily dose, and then 6 and 12 h later.

RESULTS

Forty-six patients were included: 19 ICD-positive and 27 controls. Ropinirole serum concentrations 6 h after daily intake (Cmax ) were higher in the case group compared to the control group, as was the daily ropinirole dosage. No differences were observed in serum concentrations, dosage or total drug exposure for pramipexole. Disease duration and length of dopamine agonist treatment was significantly longer among ICD patients for ropinirole, but not for pramipexole.

CONCLUSIONS

The use of pramipexole may in itself confer high ICD risk, whereas ICDs among ropinirole users depend more on serum concentration and drug exposure. The pharmacokinetic properties of ropinirole make it challenging to predict its effects on patients, which supports the need for therapeutic drug monitoring to reduce risk of ICD.

Cerebellar impulsivity-compulsivity assessment scale

OBJECTIVE

The cerebellum has been identified as the key brain region that modulates reward processing in animal models. Consistently, we recently found that people with cerebellar ataxia have impulsive and compulsive behaviors (ICBs), the main symptoms related to abnormal reward processing. Due to the lack of a validated scale to quantitatively measure ICBs in cerebellar disorders, we aim to develop and validate a new scale, Cerebellar Impulsivity-Compulsivity Assessment (CIA).

METHODS

We recruited 62 cerebellar ataxia cases, categorized into those with ICBs and those without. We developed a preliminary version of CIA, containing 17 questions. We studied the internal consistency, test-retest reliability, and inter-rater reliability to formulate the final version of CIA, which constitutes only 10 questions. The receiver operating characteristic curve (ROC) was generated to assess the sensitivity and specificity of CIA.

RESULTS

Cerebellar ataxia cases with ICBs have threefold higher total preliminary CIA scores than those without ICBs (12.06 ± 5.96 vs. 4.68 ± 3.50, p = 0.038). Cronbach's alpha revealed good internal consistency across all items (α > 0.70). By performing the test-retest reliability and inter-rater reliability on the preliminary version of CIA, we excluded seven questions (r < 0.70) and generated the final version of CIA. Based on the ROC, a score of 8.0 in CIA was chosen as the cut-off for ICBs in individuals with cerebellar ataxia with 81% sensitivity and 81% specificity.

INTERPRETATION

CIA is a novel tool to assess ICBs in cerebellar ataxia and broaden our understanding of the cerebellum-related cognitive and behavioral symptoms.

Role of dopamine and clinical heterogeneity in cognitive dysfunction in Parkinson's disease

Parkinson's disease (PD) is commonly treated with dopaminergic medication, which enhances some, while impairing other cognitive functions. It can even contribute to impulse control disorder and addiction. We describe the history of research supporting the dopamine overdose hypothesis, which accounts for the large within-patient variability in dopaminergic medication effects across different tasks by referring to the spatially non-uniform pattern of dopamine depletion in dorsal versus ventral striatum. However, there is tremendous variability in dopaminergic medication effects not just within patients across distinct tasks, but also across different patients. In the second part of this chapter we review recent studies addressing the large individual variability in the negative side effects of dopaminergic medication on functions that implicate dopamine, such as value-based learning and choice. These studies begin to unravel the mechanisms of dopamine overdosing, thus revising the strict version of the overdose hypothesis. For example, the work shows that the canonical boosting of reward-versus punishment-based choice by medication is greater in patients with depression and a non-tremor phenotype, which both implicate, among other pathology, more rather than less severe dysregulation of the mesolimbic dopamine system. Future longitudinal cohort studies are needed to identify how to optimally combine different clinical, personality, cognitive, neural, genetic and molecular predictors of detrimental medication effects in order to account for as much of the relevant variability as possible. This will provide a useful tool for precision neurology, allowing individual and contextual tailoring of (the dose of) dopaminergic medication in order to maximize its cognitive benefits, yet minimize its side effects.

Impulse control disorders, dopamine dysregulation syndrome and sex dysfunction in Parkinson's disease

Hypersexuality (HS), characterized by an aberrant, compulsive and inappropriate sexual drive, is an underreported and undermanaged complication of the treatment with dopamine agonists in patients with Parkinson's disease (PD). HS is part of the spectrum of impulse control disorders (ICDs). The failure to control these addictive behaviors is distressing for the patient and it is associated with important consequences. Reports of the prevalence of HS showed different results, due to the lack of standardized diagnostic criteria, but also due to the embarrassment or guilt feelings that patients experience regarding their sexual behaviors. Overall, it is considered that HS may occur in 1.92-22.8% of PD patients and the main risk factors involved could be male sex and genetic susceptibility. The pathophysiology of HS is unknown, but several degenerative mechanisms were proposed, involving dopaminergic, serotoninergic and noradrenergic pathways in cerebral regions responsive for planning and rewarding. There are no standardized tools for the assessment of HS in PD patients; however, several scales and questionnaires were developed with the aim of screening and rating the severity of ICDs, including HS. The management of HS is challenging. Discontinuation or reducing the dopaminergic treatment was effective in some cases, but it might lead to worsening of the motor function. A multidisciplinary approach is mandatory to manage the other associated aspects, such as psychological and social consequences of HS.

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.

Seeking motivation and reward: roles of dopamine, hippocampus and supramammillo-septal pathway

Reinforcement learning and goal-seeking behavior are thought to be mediated by midbrain dopamine neurons. However, little is known about neural substrates of curiosity and exploratory behavior, which occur in the absence of clear goal or reward. This is despite behavioral scientists having long suggested that curiosity and exploratory behaviors are regulated by an innate drive. We refer to such behavior as information-seeking behavior and propose 1) key neural substrates and 2) the concept of environment prediction error as a framework to understand information-seeking processes. The cognitive aspect of information-seeking behavior, including the perception of salience and uncertainty, involves, in part, the pathways from the posterior hypothalamic supramammillary region to the hippocampal formation. The vigor of such behavior is modulated by the following: supramammillary glutamatergic neurons; their projections to medial septal glutamatergic neurons; and the projections of medial septal glutamatergic neurons to ventral tegmental dopaminergic neurons. Phasic responses of dopaminergic neurons are characterized as signaling potentially important stimuli rather than rewards. This paper describes how novel stimuli and uncertainty trigger seeking motivation and how these neural substrates modulate information-seeking behavior.

Decision making in Parkinson's disease: An analysis of the studies using the Iowa Gambling Task

In Parkinson's disease (PD) impairments in decision making can occur, in particular because of the tendency toward risky and rewarding options. The Iowa Gambling Task has been widely used to investigate decision processes involving these options. The task assesses the ability to manage risk and to learn from feedback. The present paper aims at critically examining those studies in which this task has been administered to PD patients, in order to understand possible anomalies in patients' decision processes and which variables are responsible for that. A meta‐analysis has been conducted as well. Features of the task, sociodemographic and clinical aspects (including daily drugs intake), cognitive conditions and emotional disorders of the patients have been taken into account. Neural correlates of decision‐making competences were considered. It emerged that PD patients show a trend of preference toward risky choices, probably due to an impairment in anticipating the unrewarding consequences or to an insensitiveness to punishment. The possible role played by dopamine medications in decision making under uncertain conditions, affecting basal ganglia and structures involved in the limbic loop, was discussed. Attention has been focused on some aspects that need to be investigated in further research, in order to delve into this issue and promote patients' quality of life.

Objective assessment of impulse control disorder in patients with Parkinson's disease using a low-cost LEGO-like EEG headset: a feasibility study

Background

Patients with Parkinson’s disease (PD) can develop impulse control disorders (ICDs) while undergoing a pharmacological treatment for motor control dysfunctions with a dopamine agonist (DA). Conventional clinical interviews or questionnaires can be biased and may not accurately diagnose at the early stage. A wearable electroencephalogram (EEG)-sensing headset paired with an examination procedure can be a potential user-friendly method to explore ICD-related signatures that can detect its early signs and progression by reflecting brain activity.

Methods

A stereotypical Go/NoGo test that targets impulse inhibition was performed on 59 individuals, including healthy controls, patients with PD, and patients with PD diagnosed by ICDs. We conducted two Go/NoGo sessions before and after the DA-pharmacological treatment for the PD and ICD groups. A low-cost LEGO-like EEG headset was used to record concurrent EEG signals. Then, we used the event-related potential (ERP) analytical framework to explore ICD-related EEG abnormalities after DA treatment.

Results

After the DA treatment, only the ICD-diagnosed PD patients made more behavioral errors and tended to exhibit the deterioration for the NoGo N2 and P3 peak amplitudes at fronto-central electrodes in contrast to the HC and PD groups. Particularly, the extent of the diminished NoGo-N2 amplitude was prone to be modulated by the ICD scores at Fz with marginal statistical significance (r = − 0.34, p = 0.07).

Conclusions

The low-cost LEGO-like EEG headset successfully captured ERP waveforms and objectively assessed ICD in patients with PD undergoing DA treatment. This objective neuro-evidence could provide complementary information to conventional clinical scales used to diagnose ICD adverse effects.

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.

Attenuated Directed Exploration during Reinforcement Learning in Gambling Disorder

Gambling disorder (GD) is a behavioral addiction associated with impairments in value-based decision-making and behavioral flexibility and might be linked to changes in the dopamine system. Maximizing long-term rewards requires a flexible trade-off between the exploitation of known options and the exploration of novel options for information gain. This exploration-exploitation trade-off is thought to depend on dopamine neurotransmission. We hypothesized that human gamblers would show a reduction in directed (uncertainty-based) exploration, accompanied by changes in brain activity in a fronto-parietal exploration-related network. Twenty-three frequent, non-treatment seeking gamblers and twenty-three healthy matched controls (all male) performed a four-armed bandit task during functional magnetic resonance imaging (fMRI). Computational modeling using hierarchical Bayesian parameter estimation revealed signatures of directed exploration, random exploration, and perseveration in both groups. Gamblers showed a reduction in directed exploration, whereas random exploration and perseveration were similar between groups. Neuroimaging revealed no evidence for group differences in neural representations of basic task variables (expected value, prediction errors). Our hypothesis of reduced frontal pole (FP) recruitment in gamblers was not supported. Exploratory analyses showed that during directed exploration, gamblers showed reduced parietal cortex and substantia-nigra/ventral-tegmental-area activity. Cross-validated classification analyses revealed that connectivity in an exploration-related network was predictive of group status, suggesting that connectivity patterns might be more predictive of problem gambling than univariate effects. Findings reveal specific reductions of strategic exploration in gamblers that might be linked to altered processing in a fronto-parietal network and/or changes in dopamine neurotransmission implicated in GD.SIGNIFICANCE STATEMENT Wiehler et al. (2021) report that gamblers rely less on the strategic exploration of unknown, but potentially better rewards during reward learning. This is reflected in a related network of brain activity. Parameters of this network can be used to predict the presence of problem gambling behavior in participants.

Management of psychiatric disorders in Parkinson's disease : Neurotherapeutics - Movement Disorders Therapeutics

Affective disorders (depression and anxiety), psychosis, impulse control disorders, and apathy are common and sometimes disabling psychiatric conditions in Parkinson disease (PD). Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their high frequency, there remains incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically co- or multimorbid, and there is great intra- and interindividual variability in presentation [1]. The neuropathophysiological changes that occur in PD, as well as the association between PD treatment and particular psychiatric disorders, suggest a neurobiological contribution to many psychiatric symptoms. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated, and although psychotropic medication use is common, randomized controlled trials demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors, and most importantly, establishing efficacious and well-tolerated treatment strategies.

Gender Differences in Impulse Control Disorders and Related Behaviors in Patients with Parkinson's Disease and its Impact on Quality of Life

BACKGROUND

Dopaminergic medications administered to remedy motor symptoms in Parkinson's disease are associated with an enhanced risk for impulse control disorders (ICD) and related compulsive behaviors (ICD-RB). Thus, the present study focuses on investigating the gender difference in the prevalence of ICD-RBs in Indian PD patients on dopamine replacement therapy (DRT), its impact on quality of life and to identify ICDs relevant in Indian scenario apart from the criteria set in QUIP-RS.

METHOD

This was a hospital-based observational cross-sectional study in which Parkinson's disease patients attending neurology clinic were included. Complete details of anti-parkinsonian therapy along with demographic and clinical variables were recorded on a predesigned Performa. Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease (QUIP), which is a validated quick screening tool, was used to detect ICD-RBs. The relative frequency and comparative impact of ICD on health-related quality of life (QOL) was studied using validated PDQ-39 Questionnaire.

RESULTS

Out of 102 patients, at least one ICD or ICD-RB was present in 41.19% and ≥2 ICD-RBs were present in 15.59%. At least one ICD was present in 16.67%, any ICD-related compulsive behaviors was present in 34.31% patients. The most common was punding and compulsive medication use (12.75% each), followed by hobbyism (7.84%), compulsive eating (6.86%), pathological gambling (3.92%), and hypersexuality, walkabout, and compulsive shopping (2.94% each). ICDs not classified elsewhere such as trichotillomania were found 3 patients (2.94%). ICD-RBs showed a trend to be more frequent in women (44.82% women vs. 39.39% men). As compared with patients without ICD-RBs, those with ICD-RBs were found to have higher dose of LD and DA and higher Hoehn and Yahr stage. ICD-RBs have a negative impact on the quality of life of Parkinson's disease patients.

CONCLUSION

ICDs and ICD-RBs have been included in the behavioral spectrum of nonmotor symptoms in PD. PD patients are at increased risk of developing ICD-RBs which interfere with important activities and have obligation in ordinary life, leading to legal and psychological consequences with a great impact on QOL.

The role of dopamine pharmacotherapy and addiction-like behaviors in Parkinson's disease

Addictions involve a spectrum of behaviors that encompass features of impulsivity and compulsivity, herein referred to as impulsive-compulsive spectrum disorders (ICSDs). The etiology of ICSDs likely involves a complex interplay among neurobiological, psychological and social risk factors. Neurobiological risk factors include the status of the neuroanatomical circuits that govern ICSDs. These circuits can be altered by disease, as well as exogenous influences such as centrally-acting pharmacologics. The 'poster child' for this scenario is Parkinson's disease (PD) medically managed by pharmacological treatments. PD is a progressive neurodegenerative disease that involves a gradual loss of dopaminergic neurons largely within nigrostriatal projections. Replacement therapy includes dopamine receptor agonists that directly activate postsynaptic dopamine receptors (bypassing the requirement for functioning presynaptic terminals). Some clinically useful dopamine agonists, e.g., pramipexole and ropinirole, exhibit high affinity for the D2/D3 receptor subtypes. These agonists provide excellent relief from PD motor symptoms, but some patients exhibit debilitating ICSD. Teasing out the neuropsychiatric contribution of PD-associated pathology from the drugs used to treat PD motor symptoms is challenging. In this review, we posit that modern clinical and preclinical research converge on the conclusion that dopamine replacement therapy can mediate addictions in PD and other neurological disorders. We provide five categories of evidences that align with this position: (i) ICSD prevalence is greater with D2/D3 receptor agonist therapy vs PD alone. (ii) Capacity of dopamine replacement therapy to produce addiction-like behaviors is independent of disease for which the therapy is being provided. (iii) ICSD-like behaviors are recapitulated in laboratory rats with and without PD-like pathology. (iv) Behavioral pathology co-varies with drug exposure. (v) ICSD Features of ICSDs are consistent with agonist pharmacology and neuroanatomical substrates of addictions. Considering the underpinnings of ICSDs in PD should not only help therapeutic decision-making in neurological disorders, but also apprise ICSDs in general.

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.

What drugs modify the risk of iatrogenic impulse-control disorders in Parkinson's disease? A preliminary pharmacoepidemiologic study

INTRODUCTION

Parkinson's disease (PD) patients treated with pramipexole (PPX) and ropinirole (ROP) exhibit a higher risk of developing impulse control disorders (ICDs), including gambling disorder, compulsive shopping, and hypersexuality. The management of ICDs in PD is challenging, due to the limited availability of effective therapeutic alternatives or counteractive strategies. Here, we used a pharmacoepidemiological approach to verify whether the risk for PPX/ROP-associated ICDs in PD patients was reduced by drugs that have been posited to exert therapeutic effects on idiopathic ICDs-including atypical antipsychotics (AAs), selective serotonin reuptake inhibitors (SSRIs), and glutamatergic modulators (GMs).

METHODS

To quantify the strength of the associations between PPX/ROP and other medications with respect to ICD risk, odds ratios (ORs) were calculated by multivariable logistic regression, adjusting for age, gender, marital status race, psychiatric comorbidities, and use of cabergoline and levodopa.

RESULTS

A total of 935 patients were included in the analysis. Use of GMs, SSRIs, and AAs was not associated with a decreased ICD risk in PD patients treated with PPX/ROP; conversely, ICD risk was significantly increased in patients treated with either GMs (Adjusted Odds Ratio, ORa: 14.00 [3.58-54.44]) or SSRIs (ORa: 3.67 [1.07-12.59]). Results were inconclusive for AAs, as available data were insufficient to compute a reliable ORa.

CONCLUSIONS

These results suggest that some of the key pharmacological strategies used to treat idiopathic ICD may not be effective for ICDs associated with PPX and ROP in PD patients. Future studies with larger cohorts are needed to confirm, validate, and extend these findings.

The Neuropsychiatry of Parkinson Disease: A Perfect Storm

Affective disorders, cognitive decline, and psychosis have long been recognized as common in Parkinson disease (PD), and other psychiatric disorders include impulse control disorders, anxiety symptoms, disorders of sleep and wakefulness, and apathy. Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their frequent occurrence, there is incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically multimorbid, and there is great intra- and interindividual variability in presentation. The hallmark neuropathophysiological changes that occur in PD, plus the association between exposure to dopaminergic medications and certain psychiatric disorders, suggest a neurobiological basis for many psychiatric symptoms, although psychological factors are involved as well. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated and although psychotropic medication use is common, controlled studies demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors and establishing efficacious and well-tolerated treatment strategies.

Impulse control disorders in Parkinson's disease: A systematic review on the psychometric properties of the existing measures

Background

A significant percentage of patients suffering from Parkinson’s Disease (PD) experience Impulse Control Disorders (ICDs), contributing to reduced quality of life. As they can be managed by reducing the dopamine dosage, the detection of their presence is crucial for PD treatment plan. Nevertheless, they tend to be under-recognized in clinical practice, since routine screening is not common–despite existing instruments that may support clinicians. This work presents a systematic review on the psychometric properties of instruments measuring ICDs in PD, to test whether clinicians dispose of valid tools that may help them in clinical assessment.

Method

A systematic literature search in three databases (EMBASE, MEDLINE, and PsycINFO) was conducted. Quality of the instruments’ psychometric properties was evaluated with Terwee et al.’s criteria, and methodological quality of the studies was evaluated with the COSMIN Checklist.

Results

Ten studies examining seven instruments were selected. The Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease (QUIP) and the Ardouin Scale of Behavior in Parkinson’s Disease (ASBPD) resulted to be the best from a psychometric point of view.

Conclusions

Though the gold standard for diagnosis remains a detailed diagnostic interview, this review will encourage clinicians to use validated tools to accurately assess ICDs.

Impulse Control Disorders in Parkinson's Disease. A Brief and Comprehensive Review

Impulse control and related disorders (ICDs-RD) encompasses a heterogeneous group of disorders that involve pleasurable behaviors performed repetitively, excessively, and compulsively. The key common symptom in all these disorders is the failure to resist an impulse or temptation to control an act or specific behavior, which is ultimately harmful to oneself or others and interferes in major areas of life. The major symptoms of ICDs include pathological gambling (PG), hypersexualtiy (HS), compulsive buying/shopping (CB) and binge eating (BE) functioning. ICDs and ICDs-RD have been included in the behavioral spectrum of non-motor symptoms in Parkinson's disease (PD) leading, in some cases, to serious financial, legal and psychosocial devastating consequences. Herein we present the prevalence of ICDs, the risk factors, its pathophysiological mechanisms, the link with agonist dopaminergic therapies and therapeutic managements.

Impulse control disorders in Parkinson's disease: A systematic review on risk factors and pathophysiology

AIM

Purpose of this review is to evaluate the potential risk factors that may predispose to the development of Impulse control disorders (ICDs) in Parkinson's Disease (PD) patients, including the effects of dopaminergic therapy.

METHODS

This descriptive review was conducted to identificate risk factors that could cause impulsive control disorders in PD. Studies were found on PubMed (2010-2018), Web Of Science (January 2010-July 2018) and Cochrane (2010-2018) databases.

RESULTS

The data suggest that intrinsic and extrinsic factors may be involved in the development of behavioral complications. To date, the link between PD and the development of ICDs is not very clear, but studies highlight the existence of a predisposition to ICDs in the presence of risk factors.

CONCLUSIONS

A better assessment of the behavioral disorders of PD may be useful in the rehabilitative intervention for increasing the quality of life.

Dopamine Agonists and Impulse Control Disorders: A Complex Association

Impulse control disorders (ICDs) are a well-known adverse effect of dopamine agonists (DAAs). This critical review aims to summarize data on the prevalence and factors associated with the development of an ICD simultaneous to DAA use. A search of two electronic databases was completed from inception to July 2017. The search terms were medical subject headings (MeSH) terms including “dopamine agonists” AND “disruptive disorders”, “impulse control disorders”, or “conduct disorders”. Articles had to fulfill the following criteria to be included: (i) the target problem was an ICD; (ii) the medication was a dopaminergic drug; and (iii) the article was an original article. Of the potential 584 articles, 90 met the criteria for inclusion. DAAs were used in Parkinson’s disease (PD), restless legs syndrome (RLS) or prolactinoma. The prevalence of ICDs ranged from 2.6 to 34.8% in PD patients, reaching higher rates in specific PD populations; a lower prevalence was found in RLS patients. We found only two studies about prolactinoma. The most robust findings relative to the factors associated with the development of an ICD included the type of DAA, the dosage, male gender, a younger age, a history of psychiatric symptoms, an earlier onset of disease, a longer disease duration, and motor complications in PD. This review suggests that DAA use is associated with an increased risk in the occurrence of an ICD, under the combined influence of various factors. Guidelines to help prevent and to treat ICDs when required do exist, although further studies are required to better identify patients with a predisposition.

Dopamine Receptor-Specific Contributions to the Computation of Value

Dopamine is thought to play a crucial role in value-based decision making. However, the specific contributions of different dopamine receptor subtypes to the computation of subjective value remain unknown. Here we demonstrate how the balance between D1 and D2 dopamine receptor subtypes shapes subjective value computation during risky decision making. We administered the D2 receptor antagonist amisulpride or placebo before participants made choices between risky options. Compared with placebo, D2 receptor blockade resulted in more frequent choice of higher risk and higher expected value options. Using a novel model fitting procedure, we concurrently estimated the three parameters that define individual risk attitude according to an influential theoretical account of risky decision making (prospect theory). This analysis revealed that the observed reduction in risk aversion under amisulpride was driven by increased sensitivity to reward magnitude and decreased distortion of outcome probability, resulting in more linear value coding. Our data suggest that different components that govern individual risk attitude are under dopaminergic control, such that D2 receptor blockade facilitates risk taking and expected value processing.

Neuropsychiatric and metabolic aspects of dopaminergic therapy: perspectives from an endocrinologist and a psychiatrist

The dopaminergic treatment represents the primary treatment in prolactinomas, which are the most common pituitary adenomas and account for about 40% of all pituitary tumours with an annual incidence of six to ten cases per million population. The dopaminergic treatment includes ergot and non-ergot derivatives with high affinity for the dopamine receptors D1 or/and D2. Through the activation of the dopaminergic pathway on pituitary lactotrophs, the dopamine agonists inhibit the prolactin synthesis and secretion, therefore normalizing the prolactin levels and restoring eugonadism, but they also lead to tumour shrinkage. Treatment with dopamine agonists has been associated - apart from the common side effects such as gastrointestinal symptoms, dizziness and hypotension - with neuropsychiatric side effects such as impulse control disorders (e.g. pathological gambling, compulsive shopping, hypersexuality and binge eating) and also with behavioral changes from low mood, irritability and verbal aggressiveness up to psychotic and manic symptoms and paranoid delusions not only in patients with prolactinomas but also in patients with Parkinson's disease and restless leg syndrome. They usually have de novo onset after initiation of the dopaminergic treatment and have been mainly reported in patients with Parkinson's disease, who are being treated with higher doses of dopamine agonists. Moreover, dopamine and prolactin seem to play an essential role in the metabolic pathway. Patients with hyperprolactinemia tend to have increased body weight and an altered metabolic profile with hyperinsulinemia and increased prevalence of diabetes mellitus in comparison to healthy individuals and patients with non-functioning pituitary adenomas. Treatment with dopamine agonists in these patients in short-term studies seems to lead to weight loss and amelioration of the metabolic changes. Together these observations provide evidence that dopamine and prolactin have a crucial role both in the regard and metabolic system, findings that merit further investigation in long-term studies.

Effect of Levodopa on Reward and Impulsivity in a Rat Model of Parkinson's Disease

The use of dopamine replacement therapies (DRT) in the treatment of Parkinson’s disease (PD) can lead to the development of dopamine dysregulation syndrome (DDS) and impulse control disorders (ICD), behavioral disturbances characterized by compulsive DRT self-medication and development of impulsive behaviors. However, the mechanisms behind these disturbances are poorly understood. In animal models of PD, the assessment of the rewarding properties of levodopa (LD), one of the most common drugs used in PD, has produced conflicting results, and its ability to promote increased impulsivity is still understudied. Moreover, it is unclear whether acute and chronic LD therapy differently affects reward and impulsivity. In this study we aimed at assessing, in an animal model of PD with bilateral mesostriatal and mesocorticolimbic degeneration, the behavioral effects of LD therapy regarding reward and impulsivity. Animals with either sham or 6-hydroxydopamine (6-OHDA)-induced bilateral lesions in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) were exposed to acute and chronic LD treatment. We used the conditioned place preference (CPP) paradigm to evaluate the rewarding effects of LD, whereas impulsive behavior was measured with the variable delay-to-signal (VDS) task. Correlation analyses between behavioral measurements of reward or impulsivity and lesion extent in SNc/VTA were performed to pinpoint possible anatomical links of LD-induced behavioral changes. We show that LD, particularly when administered chronically, caused the development of impulsive-like behaviors in 6-OHDA-lesioned animals in the VDS. However, neither acute or chronic LD administration had rewarding effects in 6-OHDA-lesioned animals in the CPP. Our results show that in a bilateral rat model of PD, LD leads to the development of impulsive behaviors, strengthening the association between DRT and DDS/ICD in PD.

Impulse Control and Related Disorders in Parkinson's Disease

Impulse control disorders (ICDs), such as compulsive gambling, buying, sexual, and eating behaviors, are a serious and increasingly recognized complication in Parkinson's disease (PD), occurring in up to 20% of PD patients over the course of their illness. Related behaviors include punding (stereotyped, repetitive, purposeless behaviors), dopamine dysregulation syndrome (DDS) (compulsive medication overuse), and hobbyism (e.g., compulsive internet use, artistic endeavors, and writing). These disorders have a significant impact on quality of life and function, strain interpersonal relationships, and worsen caregiver burden, and are associated with significant psychiatric comorbidity. ICDs have been most closely related to the use of dopamine agonists (DAs), while DDS is primarily associated with shorter acting, higher potency dopamine replacement therapy (DRT), such as levodopa. However, in preliminary research ICDs have also been reported to occur with monoamine oxidase inhibitor-B and amantadine treatment, and after deep brain stimulation (DBS) surgery. Other risk factors for ICDs may include sex (e.g., male sex for compulsive sexual behavior, and female sex for compulsive buying behavior); younger age overall at PD onset; a pre-PD history of an ICD; personal or family history of substance abuse, bipolar disorder, or gambling problems; and impulsive personality traits. Dysregulation of the mesocorticolimbic dopamine system is thought to be the major neurobiological substrate for ICDs in PD, but there is preliminary evidence for alterations in opiate and serotonin systems too. The primary treatment of ICDs in PD is discontinuation of the offending treatment, but not all patients can tolerate this due to worsening motor symptoms or DA withdrawal syndrome. While psychiatric medications and psychosocial treatments are frequently used to treat ICDs in the general population, there is limited empirical evidence for their use in PD, so it is critical for patients to be monitored closely for ICDs from disease onset and routine throughout its course. In the future, it may be possible to use a precision medicine approach to decrease the incidence of ICDs in PD by avoiding DA use in patients determined to be at highest risk based on their clinical and neurobiological (e.g., motor presentation, behavioral measures of medication response, genetics, dopamine transporter neuroimaging) profile. Additionally, as empirically validated treatments for ICDs and similar disorders (e.g., substance use disorders) emerge, it will also be important to examine their efficacy and tolerability in individuals with comorbid PD.

Revisiting the Medical Management of Parkinson's Disease: Levodopa versus Dopamine Agonist

The optimal treatment strategy for Parkinson's disease has been debated for decades. The introduction of levodopa (LD) treatment is frequently delayed because of theoretical concerns about its toxicity or the risk of drug-induced motor complications. These concerns have resulted in "LD phobia" with clinicians selecting dopamine agonist (DA) over LD as initial therapy. More recently, a shift in the treatment approach towards initial LD use appears to be occurring. It is therefore necessary to review current evidence for the use of LD and DA. This review discusses the medical management of Parkinson's disease with regards to the use of LD versus DA. Pendulum swings in treatment strategies between LD-first and DA-first therapies should be avoided. A balanced perspective is needed as there is a place for both drugs in the management of PD.

Pramipexole Increases Go Timeouts but Not No-go Errors in Healthy Volunteers

Parkinson's disease (PD) is characterized by motor symptoms, such as resting tremor, bradykinesia and rigidity, but also features non-motor complications. PD patients taking dopaminergic therapy, such as levodopa but especially dopamine agonists (DAs), evidence an increase in impulse control disorders (ICDs), suggesting a link between dopaminergic therapy and impulsive pursuit of pleasurable activities. However, impulsivity is a multifaceted construct. Motor impulsivity refers to the inability to overcome automatic responses or cancel pre-potent responses. Previous research has suggested that PD patients, on dopaminergic medications, have decreased motor impulsivity. Whether effects on impulsivity are main effects of dopaminergic therapies or are specific to PD is unclear. Using a Go No-go task, we investigated the effect of a single dose of the DA pramipexole on motor impulsivity in healthy participants. The Go No-go task consisted of Go trials, for which keystroke responses were made as quickly as possible, and lesser frequency No-go trials, on which motor responses were to be inhibited. We hypothesized that pramipexole would decrease motor impulsivity. This would manifest as: (a) fewer No-go errors (i.e., fewer responses on trials in which a response ought to have been inhibited); and (b) more timed-out Go trials (i.e., more trials on which the deadline elapsed before a decision to make a keystroke occurred). Healthy volunteers were treated with either 0.5 mg of pramipexole or a standard placebo (randomly determined). During the 2-h wait period, they completed demographic, cognitive, physiological and affective measures. The pramipexole group had significantly more Go timeouts (p < 0.05) compared to the placebo group though they did not differ in percent of No-go errors. In contrast to its effect on pursuit of pleasurable activities, pramipexole did not increase motor impulsivity. In fact, in line with findings in PD and addiction, dopaminergic therapy might increase motor impulse control. In these patient groups, by enhancing function of the dorsal striatum (DS) of the basal ganglia in contrast to its effect on impulsive pursuit of pleasurable activities. These findings have implications for use and effects of pramipexole in PD as well as in other conditions (e.g., restless leg, dystonia, depression, addiction-related problems).

Introduction to Parkinson disease (PD) and its complications

Parkinson disease (PD) is a common neurodegenerative disorder in older adults characterized by motor and nonmotor symptoms and complications. Impulse control disorders (ICDs), such as pathological gambling, compulsive shopping, compulsive sexual behavior (hypersexuality), and binge eating disorder, affect 13.6% of the PD population. Use of dopamine receptor agonists (DRAs) is considered a major risk factor for ICD development. Amantadine and a high dose of levodopa were linked to ICDs to a lesser extent than DRAs. Based on the severity of behavior(s), ICDs can negatively impact social, professional, and familial lives of patients and their families. Ideally, all PD patients taking DRAs, high doses of levodopa, and/or amantadine should be routinely asked about or monitored for ICDs during therapy initiation and continuation. Dose decrease or withdrawal of the offending agent, primarily DRAs, is usually the most effective first step in ICD management. Careful dose adjustment with close monitoring is warranted due to risk for worsening of motor symptoms or emergence of dopamine agonist withdrawal syndrome (DAWS). About 1/3 of PD patients with ICD who decrease or discontinue DRA experienced DAWS. The lowest dose of DRA will need to be continued to balance ICDs and DAWS as it is not alleviated by other dopaminergic or psychotropic medications. Other therapies with low empiric evidence, such as amantadine, naloxone, cognitive behavior therapy, deep brain stimulation, and psychopharmacotherapy showed mixed results for ICD management. It is crucial that clinicians are familiar with the psychiatric complications of PD, including ICDs, beyond mere recognition and management of motor symptoms.

Psychosis and concurrent impulse control disorder in Parkinson's disease: A review based on a case report

Psychosis, impulse control disorders (e.g., pathological gambling and hypersexuality) and repetitive behaviors such as punding are known psychiatric complications of Parkinson's disease (PD). Impulsive, compulsive and repetitive behaviors are strongly associated with dopamine-replacement therapy. We present the case of a 58-year-old man with PD and a myriad of psychiatric symptoms. Concurrent psychosis, punding and pathological gambling developed more than six years after the introduction of pramipexole and ceased shortly after the addition of quetiapine and discontinuation of pramipexole. This report emphasizes the importance of monitoring for a wide array of psychiatric symptoms in patients on dopamine replacement therapy.

Dopaminergic Medication in Parkinson's Disease and Problem Gambling

Studies on Parkinson's disease patients on dopaminergic medication report elevated rates of problem gambling. Results suggest changes in gambling behaviour are associated with the commencement and termination of dopaminergic medication implying a direct causal relationship. However, previous reports have not controlled for possible factors independent of dopamine medication contributing to the onset of problem gambling. This study aimed to explore the temporal relationships between problem gambling and dopamine medication taking into account premorbid gambling risk factors in a sample of Parkinson's disease patients. Twenty patients with Parkinson's disease meeting criteria for moderate risk or problem gambling were compared to twenty patients with Parkinson's disease who did not meet such criteria. The cross-sectional research design compared between group qualitative and quantitative differences. Participants completed an in-depth interview and timeline follow back, and battery of psychometric measures assessing impulsivity, gambling status, affective states, and obsessionality. Results revealed a complex and varied temporal relationship between dopaminergic medication onset and gambling. A small number of participants manifested excessive gambling following dopaminergic medication, with some ceasing on reduction in dosage or change in agonist class. Many demonstrated a range of individual and situational characteristic similar to problem gamblers in the general population, and in older adults with gambling problems. The obtained results provide a better understanding of the role of dopaminergic medication in problem gambling. Such findings have theoretical relevance to the reward deficiency model of gambling and have implications for the treatment of pathological gambling in PD and the general community.

Publicity and reports of behavioral addictions associated with dopamine agonists

Background The development of behavioral addictions (BAs) in association with dopamine agonists (DAs, commonly used to treat Parkinson's disease) has been reported. A recent report presented data that these associations are evident in the US Food and Drug Administration's (FDA) Adverse Event Reporting System (FAERS), a database containing information on adverse drug event and medication error reports submitted to the FDA. However, given that vulnerability to publicity-stimulated reporting is a potential limitation of spontaneous reporting systems like the FAERS, the potential impact of publicity on reporting in this case remains unclear. Method and aims To investigate the potential impact of publicity on FAERS reporting of BAs in association with DAs (BAs w/DAs) as presented by Moore, Glenmullen, and Mattison (2014) , news stories covering a BA/DA association were identified and compared with BA w/DA and other reporting data in the FAERS. Results Fluctuations in the growth of BA w/DA reporting to the FAERS between 2003 and 2012 appear to coincide with multiple periods of intensive media coverage of a BA/DA association, a pattern that is not evident in other reporting data in the FAERS. Discussion/Conclusions Publicity may stimulate reporting of adverse events and premature dismissal of the potential influence of publicity on reporting may lead to mistaking an increased risk of an adverse event being reported for an increased risk of an adverse event occurring.

The prevalence and clinical characteristics of hypersexuality in patients with Parkinson's disease following dopaminergic therapy: A systematic literature review

INTRODUCTION

A range of impulse control disorders have been identified as possible behavioural effects of brain dopamine replacement therapy (DRT) in patients with Parkinson's disease (PD). Among the behavioural problems associated with dysregulation of dopaminergic pathways underlying reward processing, hypersexuality carries significant social and legal repercussions, in addition to embarrassment for the patient with PD and his/her family. The present article evaluates the prevalence and characteristics of hypersexuality in the context of PD, focusing on the best available evidence.

METHODS

We conducted a systematic literature review according to the Prisma guidelines on large-scale epidemiological studies (n > 250) assessing hypersexuality in patients with PD treated with DRT.

RESULTS

Our systematic literature review identified 10 relevant studies characterised by medium-to-large sample sizes (n = 268-3090). Average lifetime prevalence of hypersexuality in patients with PD on DRT was found to be 2.7% (7.4% in patients on dopamine agonists). In general, hypersexuality was associated with male gender and higher doses of dopamine agonists. Other clinically relevant associations included younger age, earlier PD onset and history of behavioural symptoms prior to dopamine agonist use.

CONCLUSION

Hypersexuality is not rare in patients with PD treated with DRT, particularly in those on dopamine agonists. These findings indicate that PD specialists should regularly screen and monitor for hypersexuality, paying particular attention to younger male patients, with an early PD onset and previous history of behavioural problems.

Pathological Gambling Associated With Aripiprazole or Dopamine Replacement Therapy: Do Patients Share the Same Features? A Review

BACKGROUND

In the last 10 years, dopamine replacement therapy (DRT) has become a well-known risk factor for developing an impulse control disorder, such as gambling disorder (GD). Another medication, aripiprazole (ARI), has been more recently identified as another risk factor. Dopamine replacement therapy and ARI share a dopamine agonist action. Our work aimed at comparing patients with PG according to their treatment with DRT or ARI.

METHODS

Two methods were combined-a systematic review concentrated on case reports and the analysis of a French disordered gamblers cohort focused on patients using ARI or DRT at inclusion.

RESULTS

We reported 48 cases of GD possibly due to DRT and 17 cases of GD possibly due to ARI. Because of their standardized assessment, only the EVALJEU patients could be compared. Two clinical patterns emerged. Patients in the ARI group were young, impulsive, and high novelty seekers and had a history of substance misuse. Their first gambling experience occurred during adolescence. Conversely, patients in the DRT group were old, and they began gambling late in life. They showed low levels of gambling-related cognition.

CONCLUSIONS

Patients in the ARI group seemed to be more severe pathological gamblers than patients in the DRT group. Aripiprazole is a partial D2 receptor agonist, whereas DRT includes full D2 receptor agonist. The trigger mechanism of PG development is complex and cannot only be attributed only to the pharmacodynamic effects of dopaminergic drugs. Indeed, individual vulnerability factors and environmental factors need to be considered.

A review of adverse events linked to dopamine agonists in the treatment of Parkinson's disease

INTRODUCTION

Dopamine agonists are highly effective as adjunctive therapy to levodopa in advanced Parkinson's disease. These drugs have rapidly gained popularity as a monotherapy in the early stages of Parkinson's disease for patients less than 65-70 years old since they are about as effective as levodopa but patients demonstrate a lower tendency to develop motor complications. However, dopamine agonists could have peripheral and central side-effects which are often the reason for the discontinuation of the treatment.

AREAS COVERED

This article presents an overview of the efficacy and the potential negative effects related to the use of dopamine agonists in the treatment of Parkinson's disease.

EXPERT OPINION

Beyond the new generation non ergot dopamine agonists, no strong evidences allow the choice of a specific dopamine agonists for Parkinson 's disease treatment and by now dopamine agonists treatment should be tailored on specific adverse events profile.

When performance and risk taking are related: Working for rewards is related to risk taking when the value of rewards is presented briefly

Valuable monetary rewards can boost human performance on various effortful tasks even when the value of the rewards is presented too briefly to allow for strategic decision making. However, the mechanism by which briefly-presented reward information influences performance has remained unclear. One possibility is that performance after briefly-presented reward information is primarily boosted via activation of the dopamine reward system, whereas performance after very visible reward information is driven more by strategic processes. To examine this hypothesis, we first presented participants with a task in which they could earn rewards of relatively low (1 cent) or high (10 cents) value, and the value information was presented either briefly (17 ms) or for an extended duration (300 ms). Furthermore, responsiveness of the dopamine system was indirectly estimated with a measure of risk taking, the Balloon Analogue Risk Task (BART). Results showed that performance after high- compared to low-value rewards was indeed related to the BART scores only when reward information was presented briefly. These results are suggestive of the possibility that brief presentation of reward information boosts performance directly via activating the dopamine system, whereas extended presentation of reward information leads to more strategic reward-driven behavior.

No Evidence of Association between Toxoplasma gondii Infection and Financial Risk Taking in Females

Background

Past research linked Toxoplasma gondii (TG) infection in humans with neurological and mental disorders (e.g., schizophrenia, Alzheimer’s disease and attention disorders), irregularities of the dopaminergic and testosterone system, and increased likelihood of being involved in traffic accidents.

Methodology/Principal Findings

We test for an association between TG infection and financial decision-making (DM) using a case-control design in a sample of female Czech students (n = 79). We estimate each subject's risk attitude and loss aversion using an experimental economic task involving real monetary incentives. We find no significant evidence that either measure of decision-making is associated with TG infection.

Conclusion

We were unable to find evidence of an association between TG infection and financial decision-making in females.

The agony of the agonists: a review of impulsivity and withdrawal syndromes in Parkinson's disease treatment

The introduction of dopamine agonists was a welcome development in the treatment of Parkinson's disease. However, their history has been somewhat checkered with concerns about their side effects including sudden onset of sleep and ‘sleep attacks’ the development of fibrotic side effects with ergot-derived agents; and most recently, the emergence of impulse control disorders. Furthermore, those who develop these behaviors are those most likely to suffer distressing side effects on their withdrawal: the so-called ‘dopamine agonist withdrawal syndrome’ (DAWS). This review examines this complex area and some suggested strategies to avoid and manage these phenomena, and concludes with some discussion of the future agenda for improving the understanding and management of these conditions.

Therapeutic strategies to prevent and manage dyskinesias in Parkinson's disease

INTRODUCTION

Chronic treatment with levodopa is associated with the development of motor fluctuations and dyskinesias particularly in young Parkinson patients. In some cases, dyskinesias become so severe that they interfere with normal movement and negatively impact quality of life.

AREAS COVERED

In this review, we discuss benefits and limits of available therapeutic approaches aimed at delaying or managing dyskinesias as well as new strategies that are currently under investigation.

EXPERT OPINION

Among available treatments, monotherapy with dopamine agonists in the early phases of the disease reduces the risk for dyskinesias compared with levodopa. Nevertheless, dopamine agonists are unable to prevent dyskinesias once levodopa is added, which is always required once disease severity progresses. Convincing evidence of dyskinesia improvement has been shown only for deep brain stimulation and to some extent also for duodenal levodopa infusion and subcutaneous apomorphine. These approaches are expensive, have restrictive inclusion criteria and can cause potentially serious side effects. Alternative therapies include drugs targeting nondopaminergic neurotransmitter systems. Amantadine improves dyskinesias but its long-term effect is often unsatisfactory. Glutamatergic and gabaergic compounds have been tested in clinical trials, with promising results. By contrast, adrenergic drugs, fipamezole and idazoxan, did not show antidyskinetic effect.

Outcomes of Patients with Parkinson Disease and Pathological Gambling

Objective:

To determine the outcomes of patients with Parkinson disease (PD) with pathological gambling (PG) from one Canadian Movement Disorders Clinic.

Methods:

Assessments were performed in-person during routine clinic visits of all patients currently followed by one neurologist (OS). Pathological gambling was defined according to DSM-IV-TR criteria. Chart review was performed to obtain details on medication use, dosages, and patient demographics. Follow-up of patients with PG collected information on gambling behavior, PG management interventions, medications, treatment, and psychosocial outcomes.

Results:

146 patients were surveyed with an overall prevalence of PG of 4.1% (6/146). The rate of pathological gambling for those patients on dopamine agonist therapy (DA) was 8.1% (6/74). Only patients who were recreational gamblers prior to starting DA developed PG. All PG patients discontinued, decreased, or switched to another DA, and experienced a partial or full remission of PG. 3 (50%) patients described financial losses of $100,000 or more, and 75% (3/4) patients described significant marital stresses. At follow-up (August 2008), 4 of the 6 patients with PG continued to gamble in a controlled fashion despite medication changes. No significant difference in levodopa equivalent daily dose (LEDD) pre- and post-PG were observed; however, the relative amount of DA was decreased (p= 0.0593), while levodopa was relatively increased (p= 0.5277). Despite control of PG, patients still experience financial and marital strains.

Conclusions:

DA (in combination with levodopa) was associated with a significantly higher prevalence of PG in PD, particularly in patients who were recreational gamblers previously. Despite control of PG, patients continued to experience significant financial and marital stresses that should be regularly enquired upon in follow-up care and managed appropriately.

Pooled analysis of phase III with entacapone in Parkinson's disease

OBJECTIVES

To investigate efficacy and safety of entacapone across phase III studies in Parkinson's disease (PD) with wearing-off symptoms.

METHODS

Retrospective, pooled analysis of four phase 3 randomized, double-blind, placebo-controlled studies with entacapone.

RESULTS

475 of 808 patients with PD received entacapone and 333 received placebo. Entacapone improved daily OFF- and ON-times (change from baseline) by 0.8 h compared with placebo (P < 0.0001 for both variables). Entacapone was also better in UPDRS II (P < 0.01) and III (P < 0.01) scores and global evaluation (P < 0.05). Similar benefits were seen in subgroups of patients with and without dopamine agonist (DA) or selegiline, but the subgroup results should be regarded as exploratory. Entacapone was generally well tolerated. Dyskinesia and nausea were more frequently reported by patients on entacapone (25.7% and 14.5% of patients, respectively) than those receiving placebo (15.6% and 6.0%, respectively). However, there was no difference in reports of hallucinations between entacapone (4.8%) and placebo (4.8%).

CONCLUSIONS

Entacapone improved daily OFF- and ON-times by a mean of 0.8 h compared with placebo across the four pooled efficacy studies and was generally well tolerated. The results of this pooled analysis potentially serve as a useful benchmarking data for new therapies (especially levodopa products) in advanced patients with PD.

Therapeutic potential of metabotropic glutamate receptor 4-positive allosteric modulator TAS-4 in rodent models of movement disorders

Parkinson's disease (PD) is a very serious neurological disorder, and current methods of treatment fail to achieve long-term control. Previous studies suggest that stimulation of the metabotropic glutamate receptor 4 (mGluR4) represents a promising new approach to the symptomatic treatment of Parkinson's disease (PD). Preclinical models using both agonists and positive allosteric modulators of mGluR4 have demonstrated the potential for this receptor for the treatment of PD. In the present study, we describe the pharmacological characterization of an mGluR4 PAM, N-(2, 4-dichlorophenyl) pyridine-2-carboxamide (TAS-4), in several rodent PD models. TAS-4 is a potent and selective mGluR4 PAM of the human mGluR4 receptor (EC50- 287.8nM). TAS-4 showed efficacy alone or when administered in combination with l-DOPA. When administered alone, TAS-4 exhibited efficacy in reversing haloperidol-induced catalepsy. In addition, acute TAS-4 dose-dependently potentiated contralateral turning behavior induced by a threshold dose of l-3,4-dihydroxyphenylalanine (l-DOPA, 4mg/kg i.p.), a classical test for antiparkinson drug screening. Subchronic (28days, twice a day) TAS-4 (10mg/kg i.p.)+l-DOPA (4mg/kg i.p.) did not induce sensitization to turning behavior or abnormal involuntary movements during the course of treatment. Moreover, subchronic administration of a fully effective dose of l-DOPA (8mg/kg i.p.) significantly induces sensitization to turning behavior or abnormal involuntary movements. Results showed that TAS-4, in association with a low dose of l-DOPA, displayed antiparkinsonian activity similar to that produced by a full dose of l-DOPA without exacerbating abnormal motor side effects.

Gambling disorder during dopamine replacement treatment in Parkinson's disease: a comprehensive review

Gambling Disorder (GD) is characterized by “the failure to resist gambling impulses despite severe personal, family or occupational consequences”. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), GD replaces the DSM-IV diagnosis of Pathological Gambling (PG). GD estimated prevalence ranges between 0.4% and 3.4% within the adult population and it seems to be more common in patients with Parkinson's disease (PD). In this population, GD recently has become more widely recognized as a possible complication of dopamine agonist (DA) therapy. This association has aroused great interest for the dramatic impact GD has on patients' quality of life. Management of PG in patients with PD could be demanding. It is based on patient and caregiver education, modification of dopamine replacement therapy, and in some cases psychoactive drug administration. In this review article, the authors provide an overview of GD pathogenesis during DA therapy as well as a summary of available treatment options.

Safety overview of FDA-approved medications for the treatment of the motor symptoms of Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is among the most common of the neurodegenerative disorders. Treatment is primarily focused on correcting neurotransmitter imbalances. Several classes of medication are available for this purpose.

AREAS COVERED

A Medline search was performed to gather information about the safety of the medications approved for the treatment of the motor symptoms of PD. This was supplemented with additional articles obtained from online sources and information provided by the FDA and the manufacturers. The focus of this review is the side-effect and safety profiles of carbidopa/levodopa, dopamine agonists, selective monoamine oxidase inhibitors, catechol-o-methyltransferase inhibitors, anticholinergics and amantadine.

EXPERT OPINION

Though serious side-effects may occur, as a group, the medications used for the treatment of PD motor symptoms tend to produce side-effects that are mild to moderate in nature, and that primarily reflect the focus on dopaminergic therapies. Care plans for Parkinson's patients should be approached based on the needs of the individual as disease presentation, lifestyle, level of disability, concurrent disease states and the presence of non-motor symptoms make each case unique. Patients and caregivers must have realistic expectations about the use of PD medications.

Impulse control disorders in patients with dopamine agonist-treated prolactinomas and nonfunctioning pituitary adenomas: a case-control study

OBJECTIVE

We aimed to assess the prevalence of impulse control disorders (ICDs) in patients with prolactin-secreting adenomas treated with dopamine agonists (DAs), to identify associated factors and to compare it with a group of patients with nonfunctioning pituitary adenoma.

SUBJECTS, DESIGN AND MEASUREMENT

In a postal survey, 77 patients from Group A (patients with prolactinomas and present or past use of DAs) and 70 patients from Group B (patients with nonfunctioning pituitary adenoma and no history of DA therapy) responded to a questionnaire on compulsive shopping, pathologic gambling, hypersexuality and punding. Associated clinical information was obtained through the survey and review of medical electronic records.

RESULTS

The total ICD prevalence was 24·68% in Group A and 17·1% in Group B (P = 0·31). Group A had an increased rate of hypersexuality (P = 0·03). Subgroup analysis revealed that men in Group A had a significantly increased frequency of total ICDs when compared with men in Group B (27·7 vs 3·7%, P = 0·01). No differences in rates of total ICDs were found between women of Groups A and B (20 vs 25·6%, P = 0·78). No association with type, dose or duration of treatment with DA was noted.

CONCLUSIONS

Males with prolactinomas treated with DAs were 9·9 times more likely to develop an ICD than their counterparts with nonfunctioning pituitary adenomas. Until prospective studies on the relationship of DA use in patients with prolactinoma and ICDs are available, the authors propose that patients with prolactinoma be forewarned of possible ICD development with DA therapy.