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

Changes in neurologists' treatment preferences for Parkinson's disease in the Netherlands

•Data about treatment preferences for Parkinson's disease (PD) are scarce.•A survey was sent to neurologists in the Netherlands in 2010 and 2021.•In 2021, levodopa was increasingly prescribed for PD.•In 2021, levodopa was increasingly prescribed for younger PD patients.•In 2021, Deep Brain Stimulation became the treatment choice for advanced PD.

Drug Permeability: From the Blood-Brain Barrier to the Peripheral Nerve Barriers

Drug delivery into the peripheral nerves and nerve roots has important implications for effective local anesthesia and treatment of peripheral neuropathies and chronic neuropathic pain. Similar to drugs that need to cross the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) to gain access to the central nervous system (CNS), drugs must cross the peripheral nerve barriers (PNB), formed by the perineurium and blood-nerve barrier (BNB) to modulate peripheral axons. Despite significant progress made to develop effective strategies to enhance BBB permeability in therapeutic drug design, efforts to enhance drug permeability and retention in peripheral nerves and nerve roots are relatively understudied. Guided by knowledge describing structural, molecular and functional similarities between restrictive neural barriers in the CNS and peripheral nervous system (PNS), we hypothesize that certain CNS drug delivery strategies are adaptable for peripheral nerve drug delivery. In this review, we describe the molecular, structural and functional similarities and differences between the BBB and PNB, summarize and compare existing CNS and peripheral nerve drug delivery strategies, and discuss the potential application of selected CNS delivery strategies to improve efficacious drug entry for peripheral nerve disorders.

Dopamine agonist monotherapy utilization in patients with Parkinson's disease

Objectives

To characterize patients with Parkinson's disease (PD) who initiated dopamine agonist (DA) monotherapy, describe medication utilization and provider types, and estimate medication adherence and discontinuation rates.

Methods

Retrospective study identified patients with PD in the Optum Research Database and included those with ≥1 claim for DA or levodopa between 09/01/2012 and 12/31/2018, ≥2 PD diagnoses, commercial or Medicare Advantage Part D (MAPD) insurance, ≥40 years old, and continuous medical and pharmacy coverage ≥12 months before and after index date. A subset of patients receiving DA monotherapy was selected for this analysis. Variables were analyzed descriptively. Adherence was measured with medication possession ratio (MPR) and proportion of days covered (PDC); defined as ≥0.80.

Results

Patients (N = 642) had mean (SD) age of 70.2 (9.9) years, 70.6 % had MAPD coverage, and 61.7 % were male. Neurologists prescribed 64.6 % of DA monotherapy, and 56.9 % of patients had ≥2 PD diagnoses before or on the index date. Index therapy was discontinued by 44.1 % of patients, and 55.9 % persisted for 12 months without change. Mean (SD) time to discontinuation was 102 (79) days. Mean (SD) MPR for patients (n = 562) with ≥2 fills was 0.84 (0.2); 70.3 % were MPR adherent. Mean (SD) PDC for all 642 patients was 0.66 (0.3); 50.5 % were PDC adherent.

Conclusion

Adherence and continuation of therapy were suboptimal, which could translate into poor patient outcomes. Future studies could provide insights on the impact of low adherence and persistence with DA monotherapy.

Treatment initiation for parkinson’s disease in Australia 2013–2018: a nation-wide study

Background

Guidelines highlight the importance of an individualized approach to treatment initiation for Parkinson’s disease. Our aim was to investigate initiation of anti-Parkinson medication in Australia from 2013–2018, and to determine factors predicting choice of initial treatment.

Methods

Cohort of new-users (N = 4,887) of anti-Parkinson medication aged ≥ 40 years were identified from a 10% random representative sample of national medication dispensing data from July-2013 to June-2018. Changes in treatment initiation were examined across the whole cohort and stratified by age and sex.

Results

Treatment initiation was most frequent with levodopa followed by non-ergot dopamine agonists (DAs) and anticholinergics. Two thirds initiated with levodopa across the study period. Initiation with non-ergot DAs increased from 22 to 27% (rate ratio, RR 1.23, 95% confidence interval, CI 1.02–1.47) and initiation with anticholinergics decreased from 6.9% to 2.4% (RR 0.34, 95% CI 0.21–0.55) from 2013–2018. Among persons aged ≥ 65 years, one third of women and one fourth of men initiated on levodopa. Among women aged < 65 years, rates of treatment initiation with DAs (37%) and levodopa (37%) were similar in 2013/2014 but initiation with DA exceeded levodopa thereafter. Among men aged < 65 years, treatment initiation with levodopa (44%-49%) remained more frequent than initiation with DAs (29%-32%) throughout the study period.

Conclusions

Treatment initiation with levodopa was most frequent among persons aged ≥ 65 years, consistent with current guidelines. Whilst the value of levodopa sparing strategies is unclear, treatment initiation with DA has become increasingly common relative to levodopa among women but not among men aged < 65 years.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-03095-3.

Difference in rural and urban Medicare prescription pattern for Parkinson’s disease in Hawai‘i

Background

Medical management of Parkinson’s Disease (PD) is becoming complex. Increasing evidence suggests that patients have better outcomes when they are managed by neurologists. However, access to neurologists can be limited in rural areas. Analysis of prescription pattern can provide insight into access gap rural patients face.

Methods

This retrospective observational study used National Medicare Provider Utilization and Payment Data: Part D Prescriber Public Use Files from 2013 to 2018. Query was made for levodopa, dopamine agonists and other antiparkinsonian medications. The data elements obtained included drug name, number of prescribers, prescriber specialty, number of claims, number of standardized 30-day Part D prescriptions, and number of Medicare beneficiaries in the state of Hawai‘i. Individual prescribing providers were categorized as urban or rural based on their cities of practice. Prescription patterns of urban and rural providers in Hawai‘i as well as difference in provider specialty were compared, using standardized 30-day prescriptions as the primary measure of utilization.

Results

Practice patterns differed between rural and urban areas. In rural Hawai‘i, Rytary, Rotigoitne and selegiline were rarely prescribed. Levodopa percentage was higher in urban Hawai‘i. In urban Hawai‘i, 74.4% of the prescriptions were provided by movement disorders and general neurologists. In rural Hawai'i, 25.1% of the prescriptions were written by neurologists and 74.9% by general practitioners.

Conclusions

In the state of Hawai‘i, there is an urban–rural access gap to neurologists as evidenced by Medicare prescription pattern. Further study is needed to understand the reasons for rural–urban differences in prescription patterns and their impact on outcomes.

An assessment of Parkinson's disease medication treatment patterns in the Medicaid population

INTRODUCTION

Most Parkinson's disease (PD) medication adherence studies have focused on patients with commercial or Medicare health insurance coverage. However, less is known regarding medication treatment patterns within the Medicaid population.

METHODS

This retrospective cohort study utilized 2011-2019 administrative healthcare claims from 7 state Medicaid programs. We compared newly diagnosed patients with PD started on either levodopa or a dopamine agonist (DA). Baseline comorbidities were compared. Outcomes were assessed during a 12-month post-index observation period, and included total medication days, proportion of days covered (PDC), adherence status, persistence to initiating PD medication, and time to non-persistence of initiating PD medication.

RESULTS

Our study sample of 805 Medicaid patients had an average age of 54.1 years, with 52.0% being female. Levodopa was the predominant PD medication at initiation (75.4%). Roughly half of patients had a baseline depressive disorder and nearly 40% had an anxiety disorder. Levodopa patients had a significantly higher PDC compared to DA patients (0.621 vs. 0.546, p = 0.007). An adjusted logistic regression model showed no significant difference in the number of adherent patients between the two groups (p = 0.058). An adjusted Cox proportional hazards model controlling for demographic and baseline variables showed a 26% lower risk of non-persistence for levodopa patients versus DA patients (HR 0.740, CI 0.597-0.917, p = 0.006).

CONCLUSIONS

Adherence and persistence rates were suboptimal following initiation of either levodopa or DA medication for patients with PD in Medicaid programs, though rates were better for those initiated on levodopa.

The role of neuroimaging in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that affects millions of people worldwide. Two hallmarks of PD are the accumulation of alpha-synuclein and the loss of dopaminergic neurons in the brain. There is no cure for PD, and all existing treatments focus on alleviating the symptoms. PD diagnosis is also based on the symptoms, such as abnormalities of movement, mood, and cognition observed in the patients. Molecular imaging methods such as magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT), and positron emission tomography (PET) can detect objective alterations in the neurochemical machinery of the brain and help diagnose and study neurodegenerative diseases. This review addresses the application of functional MRI, PET, and SPECT in PD patients. We provide an overview of the imaging targets, discuss the rationale behind target selection, the agents (tracers) with which the imaging can be performed, and the main findings regarding each target's state in PD. Molecular imaging has proven itself effective in supporting clinical diagnosis of PD and has helped reveal that PD is a heterogeneous disorder, which has important implications for the development of future therapies. However, the application of molecular imaging for early diagnosis of PD or for differentiation between PD and atypical parkinsonisms has remained challenging. The final section of the review is dedicated to new imaging targets with which one can detect the PD-related pathological changes upstream from dopaminergic degeneration. The foremost of those targets is alpha-synuclein. We discuss the progress of tracer development achieved so far and challenges on the path toward alpha-synuclein imaging in humans.

Neuroprotective Effect of Low-Intensity Pulsed Ultrasound on the Mouse MPTP/MPP+ Model of Dopaminergic Neuron Injury

Ultrasound mediated neuromodulation has been demonstrated to a safe treatment strategy in the field of neuroscience. In this study, low-intensity pulsed ultrasound (LIPUS) was used to treat Parkinson's disease (PD) models induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium (MPP⁺) to explore the possibility of ultrasound neuroprotective effect on PD. The results demonstrated that LIPUS treatment can attenuate the central neurotoxicity of MPTP in mice, reduce the loss of tyrosine hydroxylase positive neurons in the substantia nigra pars compacta and decrease the apoptosis in the section of substantia nigra. The movement and balance dysfunctions in PD mice were improved with LIPUS treatment. In addition, we demonstrated that LIPUS can inhibit the decreased activity and increased apoptosis of dopaminergic neurons induced by MPP⁺, restrain the accumulation of reactive oxygen species (ROS) and decrease of mitochondrial membrane potential caused by MPP⁺. Moreover, LIPUS stimulation alone did not cause any cytotoxicity and tissue damage in our study. Taken together, the protective and regulatory effects of LIPUS on dopaminergic neurons make it possible as a new, safe and noninvasive treatment for PD.

Factors affecting the choice of first-line therapy in Parkinson's disease patients in Wales: A population-based study

First line treatment for Parkinson’s disease (PD) is typically either L-dopa or a non-ergot dopamine agonist (DA). However, the options for the treatment of motor symptoms in PD patients have increased in the last thirty years, which have seen several new classes of PD medications introduced onto the market. The purpose of this study is to examine the changes in first line therapy of newly diagnosed Parkinson’s patients between 2000 and 2016 in Wales.

A population-based study evaluated data from the Secure Anonymised Information Linkage (SAIL) Databank of residents in Wales, aged 40 years or older, newly treated with PD medications between 2000 and 2016. The data was compared across three intervals: 2000–2005, 2006–2011 and 2012–2016. Patients were classified by age at diagnosis into young: 40–60 years; mid, 61–80 years; and older >80 years. Logistic regression was undertaken to determine the predictors of PD medication prescribing.

For the whole study period, the profiles of 9142 newly diagnosed PD patients were analysed. L-dopa was the most common first line therapy (80.6%), followed by non-ergot DAs (12.9%) and monoamine oxidase B (MAO-B) inhibitors (7.9%). Odds of L-dopa prescribing were greater in patients >80 years (OR = 20.46 95%CI: 16.25–25.76) and in the period 2012–2016 (OR = 1.98 95% CI: 1.70–2.29). Prescribing of non-ergot DAs significantly declined in 2012–2016 (OR = 0.42 95% CI: 0.35–0.49). Additional factors influencing first line therapy were deprivation, presence of diabetes and prior use of antidepressants. For example, PD patients residing in the least deprived area were less likely to be prescribed L-dopa compared to patients residing in the most deprived area (OR = 0.77 95% CI: 0.65–0.93).

First line therapy in PD in Wales has undergone a significant switch towards L-dopa over the last 16 years. The data indicates reasonable compliance with guidelines on efficacy and safety issues related to Parkinson’s medications.

Autophagy and Redox Homeostasis in Parkinson's: A Crucial Balancing Act

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated primarily from endogenous biochemical reactions in mitochondria, endoplasmic reticulum (ER), and peroxisomes. Typically, ROS/RNS correlate with oxidative damage and cell death; however, free radicals are also crucial for normal cellular functions, including supporting neuronal homeostasis. ROS/RNS levels influence and are influenced by antioxidant systems, including the catabolic autophagy pathways. Autophagy is an intracellular lysosomal degradation process by which invasive, damaged, or redundant cytoplasmic components, including microorganisms and defunct organelles, are removed to maintain cellular homeostasis. This process is particularly important in neurons that are required to cope with prolonged and sustained operational stress. Consequently, autophagy is a primary line of protection against neurodegenerative diseases. Parkinson's is caused by the loss of midbrain dopaminergic neurons (mDANs), resulting in progressive disruption of the nigrostriatal pathway, leading to motor, behavioural, and cognitive impairments. Mitochondrial dysfunction, with associated increases in oxidative stress, and declining proteostasis control, are key contributors during mDAN demise in Parkinson's. In this review, we analyse the crosstalk between autophagy and redoxtasis, including the molecular mechanisms involved and the detrimental effect of an imbalance in the pathogenesis of Parkinson's.

Real-world safety and effectiveness of rotigotine in patients with Parkinson's disease: analysis of a post-marketing surveillance study in Japan

OBJECTIVE

The aim of this study was to evaluate the safety and effectiveness of rotigotine under daily clinical practice in Parkinson's disease patients.

METHODS

The study was a prospective, non-interventional, observational study targeting patients who were treated with rotigotine for the first time, with a 1-year follow-up period from September 2013 to August 2016.

RESULTS

There were 603 patients in the safety population and 599 patients in the effectiveness population. The mean age was 71.6 years, and the age group of ≥65 and ≥80 years accounted for 80% and 18.6% of all patients, respectively. The frequency of adverse drug reaction (ADR) was 34.3%, and common ADRs were application site reaction (20.2%), typical for transdermal patches. However, the majority of patients recovered or was recovering from these ADRs and were non-serious. Although ADRs related to non-motor symptoms of Parkinson's disease were observed, most of them were non-serious. Total scores of the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) (ON-time) significantly decreased from baseline in the effectiveness population. In the analysis of overall improvement in 12 months of post-treatment, ≥70% of patients achieved mild or greater improvement. The safety profiles and improvements in the UPDRS-III score were similar in both the ≥80 years of age group and younger age group.

CONCLUSION

There were no new or notable safety concerns observed, and the effectiveness of rotigotine was suggested in daily clinical practice.

Map kinase signaling as therapeutic target for neurodegeneration

Aging is known to be one of the major risk factors in many neurodegenerative diseases (ND) whose prevalence is estimated to rise in the coming years due to the increase in life expectancy. Examples of neurodegenerative diseases include Huntington's, Parkinson's, and Alzheimer's diseases, along with Amyotrophic Lateral Sclerosis, Spinocerebellar ataxias and Frontotemporal Dementia. Given that so far these ND do not have effective pharmacological therapies, a better understanding of the molecular and cellular mechanisms can contribute to development of effective treatments. During the previous decade, the data indicated that dysregulation of MAP kinases [which included c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1 and 2 (ERK1/2), and p38] are associated with several stages of the inflammatory process which in turn contributes to age-related neurodegenerative diseases. This evidence suggests that control of inflammation through regulation of MAP kinase could be a worthwhile approach against neurodegenerative diseases. In this review we summarize the pathways of MAP kinase signal transduction and different pharmacological inhibitors that can be used in its modulation against ND.

Efficacy of pramipexole combined with levodopa for Parkinson's disease treatment and their effects on QOL and serum TNF- levels

PURPOSE

To investigate the efficacy of combining the dopamine receptor agonist pramipexole with levodopa for Parkinson's disease (PD) treatment and to measure their effects on quality of life and tumor necrosis factor (TNF)-α levels in PD patients.

BASIC PROCEDURE

In total, 160 PD patients who were admitted to our hospital were equally randomized into a control treatment group (levodopa alone) and the study group (pramipexole combined with levodopa). Both groups were treated for 12 weeks.

FINDINGS

After treatment, scores from the Unified Parkinson's Disease Rating Scales (1-3), the Hamilton Depression Scale, and the Parkinson's Disease Questionnaire (PDQ-39) were significantly decreased in both groups, whereas Mini-Mental State Examination scores were significantly increased. After treatment, the study group had significantly lower scores for all scales except the Mini-Mental State Examination, for which those who received combined treatment had significantly higher scores than the control group. The incidence of adverse reactions was significantly lower in the study group than in the control group. Furthermore, after treatment, serum TNF-α levels were significantly decreased in both groups compared with pre-treatment levels.

CONCLUSION

Pramipexole combined with levodopa relieved PD symptoms and improved the quality of life of PD patients, potentially by suppressing serum TNF-α levels.

Lipid-based nanodelivery approaches for dopamine-replacement therapies in Parkinson's disease: From preclinical to translational studies

The incidence of Parkinson's disease (PD), the second most common neurodegenerative disorder, has increased exponentially as the global population continues to age. Although the etiological factors contributing to PD remain uncertain, its average incidence rate is reported to be 1% of the global population older than 60 years. PD is primarily characterized by the progressive loss of dopaminergic (DAergic) neurons and/or associated neuronal networks and the subsequent depletion of dopamine (DA) levels in the brain. Thus, DA or levodopa (l-dopa), a precursor of DA, represent cardinal targets for both idiopathic and symptomatic PD therapeutics. While several therapeutic strategies have been investigated over the past decade for their abilities to curb the progression of PD, an effective cure for PD is currently unavailable. Even DA replacement therapy, an effective PD therapeutic strategy that provides an exogenous supply of DA or l-dopa, has been hindered by severe challenges, such as a poor capacity to bypass the blood-brain barrier and inadequate bioavailability. Nevertheless, with recent advances in nanotechnology, several drug delivery systems have been developed to bypass the barriers associated with central nervous system therapeutics. In here, we sought to describe the adapted lipid-based nanodrug delivery systems used in the field of PD therapeutics and their recent advances, with a particular focus placed on DA replacement therapies. This work initially explores the background of PD; offers descriptions of the most recent molecular targets; currently available clinical medications/limitations; an overview of several lipid-based PD nanotherapeutics, functionalized nanoparticles, and technical aspects in brain delivery; and, finally, presents future perspectives to enhance the use of nanotherapeutics in PD treatment.

Systematic Evaluation of Levodopa Effect on Visual Improvement in Amblyopia: A Meta-analysis

PURPOSE

This study aims to evaluate the effectiveness of levodopa as a therapeutic drug in the treatment of children and adults with amblyopia.

METHODS

We performed a systematic review and meta-analysis with randomized controlled trials of levodopa and placebo in the treatment of amblyopia. All data were identified and extracted from the PubMed, EMBASE, Cochrane libraries, and the Chinese knowledge resource integration database.

RESULTS

After screening the literature and evaluating the quality, 11 studies met the criteria from 308 studies. The mean difference of LogMAR visual acuity between levodopa and the placebo group was -0.1031 (95% confidence interval, -0.11 to -0.09; P < 0.0001). The improvement of visual acuities of the subgroup of younger patients with amblyopia was significantly higher than that of the placebo group (P < 0.0001). Increasing the dosage of levodopa and prolonging the treatment can significantly improve the curative effect.

CONCLUSIONS

Levodopa is effective in the treatment of amblyopia by prolonging the treatment, especially for young patients.

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.

Predictors of motor complications in early Parkinson's disease: A prospective cohort study

OBJECTIVE

The objective of this study was to identify clinical predictors of motor complications (dyskinesia and motor fluctuations) of levodopa in a prospectively recruited PD cohort using longitudinal analysis.

METHODS

An inception cohort (Oxford Discovery) of 734 patients was followed to a maximum of 10 years from diagnosis using a discrete-time survival analysis. A subset analysis was used to validate an online dyskinesia-risk calculator developed from the results of the Stalevo Reduction in Dyskinesia Evaluation PD trial.

RESULTS

A total of 186 cases of dyskinesia and 254 cases of motor fluctuations were observed. Dyskinesia incidence increased with time (risk per 100 participants [95% confidence interval] 13 [11-16] <3.5 years, 16 [13-21] 3.5-5.0 years, 19 [14-26] 5-6.5 years, and 23 [16-33] >6.5 years from diagnosis). Motor complication predictors were grouped as medication predictors, disease predictors and patient predictors. Baseline nonmotor feature severity, low mood, anxiety, and age at symptom onset were associated with motor complications among a number of previously identified predictors. Replication of the Stalevo Reduction in Dyskinesia Evaluation PD calculator was reasonable with the area under the curve for dyskinesia risk score as a predictor of dyskinesia being 0.68 (95% confidence interval, 0.55-0.81).

CONCLUSIONS

This study quantifies risk of motor complications, finds consistent predictors, and demonstrates the novel finding that nonmotor features of PD, particularly low mood and anxiety, are significant risk factors for motor complications. Further validation of dyskinesia risk scores are required as well as evidence to determine if the routine use of such scores can be clinically valuable in enhancing patient care and quality of life. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

A Computational Model of Loss of Dopaminergic Cells in Parkinson's Disease Due to Glutamate-Induced Excitotoxicity

Parkinson's disease (PD) is a neurodegenerative disease associated with progressive and inexorable loss of dopaminergic cells in Substantia Nigra pars compacta (SNc). Although many mechanisms have been suggested, a decisive root cause of this cell loss is unknown. A couple of the proposed mechanisms, however, show potential for the development of a novel line of PD therapeutics. One of these mechanisms is the peculiar metabolic vulnerability of SNc cells compared to other dopaminergic clusters; the other is the SubThalamic Nucleus (STN)-induced excitotoxicity in SNc. To investigate the latter hypothesis computationally, we developed a spiking neuron network-model of SNc-STN-GPe system. In the model, prolonged stimulation of SNc cells by an overactive STN leads to an increase in ‘stress' variable; when the stress in a SNc neuron exceeds a stress threshold, the neuron dies. The model shows that the interaction between SNc and STN involves a positive-feedback due to which, an initial loss of SNc cells that crosses a threshold causes a runaway-effect, leading to an inexorable loss of SNc cells, strongly resembling the process of neurodegeneration. The model further suggests a link between the two aforementioned mechanisms of SNc cell loss. Our simulation results show that the excitotoxic cause of SNc cell loss might initiate by weak-excitotoxicity mediated by energy deficit, followed by strong-excitotoxicity, mediated by a disinhibited STN. A variety of conventional therapies were simulated to test their efficacy in slowing down SNc cell loss. Among them, glutamate inhibition, dopamine restoration, subthalamotomy and deep brain stimulation showed superior neuroprotective-effects in the proposed model.

Therapeutic strategies in the early stages of Parkinson's disease: a cross-sectional evaluation of 15 years' experience with a large cohort of Romanian patients

INTRODUCTION

In patients older than 70 years there is no valid alternative to progressively introduced substitution therapy. The antiparkinsonian drugs introduced in the last decade to treat Parkinson's disease, especially in its early phases, promised a comparable efficacy in reducing symptoms to levodopa. In younger patients and/or patients with mild symptoms we hoped to delay the motor complications by postponing the start of levodopa therapy. While these assumptions may not be true for all patients, probably the most important current challenge is the optimal starting moment of levodopa therapy. The aim of the study was to analyze the therapeutical choices during the early phase of Parkinson's disease in the Neurological Departments of Târgu Mures¸ County Hospital.

MATERIALS AND METHODS

We examined data obtained from hospitalized Parkinson's disease patients during a 15-year period. According to the duration of the disease we split the patients into two groups, patients with Parkinson's disease for less than or equal to 5 years and patients with disease duration longer than 5 years, and then analyzed only the former group.

RESULTS

During the examined period, 2,379 patients with Parkinson's disease were hospitalized, and 1,237 patients had a disease duration shorter than 5 years. In this group, 18 patients had monoamine oxidase inhibitor monotherapy. Also, 665 patients received dopamine agonists, in 120 cases as monotherapy and in 83 patients associated with monoamine oxidase inhibitors. In 521 patients we found only levodopa treatment. A further 481 patients received combined therapy (levodopa with dopamine agonists and/or monoamine oxidase inhibitors).

CONCLUSION

Treatment strategies for the early stages of Parkinson's disease in our group were comparable to results from other studies. However, the authors feel that neurologists should use levodopa-sparing drugs with greater courage. Furthermore, if the clinical context is appropriate, physicians should combine substitution therapy with other antiparkinsonian drugs in order to reduce levodopa doses.

A noninterventional study evaluating the effectiveness of rotigotine and levodopa combination therapy in younger versus older patients with Parkinson's disease

BACKGROUND

PD0013 was a 6-month noninterventional study in clinical practice comparing effectiveness/tolerability of rotigotine+levodopa in younger (<70 years) vs. older (≥70 years) Parkinson's disease (PD) patients.

METHODS

Patients previously received levodopa for ≥6 months as monotherapy/in combination with another dopamine-agonist (DA). Primary variable: Unified PD Rating Scale (UPDRS) Part-II change from baseline to end-of-observation-period (EOP).

RESULTS

91 younger/99 older patients started rotigotine; 68 younger/62 older patients completed the study. Most switched from levodopa+another DA. Addition of rotigotine as first DA was more common in older patients (20.2% vs.15.4%). Mean ± SD rotigotine-exposure: 6.1 ± 3.4 mg/24h younger vs. 4.9 ± 2.4 mg/24h older. Eleven patients changed levodopa dose. At EOP, improvement in mean UPDRS-II was greater in younger patients (p = 0.0289). UPDRS-II responder-rate (≥20% decrease in UPDRS-II score) was higher in younger patients (42.3% vs. 25.9%). Improvement across age groups was similar on PD Sleep Scale-2 and Clinical Global Impressions-Improvement Scale. Adverse drug reactions (ADRs), and discontinuations because of ADRs, were more common among older patients. There were no new safety signals.

CONCLUSIONS

Despite low rotigotine doses, when added to levodopa/switched from levodopa+another DA, rotigotine led to greater improvement in UPDRS-II in younger patients (<70 years). Individual patient data revealed clinically meaningful improvements in UPDRS-II in both groups.

The dopaminergic system dynamic in the time perception: a review of the evidence

Dopaminergic system plays a key role in perception, which is an important executive function of the brain. Modulation in dopaminergic system forms an important biochemical underpinning of neural mechanisms of time perception in a very wide range, from milliseconds to seconds to longer daily rhythms. Distinct types of temporal experience are poorly understood, and the relationship between processing of different intervals by the brain has received little attention. A comprehensive understanding of interval timing functions should be sought within a wider context of temporal processing, involving genetic aspects, pharmacological models, cognitive aspects, motor control and the neurological diseases with impaired dopaminergic system. Particularly, an unexplored question is whether the role of dopamine in interval timing can be integrated with the role of dopamine in non-interval timing temporal components. In this review, we explore a wider perspective of dopaminergic system, involving genetic polymorphisms, pharmacological models, executive functions and neurological diseases on the time perception. We conclude that the dopaminergic system has great participation in impact on time perception and neurobiological basis of the executive functions and neurological diseases.