Early treatment of Parkinson's disease with cabergoline delays the onset of motor complications. Results of a double-blind levodopa controlled trial. The PKDS009 Study Group

Dose-response relationship of levodopa with dyskinesia in Parkinson's disease: A systematic review and meta-analysis

Despite existing evidence linking dyskinesia to levodopa, the primary treatment for Parkinson's, the dose-response relationship and risk factors remain uncertain. In this study, the risk for dyskinesia in patients with Parkinson's disease receiving levodopa was evaluated via meta-analysis and meta-regression approaches to examine dyskinesia risk factors more reliably and improve treatment strategies and patient care. The PubMed and Embase databases were searched to identify randomized controlled trials comparing levodopa with other anti-Parkinson's drugs published in English before June 31, 2023. The primary outcome was dyskinesia, and a risk of bias assessment was performed. In total, 24 studies met the inclusion criteria; 21 had a low risk of bias, and 3 had a high risk of bias. These studies included 4698 patients with Hoehn and Yahr Grade I-III Parkinson's disease. Our meta-analysis showed that the risk of dyskinesia was higher for levodopa than for other anti-Parkinson's drugs (odds ratio: 2.52 [95% confidence interval: 1.84-3.46]). Dyskinesia was not related to age (slope coefficient: 0.185 [0.095]; P = 0.061), disease duration (slope coefficient: 0.011 [0.018]; P = 0.566), or treatment duration (slope coefficient: 0.008 [0.007]; P = 0.216). The mean levodopa equivalent dose (slope coefficient: 0.004 [0.001]; P = 0.001) in the experimental group and the differences in drug doses between the experimental and control groups were correlated with the risk of dyskinesia. Results of randomized controlled trials supported an association between the levodopa dose and dyskinesia in patients with Parkinson's disease. Compared with levodopa users, users of other anti-Parkinson's drugs had a lower incidence of dyskinesia. Age, disease duration, and treatment duration were not correlated with dyskinesia. These findings suggest that anti-Parkinson's drugs other than levodopa, particularly in cases of early-stage Parkinson's disease, should be considered to reduce the risk of dyskinesia.

The Dynamics of Dopamine D2 Receptor-Expressing Striatal Neurons and the Downstream Circuit Underlying L-Dopa-Induced Dyskinesia in Rats

L-dopa (l-3,4-dihydroxyphenylalanine)-induced dyskinesia (LID) is a debilitating complication of dopamine replacement therapy for Parkinson's disease. The potential contribution of striatal D2 receptor (D2R)-positive neurons and downstream circuits in the pathophysiology of LID remains unclear. In this study, we investigated the role of striatal D2R+ neurons and downstream globus pallidus externa (GPe) neurons in a rat model of LID. Intrastriatal administration of raclopride, a D2R antagonist, significantly inhibited dyskinetic behavior, while intrastriatal administration of pramipexole, a D2-like receptor agonist, yielded aggravation of dyskinesia in LID rats. Fiber photometry revealed the overinhibition of striatal D2R+ neurons and hyperactivity of downstream GPe neurons during the dyskinetic phase of LID rats. In contrast, the striatal D2R+ neurons showed intermittent synchronized overactivity in the decay phase of dyskinesia. Consistent with the above findings, optogenetic activation of striatal D2R+ neurons or their projections in the GPe was adequate to suppress most of the dyskinetic behaviors of LID rats. Our data demonstrate that the aberrant activity of striatal D2R+ neurons and downstream GPe neurons is a decisive mechanism mediating dyskinetic symptoms in LID rats.

Drug Repositioning Based on the Enhanced Message Passing and Hypergraph Convolutional Networks

Drug repositioning, an important method of drug development, is utilized to discover investigational drugs beyond the originally approved indications, expand the application scope of drugs, and reduce the cost of drug development. With the emergence of increasingly drug-disease-related biological networks, the challenge still remains to effectively fuse biological entity data and accurately achieve drug-disease repositioning. This paper proposes a new drug repositioning method named EMPHCN based on enhanced message passing and hypergraph convolutional networks (HGCN). It firstly constructs the homogeneous multi-view information with multiple drug similarity features and then extracts the intra-domain embedding of drugs through the combination of HGCN and channel attention mechanism. Secondly, inter-domain information of known drug-disease associations is extracted by graph convolutional networks combining node and edge embedding (NEEGCN), and a heterogeneous network composed of drugs, proteins and diseases is built as an important auxiliary to enhance the inter-domain message passing of drugs and diseases. Besides, the intra-domain embedding of diseases is also extracted through HGCN. Ultimately, intra-domain and inter-domain embeddings of drugs and diseases are integrated as the final embedding for calculating the drug-disease correlation matrix. Through 10-fold cross-validation on some benchmark datasets, we find that the AUPR of EMPHCN reaches 0.593 (T1) and 0.526 (T2), respectively, and the AUC achieves 0.887 (T1) and 0.961 (T2) respectively, which shows that EMPHCN has an advantage over other state-of-the-art prediction methods. Concerning the new disease association prediction, the AUC of EMPHCN through the five-fold cross-validation reaches 0.806 (T1) and 0.845 (T2), which are 4.3% (T1) and 4.0% (T2) higher than the second best existing methods, respectively. In the case study, EMPHCN also achieves satisfactory results in real drug repositioning for breast carcinoma and Parkinson's disease.

Clinical Pharmacology of Entacapone (Comtan) From the FDA Reviewer

This new drug application was first submitted to the US Food and Drug Administration (FDA) by the Orion Corporation from Finland on January 2, 1998. The final clinical pharmacology review was completed on September 3, 1999. Entacapone is a potent and specific peripheral catechol-O-methyltransferase inhibitor. It has been shown to improve the clinical benefits of levodopa plus an aromatic L-amino acid decarboxylase inhibitor when given to patients with Parkinson's disease and end-of-dose deterioration in the response to levodopa (the "wearing-off" phenomenon). The drug indication is for Parkinson's disease as an adjunct therapy to levodopa/carbidopa. This is a combination drug with carbidopa (aromatic amino acid decarboxylation inhibitor) and entacapone. It is rapidly absorbed after oral administration of a single dose, with peak time generally reached within 1 hour. It is noted that no accumulation of plasma entacapone was detected after 8 daily doses. The maximum daily dose is 2000 mg. In this paper, the clinical pharmacology review of the drug is presented from the perspective of a clinical pharmacologist who reviewed this new drug application at the FDA. It should be noted that all the information in this paper is publicly available on the FDA website and in its literature.

Exosomes in Parkinson: Revisiting Their Pathologic Role and Potential Applications

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by bradykinesia, rigidity, and tremor. Considerable progress has been made to understand the exact mechanism leading to this disease. Most of what is known comes from the evidence of PD brains' autopsies showing a deposition of Lewy bodies-containing a protein called α-synuclein (α-syn)-as the pathological determinant of PD. α-syn predisposes neurons to neurotoxicity and cell death, while the other associated mechanisms are mitochondrial dysfunction and oxidative stress, which are underlying precursors to the death of dopaminergic neurons at the substantia nigra pars compacta leading to disease progression. Several mechanisms have been proposed to unravel the pathological cascade of these diseases; most of them share a particular similarity: cell-to-cell communication through exosomes (EXOs). EXOs are intracellular membrane-based vesicles with diverse compositions involved in biological and pathological processes, which their secretion is driven by the NLR family pyrin domain-containing three proteins (NLRP3) inflammasome. Toxic biological fibrils are transferred to recipient cells, and the disposal of damaged organelles through generating mitochondrial-derived vesicles are suggested mechanisms for developing PD. EXOs carry various biomarkers; thus, they are promising to diagnose different neurological disorders, including neurodegenerative diseases (NDDs). As nanovesicles, the applications of EXOs are not only restricted as diagnostics but also expanded to treat NDDs as therapeutic carriers and nano-scavengers. Herein, the aim is to highlight the potential incrimination of EXOs in the pathological cascade and progression of PD and their role as biomarkers and therapeutic carriers for diagnosing and treating this neuro-debilitating disorder.

The effect and safety of levodopa alone versus levodopa sparing therapy for early Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

The best choice between levodopa alone and levodopa sparing medications for early Parkinson's disease (PD) remains controversial. We aimed to evaluate the effect and safety of levodopa alone and levodopa sparing therapy in symptom relief, neuroimage results and complications.

METHODS

A systematic search was performed in PubMed, The Cochrane Library, EMBASE, and Web of Science for randomized controlled trials of early PD patients comparing levodopa-alone with levodopa-sparing therapy. The mean difference (MD) and the risk ratio (RR) were meta-analyzed.

RESULTS

Twenty-three articles with 4913 patients were included. Significantly greater benefit was detected for the levodopa group in the changes of Unified Parkinson's Disease Rating Scale part II (p < 0.00001), III (p < 0.00001), and total (p < 0.00001) scores, and the between-group MD in part III score increased over time. The loss of the radioligands uptake in levodopa-alone group was also increasingly greater over time. Patients treated with levodopa alone were at higher risk for wearing-off (p < 0.001) and dyskinesia (p < 0.001), but the RR for dyskinesia between the two groups decreased after 2 years of follow-up.

CONCLUSION

Levodopa-alone therapy might be superior in motor symptom relief than levodopa-sparing therapy for early PD patients, and the motor advantage of levodopa-alone might grow over time. Sparing therapy might be associated with less risk of wearing-off and dyskinesia, but the events between the two groups might not be different in the long run. Overall, levodopa alone therapy might bring more net benefit to early PD patients compared with levodopa sparing strategies. The clinical and imaging findings are conflicting, which requires further investigation.

Liposomes: Novel Drug Delivery Approach for Targeting Parkinson's Disease

Parkinson's disease is one of the most severe progressive neurodegenerative disorders, having a mortifying effect on the health of millions of people around the globe. The neural cells producing dopamine in the substantia nigra of the brain die out. This leads to symptoms like hypokinesia, rigidity, bradykinesia, and rest tremor. Parkinsonism cannot be cured, but the symptoms can be reduced with the intervention of medicinal drugs, surgical treatments, and physical therapies. Delivering drugs to the brain for treating Parkinson's disease is very challenging. The blood-brain barrier acts as a highly selective semi-permeable barrier, which refrains the drug from reaching the brain. Conventional drug delivery systems used for Parkinson's disease do not readily cross the blood barrier and further lead to several side-effects. Recent advancements in drug delivery technologies have facilitated drug delivery to the brain without flooding the bloodstream and by directly targeting the neurons. In the era of Nanotherapeutics, liposomes are an efficient drug delivery option for brain targeting. Liposomes facilitate the passage of drugs across the blood-brain barrier, enhances the efficacy of the drugs, and minimize the side effects related to it. The review aims at providing a broad updated view of the liposomes, which can be used for targeting Parkinson's disease.

Patterns and Determinants of Prescribing for Parkinson's Disease: A Systematic Literature Review

Since the discovery of levodopa (L-dopa) in 1967, the range of medications available to treat Parkinson's disease has increased significantly and guidance on the use, efficacy, and safety of these medications has evolved. To assess levels of adherence to national prescribing guidelines and awareness of changes in the efficacy and safety data published in the profiles of medications for the treatment of PD, we have reviewed studies on patterns and determinants of prescribing PD medications conducted in the last 50 years (since the discovery of L-dopa). A systematic literature review was conducted using EMBASE (1967 to March, 2018), Ovid MEDLINE(R) ALL (1967 to March 16, 2018), PsycINFO (1967 to the 2nd week of March, 2018), and PubMed to identify all studies measuring prescribing patterns of PD medication between 1967 and 2017. Study design, source of data, country, year of study, number of patients and/or prescriptions, unit of analysis, prescribing determinants, and percentage utilisation of PD medications were extracted where possible. 44 studies examining prescribing patterns and/or prescribing determinants across 17 countries were identified. Unsurprisingly, L-dopa was the most commonly prescribed medication in all studies, accounting for 46.50% to 100% of all prescriptions for PD. In several studies, the prescribing rate of ergot-derived dopamine agonists (DAs) decreased over time in concordance with guidance. In contrast, the prescribing rates of non-ergot DAs increased over the last ten years in most of the included studies. In examining prescribing factors, two major categories were exemplified, patients' factors and prescribers' factors, with patients' age being the most common factor that affected the prescription in most studies. In conclusion, L-dopa is now the most commonly prescribed medication for cases of PD but there is large variation in the prescribing rates of catechol-O-methyltransferase (COMT) inhibitors, monoamine oxidase B (MAO-B) inhibitors, amantadine, and anticholinergics between countries. New studies examining the effects of recent clinical trials and measuring the prescribing rates of newly approved medications are warranted.

Factors to Consider in the Selection of Dopamine Agonists for Older Persons with Parkinson's Disease

Dopamine agonists (DAs) are frequently used in the management of Parkinson's disease (PD), a complex multisystem disorder influenced substantially by age-related factors. Over 80% of PD patients present after age 60 years and may have clinical features exacerbated by age-related comorbidities or decline in physiological compensatory mechanisms. Pharmacotherapy for motor symptoms in older persons is more likely to involve exclusive use of levodopa combined with a peripheral decarboxylase inhibitor throughout the course of the illness. Non-ergot DAs, such as pramipexole, rotigotine and ropinirole, may be used as de novo monotherapy for the control of motor symptoms in older persons, although they are less efficacious than levodopa therapy. DAs may also be considered as adjunct therapy in older persons when motor symptoms are no longer adequately controlled by levodopa or when motor fluctuations and dyskinesia appear. DAs may be used cautiously in older persons with cognitive impairment and orthostatic hypotension but should be avoided when there is a history or risk of psychosis or impulse control disorders.

'Levodopa Phobia': a review of a not uncommon and consequential phenomenon

'Levodopa Phobia' is under-recognised in Parkinson's disease but can cause profound detrimental clinical complications if left to continue. Several types can be encountered in clinical practice and can be driven by a misplaced fear of levodopa-induced dyskinesias, other gastrointestinal side effects and also the theoretical notion that levodopa may be toxic to dopaminergic neurons in the brain. The condition can be underpinned by a sense of strong influence from the physicians or carers who are unwilling to prescribe or consider levodopa, and also high levels of anxiety or even impulsive compulsive traits in patients who have been influenced by available literature or social media-based information. If unrecognised, the clinical issue may lead to motor deterioration and related muscle contractures leading to social isolation as well as a range of non-motor symptoms. In some, there may be emergence of intrusive impulse control disorders because of reliance on only dopamine agonists related to the fear of taking levodopa. Four cases illustrate the different patterns of 'Levodopa Phobia' in this study. Management of levodopa phobia is complex and includes recognition and skilled neuropsychological interventions to break the misperceptions about the complications of levodopa therapy.

Does Late Levodopa Administration Delay the Development of Dyskinesia in Patients with De Novo Parkinson's Disease?

BACKGROUND

It remains controversial whether late levodopa administration is a reasonable approach to reducing the risk of levodopa-induced dyskinesia in Parkinson's disease.

OBJECTIVE

This study aimed to investigate the effects of levodopa sparing on the development of levodopa-induced dyskinesia.

METHODS

We retrospectively reviewed medical records for patients with de novo Parkinson's disease who visited the Yonsei Parkinson Center between April 2009 and June 2015 and received at least 2 years of treatment. Among 657 patients with drug-naïve Parkinson's disease who met the study criteria, 90 were initially treated with dopamine agonists (levodopa-sparing group; levodopa supplementation after 2.15 years). Another 90 patients who were initially treated with levodopa (levodopa group) were matched to the 90 patients for age, sex, follow-up duration, Parkinson's disease duration, Unified Parkinson's Disease Rating Scale Part III scores, and baseline dopamine transporter availability in the posterior putamen. The effects of levodopa sparing on dyskinesia development were assessed with Kaplan-Meier estimates and a stratified Cox regression model adjusted for age of onset, sex, dopamine transporter availability, and daily levodopa dose per weight.

RESULTS

The levodopa-sparing group had a comparable age of onset (54.80 ± 7.36 years) to the levodopa group (56.53 ± 6.16 years). The Kaplan-Meier analysis revealed that the risk of levodopa-induced dyskinesia after treatment initiation was similar between the groups. Once the levodopa-sparing group started levodopa supplementation, they had a higher risk of developing levodopa-induced dyskinesia. However, a stratified Cox regression model indicated that hazard ratios for levodopa sparing to levodopa-induced dyskinesia development were 0.138 (95% confidence interval 0.024-0.785) after treatment initiation and 0.438 (95% confidence interval 0.105-1.832) after levodopa initiation.

CONCLUSION

Late levodopa administration was associated with a low risk of dyskinesia after adjusting for confounding effects and may be a reasonable strategy for prolonging the levodopa-induced dyskinesia-free period in Parkinson's disease.

Molecular basis of dopamine replacement therapy and its side effects in Parkinson's disease

There is currently no cure for Parkinson's disease. The symptomatic therapeutic strategy essentially relies on dopamine replacement whose efficacy was demonstrated more than 50 years ago following the introduction of the dopamine precursor, levodopa. The spectacular antiparkinsonian effect of levodopa is, however, balanced by major limitations including the occurrence of motor complications related to its particular pharmacokinetic and pharmacodynamic properties. Other therapeutic strategies have thus been developed to overcome these problems such as the use of dopamine receptor agonists, dopamine metabolism inhibitors and non-dopaminergic drugs. Here we review the pharmacology and molecular mechanisms of dopamine replacement therapy in Parkinson's disease, both at the presynaptic and postsynaptic levels. The perspectives in terms of novel drug development and prediction of drug response for a more personalised medicine will be discussed.

Levodopa-induced dyskinesia in Parkinson's disease: still no proof? A meta-analysis

We investigated whether there is a linear relationship between levodopa (LD) dose and treatment duration, and the development of levodopa-induced dyskinesia (LID) among patients with early untreated Parkinson's disease (PD). We performed a meta-analysis of randomized-controlled trials (RCTs) comparing LD monotherapy to any other antiparkinsonian treatment in early PD patients. Meta-regressions were conducted including as covariates the effects of LD dose, treatment duration, and age. We further proceeded in subgroup analyses based on the type of medications in the non-LD monotherapy (control) group and on whether patients in the control group received additional levodopa or not. Thirteen eligible RCTs were included, which revealed a significantly higher risk for dyskinesia in patients initially treated with LD monotherapy compared to any other treatment (OR = 2.82). None of the subsequent meta-regressions revealed any significant relationship with dose, treatment duration or age. Patients treated on LD monotherapy or MAOΙ plus LD were at a greater risk to develop LID than patients who received DA only or DA plus supplemental LD. The increased heterogeneity compromised the robustness of the results. The alleged correlation between LID and LD dose and treatment duration cannot be verified based on the data available so far. Well-designed, large-scale, long-term, RCTs on drug-naïve PD patients could allow the better comprehension of the pattern of the association between LID and LD treatment parameters.

The effects of cysteamine in a mouse model of levodopa-induced dyskinesias

Levo-dopa (L-DOPA) has shown significant and long-lasting efficacy in the treatment of motor features characteristic of Parkinson's disease (PD). However, the effects tend to wear off at a time typically when side-effects, such as L-DOPA induced dyskinesias (LIDs), start to emerge and for which the treatment options are very limited. In recent years, we have reported on the neuroprotective and neurorestorative properties of the compounds cystamine/cysteamine in ameliorating several aspects of PD. Building on these observations, we set out to further evaluate the benefits of cysteamine on LIDs. We thus treated mice displaying LIDs with single cysteamine challenges at various doses (20, 50 and 30mg/kg) or chronically for 2 weeks using cysteamine at a dose of 30mg/kg. None of the regimens nor doses ameliorated any LID-related behavioral impairments. Mice displaying LIDs did, however, respond to a single treatment of 60mg/kg of amantadine, a drug used to clinically manage LIDs. Taken together, our results suggest that cysteamine does not induce benefits on LIDs, at least at the doses and regimen tested in our study. However, the disease-modifying effects depicted by cystamine/cysteamine, which we have shown in several reports, would strongly encourage its continued evaluation in the clinical setting.

Levodopa: History and Therapeutic Applications

Levodopa – the aromatic amino acid L-3,4–dihydroxy phenylalanine has held the attention of neurologists and pharmacologists alike for more than half a century. Even though extensive research has been done across the globe in treatment of Parkinson's disease, with different molecules, none could replace the gold standard treatment or provide complete relief for the debilitated. Although research brought us better tips and tricks to modulate the dopamine blood levels to balance between the desired and deleterious effects, it could never replace the basic substrate. From simple oral preparation to more advanced treatment like duodenal dopa administration for better efficacy and compliance, L-dopa has sure undergone scrutiny and stayed strong as the fundamental neurotransmitter replacement therapy to pave path for many more new therapeutic strategies. So as a token of gratitude to the revolutionary agent and pioneers behind it, a trip down the memory lane is in order.

Non-human primate models of PD to test novel therapies

Non-human primate (NHP) models of Parkinson disease show many similarities with the human disease. They are very useful to test novel pharmacotherapies as reviewed here. The various NHP models of this disease are described with their characteristics including the macaque, the marmoset, and the squirrel monkey models. Lesion-induced and genetic models are described. There is no drug to slow, delay, stop, or cure Parkinson disease; available treatments are symptomatic. The dopamine precursor, L-3,4-dihydroxyphenylalanine (L-Dopa) still remains the gold standard symptomatic treatment of Parkinson. However, involuntary movements termed L-Dopa-induced dyskinesias appear in most patients after chronic treatment and may become disabling. Dyskinesias are very difficult to manage and there is only amantadine approved providing only a modest benefit. In this respect, NHP models have been useful to seek new drug targets, since they reproduce motor complications observed in parkinsonian patients. Therapies to treat motor symptoms in NHP models are reviewed with a discussion of their translational value to humans. Disease-modifying treatments tested in NHP are reviewed as well as surgical treatments. Many biochemical changes in the brain of post-mortem Parkinson disease patients with dyskinesias are reviewed and compare well with those observed in NHP models. Non-motor symptoms can be categorized into psychiatric, autonomic, and sensory symptoms. These symptoms are present in most parkinsonian patients and are already installed many years before the pre-motor phase of the disease. The translational usefulness of NHP models of Parkinson is discussed for non-motor symptoms.

Comparison for Efficacy and Tolerability among Ten Drugs for Treatment of Parkinson's Disease: A Network Meta-Analysis

Parkinson’s disease (PD) is a long term disorder affects the central nervous system and we aim to determine the relative efficacy of the current available drugs used in PD. Firstly, we performed a systematic review in current literature and eligible studies were retrieved from online databases, relevant data were extracted. Efficacy of these medications was assessed by different Unified Parkinson’s Disease Rating Scales (UPDRS). Mean difference (MD) and odds ratio (OR) were produced by pairwise or network meta-analysis (NMA). Finally, we performed a cluster analysis for the included medications with respect to their surface under the cumulative ranking curve (SUCRA). Pairwise meta-analysis suggests that selegiline had a higher ranking in UPDRS II, UPDRS III and UPDRS total than bromocriptine and levodopa. Selegiline was more tolerable than bromocriptine (OR = 0.62, CI: 0.39 to 0.98) and pramipexole was less tolerable than levodopa (OR = 1.43, CI = 1.00 to 2.04). Results of NMA indicate that patients with levodopa, pramipexole, ropinirole and selegiline exhibited a significantly improved UPDRS III than those with lazabemide. To sum up, levodopa, selegiline, ropinirole and rotigotine were recommended for PD patients as they appeared relatively high efficacy and tolerability.

Recent progress in ergot alkaloid research

Ergot alkaloids are a class of indole derivatives produced by the genera of Ascomycota includingClaviceps,Aspergillus,Penicillium, andEpichloë.

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.

The impact of early versus late levodopa administration

Long-term levodopa therapy in patients with Parkinson's disease (PD) is associated with motor complications including motor fluctuations (MF) and levodopa-induced dyskinesias (LID). The time to appearance of MF and LID is apparently related to both the timing and the duration of levodopa therapy, but is highly variable. We performed a retrospective analysis of all levodopa-treated PD patients to explore the effect of time from PD onset to levodopa initiation on time to MF or LID. We used a Cox multivariate regression model after stratifying patients into four quartiles, according to the time to levodopa initiation. Data from 170 PD patients (117 males, age at onset: 65.1 ± 11.6 years, time to levodopa treatment: 23.8 ± 28.4 months) was included in the analysis. Early levodopa administration was associated with a shorter time from diagnosis to both MF (p < 0.001) and LID (p = 0.001). The hazard ratio to develop MF and LID from the time of PD diagnosis was 2.48 (p < 0.001) and 2.71 (p = 0.002), respectively. In our population, we found that delaying levodopa administration was associated with a longer time to the appearance of motor complications after diagnosis. While disease duration is the most important determinant of the onset of motor complications, delaying levodopa could prolong the 'complication-free' period.

Pramipexole v. Levodopa as Initial Treatment for Parkinson’s Disease: A Randomized Clinical-Economic Trial

Purpose. To determine the 2-year incremental cost effectiveness of initial pramipexole treatment compared with initial levodopa treatment in patientswith early Parkinson’s disease (PD). Methods. 301 subjects with early PD were randomized to either pramipexole or levodopa and followed every 3 months over a 2-year period. Costs were assigned to patient collected health utilization data using a variety of methods. Health state preferences were estimated using the EuroQol. Results. Pramipexole strategy was an estimated $2,138 (SE = $1,182) more expensive than levodopa strategy. The incremental cost-effectiveness of pramipexole compared with levodopa was $106,900/QALY (EQ-5D), compared with pramipexole being dominated by levodopa using the EQVAS. Conclusions.Although considerable uncertainty exists in the 2-year cost-effectiveness of initial pramipexole compared with initial levodopa in the treatment of early PD, our estimates suggest that pramipexole may not be welfare enhancing during the first 2 years of treatment. If initial pramipexole results in long-term improvements in quality of life, its cost-effectiveness will become more favorable.

How to optimize the treatment of early stage Parkinson's disease

The approach to early Parkinson's disease denotes the communication of the diagnosis and important decisions, such as when and how to start treatment. Evidence based medicine and guidelines indicate which drugs have robust evidence of efficacy and tolerability in this specific population. However, de-novo patients may show different characteristics and they may be in a different phase of their disease. In this review, we will give an insight into the appropriate time therapy should be started and the actual knowledge about disease modification therapies. Moreover, the drugs indicated for early treatment will be considered and an indication for the use of these drugs will be given with the support of the actual knowledge.

Dopamine agonists early monotherapy for the delay of development of levodopa-induced dyskinesias

Dyskinesias are common, often disabling motor complications emerging in Parkinson's disease following chronic levodopa treatment. Common views associate the development of dyskinesias both with progressive loss of striatal dopamine nerve terminals and with intermittent delivery of the short half-life levodopa. Thus, according to continuous dopaminergic stimulation theory, dopamine agonists having half-lifes longer than levodopa would minimize the risk of the development of dyskinesias. The article highlights some interesting aspects of the clinical trials testing dopamine agonists monotherapy as a strategy that can reduce the risk of motor complications, and raises some concerns in terms of their early use in Parkinson's disease treatment to prevent or delay dyskinesia. Finally, we emphasize the need for reconsideration of arguments against use of levodopa as a starting therapy for Parkinson's disease.

Progress in Clinical Neurosciences: A Forum on the Early Management of Parkinson's Disease

There are numerous concerns related to treatment choices involving early dopaminergic therapy in Parkinson's disease. These include the effect on the underlying progression of the neurodegenerative process as well as the development of motor complications such as fluctuations and dyskinesias. A number of recent basic and clinical studies have provided new insights but have also added confusion and controversy. This report summarizes presentations and discussion dealing with these issues from a one-day symposium involving Canadian Movement Disorders neurologists.

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.

An update on the management of young-onset Parkinson's disease

In the text that follows, we review the main clinical features, genetic characteristics, and treatment options for Parkinson's disease (PD), considering the age at onset. The clinical variability between patients with PD points at the existence of subtypes of the disease. Identification of subtypes is important, since a focus on homogenous group may lead to tailored treatment strategies. One of the factors that determine variability of clinical features of PD is age of onset. Young-onset Parkinson's disease (YOPD) is defined as parkinsonism starting between the ages of 21 and 40. YOPD has a slower disease progression and a greater incidence and earlier appearance of levodopa-induced motor complications; namely, motor fluctuations and dyskinesias. Moreover, YOPD patients face a lifetime of a progressive disease with gradual worsening of quality of life and their expectations are different from those of their older counterparts. Knowing this, treatment plans and management of symptoms must be paid careful attention to in order to maintain an acceptable quality of life in YOPD patients.

Impact of subthalamic nucleus stimulation on young-onset Parkinson's disease

Objective. To clarify the efficacy of subthalamic nucleus (STN) stimulation in young-onset Parkinson's disease (PD), we compared the effects of STN stimulation on the motor symptoms between young-onset PD (YOPD) and late-onset PD (LOPD). Methods. We analyzed the effects of STN stimulation on motor function and motor fluctuations in 15 patients with YOPD, and 113 patients with LOPD who underwent STN stimulation during the same period. The Unified Parkinson's Disease Rating Scale (UPDRS) was evaluated during the on-period and off-period, which are defined as the times at which the motor symptoms are the best and worst during the daily active time with sustaining anti-parkinsonian drugs. The dyskinesia severity rating scale (DSRS) also was employed to assess the severity of peak-dose dyskinesia. We analyzed the changes in levodopa equivalent daily dose (LED), motor fluctuations, DSRS, and UPDRS part 3 score after STN stimulation, and compared the changes in each score between the two groups (YOPD vs. LOPD). Results. The LED was reduced, and the on-off motor fluctuation index, dyskinesia rating scale score (on-period), and UPDRS part 3 score (on- and off-periods) were improved in both the YOPD and LOPD groups. The improvement rates of the UPDRS part 3 scores in both the on- and off-periods in the YOPD group were superior to those in the LOPD group. The results of multivariate logistic regression analysis demonstrated that YOPD itself is the best responder to STN stimulation. Conclusions. STN stimulation can reduce the LED and improve motor fluctuations in patients with YOPD. The effects of STN stimulation on the motor symptoms of YOPD patients are superior to those in LOPD. The present findings suggest that YOPD patients suffering from several problems related to pharmacological therapy are probably good candidates for STN stimulation.

Summary of the recommendations of the EFNS/MDS-ES review on therapeutic management of Parkinson's disease

OBJECTIVE

To summarize the 2010 EFNS/MDS-ES evidence-based treatment recommendations for the management of Parkinson's disease (PD). This summary includes the treatment recommendations for early and late PD.

METHODS

For the 2010 publication, a literature search was undertaken for articles published up to September 2009. For this summary, an additional literature search was undertaken up to December 2010. Classification of scientific evidence and the rating of recommendations were made according to the EFNS guidance. In cases where there was insufficient scientific evidence, a consensus statement ('good practice point') is made.

RESULTS AND CONCLUSIONS

For each clinical indication, a list of therapeutic interventions is provided, including classification of evidence.

Rebalance of striatal NMDA/AMPA receptor ratio underlies the reduced emergence of dyskinesia during D2-like dopamine agonist treatment in experimental Parkinson's disease

Dopamine replacement with levodopa (L-DOPA) represents the mainstay of Parkinson’s disease (PD) therapy. Nevertheless, this well established therapeutic intervention loses efficacy with the progression of the disease and patients develop invalidating side effects, known in their complex as L-DOPA-induced dyskinesia (LID). Unfortunately, existing therapies fail to prevent LID and very few drugs are available to lessen its severity, thus representing a major clinical problem inPDtreatment. D2-like receptor (D2R) agonists are a powerful clinical option as an alternative to L-DOPA, especially in the early stages of the disease, being associated to a reduced risk of dyskinesia development. D2R agonists also find considerable application in the advanced stages of PD, in conjunction with L-DOPA, which is used in this context at lower dosages, to delay the appearance and the extent of the motor complications. In advanced stages of PD, D2R agonists are often effective in delaying the appearance and the extent of motor complications. Despite the great attention paid to the family of D2R agonists, the main reasons underlying the reduced risk of dyskinesia have not yet been fully characterized. Here we show that the striatal NMDA/AMPAreceptor ratio and theAMPAreceptor subunit composition are altered in experimental parkinsonism in rats. Surprisingly, while L-DOPA fails to restore these critical synaptic alterations, chronic treatment with pramipexole is associated not only with a reduced risk of dyskinesia development but is also able to rebalance, in a dose-dependent fashion, the physiological synaptic parameters, thus providing new insights into the mechanisms of dyskinesia.

Drug-induced dyskinesia in Parkinson's disease. Should success in clinical management be a function of improvement of motor repertoire rather than amplitude of dyskinesia?

BACKGROUND

Dyskinesia, a major complication in the treatment of Parkinson's disease (PD), can require prolonged monitoring and complex medical management.

DISCUSSION

The current paper proposes a new way to view the management of dyskinesia in an integrated fashion. We suggest that dyskinesia be considered as a factor in a signal-to-noise ratio (SNR) equation where the signal is the voluntary movement and the noise is PD symptomatology, including dyskinesia. The goal of clinicians should be to ensure a high SNR in order to maintain or enhance the motor repertoire of patients. To understand why such an approach would be beneficial, we first review mechanisms of dyskinesia, as well as their impact on the quality of life of patients and on the health-care system. Theoretical and practical bases for the SNR approach are then discussed.

SUMMARY

Clinicians should not only consider the level of motor symptomatology when assessing the efficacy of their treatment strategy, but also breadth of the motor repertoire available to patients.

The role of oxidative stress in Parkinson's disease

Oxidative stress plays an important role in the degeneration of dopaminergic neurons in Parkinson's disease (PD). Disruptions in the physiologic maintenance of the redox potential in neurons interfere with several biological processes, ultimately leading to cell death. Evidence has been developed for oxidative and nitrative damage to key cellular components in the PD substantia nigra. A number of sources and mechanisms for the generation of reactive oxygen species (ROS) are recognized including the metabolism of dopamine itself, mitochondrial dysfunction, iron, neuroinflammatory cells, calcium, and aging. PD causing gene products including DJ-1, PINK1, parkin, alpha-synuclein and LRRK2 also impact in complex ways mitochondrial function leading to exacerbation of ROS generation and susceptibility to oxidative stress. Additionally, cellular homeostatic processes including the ubiquitin-proteasome system and mitophagy are impacted by oxidative stress. It is apparent that the interplay between these various mechanisms contributes to neurodegeneration in PD as a feed forward scenario where primary insults lead to oxidative stress, which damages key cellular pathogenetic proteins that in turn cause more ROS production. Animal models of PD have yielded some insights into the molecular pathways of neuronal degeneration and highlighted previously unknown mechanisms by which oxidative stress contributes to PD. However, therapeutic attempts to target the general state of oxidative stress in clinical trials have failed to demonstrate an impact on disease progression. Recent knowledge gained about the specific mechanisms related to PD gene products that modulate ROS production and the response of neurons to stress may provide targeted new approaches towards neuroprotection.

Interaction of D₃ preferring agonist (-)-N⁶-(2-(4-(biphenyl-4-yl)piperazin-1-yl)ethyl)-N⁶-propyl-4,5,6,7-tetrahydrobenzo[d]thiazole-2,6-diamine (D-264) with cloned human D₂L, D₂S, and D₃ receptors: potent stimulation of mitogen-activated protein kinases and G protein-coupled inward rectifier potassium channels

This study aims to determine the effect of the novel D(3) dopamine receptor agonist, D-264, on activation of D(3) and D(2) dopamine receptor signal transduction pathways and cell proliferation. AtT-20 neuroendocrine cells stably expressing human D(2S), D(2L), and D(3) dopamine receptors were treated with D-264 and the coupling of the receptors to mitogen-activated protein kinase (MAPK) and G protein-coupled inward rectifier potassium (GIRK) channels was determined using Western blotting and whole-cell voltage clamp recording, respectively. D-264 potently activated MAPK signaling pathway coupled to D(2S), D(2L), and D(3) dopamine receptors. The activation of MAPK was more pronounced than the reference agonist quinpirole and was longer lasting. D-264 also activated GIRK channels coupled to D(2S), D(2L), and D(3) receptors. In addition, D-264 dose-dependently induced cell proliferation in AtT-D(2L) and AtT-D(3) cells. These results indicate that D-264 robustly activates GIRK channels and MAPK coupled to D(2) and D(3) dopamine receptors in AtT-20 cells. D-264 is also a potent inducer of cell proliferation.

Long-term efficacy and safety of safinamide as add-on therapy in early Parkinson's disease

BACKGROUND AND PURPOSE

Safinamide is an α-aminoamide with both dopaminergic and non-dopaminergic mechanisms of action in Phase III clinical development as a once-daily add-on to dopamine agonist (DA) therapy for early Parkinson's disease (PD).

METHODS

Study 017 was a 12-month, randomized, double-blind, placebo-controlled pre-planned extension study to the previously reported Study 015. Patients received safinamide 100 or 200 mg/day or placebo added to a single DA in early PD. The primary efficacy endpoint was the time from baseline (Study 015 randomization) to 'intervention', defined as increase in DA dose; addition of another DA, levodopa or other PD treatment; or discontinuation due to lack of efficacy. Safinamide groups were pooled for the primary efficacy endpoint analysis; post hoc analyses were performed on each separate dose group.

RESULTS

Of the 269 patients randomized in Study 015, 227 (84%) enrolled in Study 017 and 187/227 (82%) patients completed the extension study. Median time to intervention was 559 and 466 days in the pooled safinamide and placebo groups, respectively (log-rank test; P = 0.3342). In post hoc analyses, patients receiving safinamide 100 mg/day experienced a significantly lower rate of intervention compared with placebo (25% vs. 51%, respectively) and a delay in median time to intervention of 9 days (P < 0.05; 240- to 540-day analysis).

CONCLUSIONS

The pooled data from the safinamide groups failed to reach statistical significance for the primary endpoint of median time from baseline to additional drug intervention. Post hoc analyses indicate that safinamide 100 mg/day may be effective as add-on treatment to DA in PD.

Nonmotor outcomes in Parkinson's disease: is deep brain stimulation better than dopamine replacement therapy?

Nonmotor symptoms are an integral part of Parkinson's disease and cause significant morbidity. Pharmacological therapy helps alleviate the disease but produces nonmotor manifestations. While deep brain stimulation (DBS) has emerged as the treatment of choice for motor dysfunction, the effect on nonmotor symptoms is not well known. Compared with pharmacological therapy, bilateral subthalamic nucleus (STN)-DBS or globus pallidum interna (GPi)-DBS has significant beneficial effects on pain, sleep, gastrointestinal and urological symptoms. STN-DBS is associated with a mild worsening in verbal fluency while GPi-DBS has no effect on cognition. STN-DBS may improve cardiovascular autonomic disturbances by reducing the dose of dopaminergic drugs. Because the motor effects of STN-DBS and GPi-DBS appear to be similar, nonmotor symptoms may determine the target choice in surgery of future patients.

Optimizing levodopa therapy to treat wearing-off symptoms in Parkinson's disease: focus on levodopa/carbidopa/entacapone

Levodopa has been the mainstay of Parkinson's disease (PD) therapy for over 40 years, with its efficacy surpassing that of other antiparkinsonian medications. As such, most PD patients eventually require levodopa-based therapy during the course of the disease. However, despite its proven efficacy, long-term levodopa therapy is associated with motor complications, with wearing-off being the most prevalent. Wearing-off occurs, in part, as a result of the short half-life of levodopa, which leads to fluctuations in plasma levodopa levels. A pharmacokinetic profile characterized by a higher trough value of levodopa can be achieved by combining levodopa/carbidopa with entacapone, which inhibits the peripheral breakdown of levodopa, resulting in higher plasma levodopa levels. Here, we review the limitations of conventional levodopa and the clinical data for levodopa/carbidopa/entacapone in treating patients with wearing-off.

Clinical aspects and management of levodopa-induced dyskinesia

In Parkinson's disease, one of the most troublesome dilemmas is the treatment of levodopa-induced dyskinesia. After a few years, chronic treatment with levodopa is associated with the development of dyskinesias. Strategies to delay or to reduce dyskinesias are based on the change of levodopa dosing or the early use of dopamine agonists. Dopamine agonists with different pharmacological profile are available. Our paper was aimed to analyse the clinical impact and the management of dyskinesias with dopamine agonists.

Continuous dopaminergic stimulation: clinical aspects and experimental bases

In patients with Parkinson disease, pulsatile administration of dopaminergic drugs is associated with motor fluctuations and dyskinesias. By contrast, treatments that provide more continuous dopaminergic stimulation are associated with less intense motor complications. This can be achieved by using drugs with longer half-lives, delayed release formulations, and routes of administration that permit continuous delivery. The mechanisms by which different modes of dopaminergic treatment (pulsatile or continuous) determine the motor response are not fully understood. However, the use of experimental models of parkinsonism has helped understand the motor complications associated with pulsatile dopamine replacement. These studies have provided important insights into the biochemical and molecular changes in the basal ganglia in response to continuous stimulation. In addition, these models have facilitated the development of new treatments that may stabilize the motor response and the biochemical alterations in the basal ganglia to provide more efficient forms of continuous dopaminergic stimulation in patients with Parkinson disease.

Patient considerations in early management of Parkinson's disease: focus on extended-release pramipexole

This article reviews the role of an extended-release formulation of pramipexole in the treatment of Parkinson's disease at an early stage. Pramipexole is a nonergot D(2)/D(3) synthetic aminobenzothiazole derivative that is effective as monotherapy in early disease and as an adjunct to levodopa in patients with motor fluctuations. Although levodopa is the current "gold standard" for treatment of Parkinson's disease, its effectiveness fades rapidly and its use results in serious motor fluctuations (on-off, wearing-off, freezing, involuntary movements) for most patients with the disease. Pramipexole has selective actions at dopamine receptors belonging to the D(2) subfamily, where it possesses full activity similar to dopamine itself. Its preferential affinity for the D(3) receptor subtype could contribute to its efficacy in the treatment of both the motor and psychiatric symptoms of Parkinson's disease. The best approach to medical management of early Parkinson's disease remains controversial. While enormous progress has been made in the treatment of the disease, challenges still remain. A variety of treatment-related and patient-related factors must be taken into account when making these decisions. The current approach to treatment of early Parkinson's disease depends in part on individual patient factors, including age, severity and nature of symptoms and their impact, presence of cognitive dysfunction, possible underlying behavioral factors predisposing to impulse control disorders, and other comorbidities. Today, the once-daily extended-release formulation of pramipexole offers the advantages of easy continuous delivery of drug and convenience to patients, particularly early in the disease when monotherapy is the rule. Thus, a new "levodopa-sparing" paradigm for treating Parkinson's disease may now be possible, whereby patients are initially treated with pramipexole and levodopa is added only as necessary.

Modelling the cost effectiveness of treatments for Parkinson's disease: a methodological review

The objective of this review was to assess models of cost effectiveness for Parkinson's disease (PD) published after July 2002 and to derive recommendations for future modelling. A systematic literature search was performed in the databases PubMed, Current Contents, EMBASE, EconLit, the Cochrane Database of Systematic Reviews, and DARE (Database of Abstracts of Reviews of Effectiveness), NHS EED (Economic Evaluation Database) and HTA (Health Technology Assessment) of the UK NHS Centre for Review and Dissemination (July 2002 to March 2010). Only fully published studies using decision trees, Markov models, individual simulation models or sets of mathematical equations were included. Most of the 11 studies identified used Markov models (n = 9) and two employed were based on decision trees. Based on the Hoehn & Yahr (HY) scale, authors evaluated the cost effectiveness of drug treatments (n = 6), surgical approaches such as deep brain stimulation (n = 1) or striatal cell grafting (n = 1), and diagnostic procedures such as single photon emission computed tomography (SPECT) testing (n = 3) over a time horizon of 1 year to lifetime. Costs were adapted to address a societal and/or healthcare provider/third-party payer perspective. All but one of the interventions investigated were considered cost effective or cost saving. Cost-effectiveness modelling in PD between 2003 and 2010 showed only minor improvement when compared with our earlier review of models published from 1998 up to 2003. Cost-effectiveness modelling recommendations were complied with to only a limited extent, leaving room for quality improvement. More advanced modelling approaches may, so far, be under-represented, but may be used in the future, driven by the research question. Adverse events of treatment, co-morbidities or disease complications are not yet sufficiently included in the models to adequately represent clinical reality.

The clinical spectrum of levodopa-induced motor complications

After more than 40 years of clinical use, levodopa (LD) still remains the gold standard for symptomatic efficacy in Parkinson's disease (PD). However, long-term treatment with LD is often complicated by the development of various types of motor response oscillations as well as drug-induced dyskinesias. These treatment-related motor complications evolve in approximately one-third of patients after only 2 years of LD exposure and, once established, they are difficult to treat and significantly contribute to overall disability and disease burden. Although first described soon after the introduction of LD, the pathophysiology of motor complications is still not completely understood. In fact, it is most likely that non-physiological pulsatile stimulation of dopamine receptors, which is followed by various downstream alterations, plays a key role in the development of LD-induced motor response oscillations and dyskinesias. This review outlines the various types of motor complications and will also address underlying mechanisms, treatment options, as well as impact on clinical disability and quality of life (QoL).

Milestones in Parkinson's disease therapeutics

In the mid-1980s, the treatment of Parkinson's disease was quite exclusively centered on dopatherapy and was focusing on dopamine systems and motor symptoms. A few dopamine agonists and a monoamine oxidase B inhibitor (selegiline) were used as adjuncts in advanced Parkinson's disease. In the early 2010s, levodopa remains the gold standard. New insights into the organization of the basal ganglia paved the way for deep brain stimulation, especially of the subthalamic nucleus, providing spectacular improvement of drug-refractory levodopa-induced motor complications. Novel dopamine agonists (pramipexole, ropinirole, rotigotine), catecholmethyltransferase inhibitors (entacapone), and monoamine oxidase B inhibitors (rasagiline) have also been developed to provide more continuous oral delivery of dopaminergic stimulation in order to improve motor outcomes. Using dopamine agonists early, before levodopa, proved to delay the onset of dyskinesia, although this is achieved at the price of potentially disabling daytime somnolence or impulse control disorders. The demonstration of an antidyskinetic effect of the glutamate antagonist amantadine opened the door for novel nondopaminergic approaches of Parkinson's disease therapy. More recently, nonmotor symptoms (depression, dementia, and psychosis) have been the focus of the first randomized controlled trials in this field. Despite therapeutic advances, Parkinson's disease continues to be a relentlessly progressive disorder leading to severe disability. Neuroprotective interventions able to modify the progression of Parkinson's disease have stood out as a failed therapeutic goal over the last 2 decades, despite potentially encouraging results with compounds like rasagiline. Newer molecular targets, new animal models, novel clinical trial designs, and biomarkers to assess disease modification have created hope for future therapeutic interventions.