Prevalence and Correlates of Anti-Parkinson Drug Use in a Nationally Representative Sample

Anticholinergic drugs for parkinsonism and other movement disorders

Anticholinergic (AC) drugs, a medication class that acts by blocking nicotinic and muscarinic acetylcholine receptors, were first utilized for therapeutic purposes in the mid-19th century. Initial applications were as symptomatic therapy for Parkinson disease (PD), a practice continuing to the present. Initially, the AC drugs used were naturally-occurring plant compounds. Synthetic AC drugs were developed in the late 1940s and predominated in neurological therapeutics. Until the advent of pharmaceuticals acting upon striatal dopaminergic motor pathways, AC drugs provided the only effective means for lessening tremors and other clinical problems of the PD patient. However, because dopaminergic compounds are so effective at meeting the needs of the typical PD patient, AC medications are far less utilized by clinicians today. In recent years, there has been only a few investigations of AC drugs as neurological treatments. This review will revisit the clinical landscape of AC pharmacology and application for movement disorders along with recent research in search of improving therapeutics with AC drugs.

Update: Descriptive epidemiology of Parkinson disease

We review the descriptive epidemiology of Parkinson disease (PD). PD is a prevalent neurologic disorder in high Socio-Demographic Index (SDI) nations with rising prevalence in low and middle SDI nations. PD became a prevalent disorder in high SDI nations during the 20th century. Population growth, population aging, and increased disease duration are major drivers of rising PD prevalence. Exposure to industrial toxicants may also be a contributor to rising PD prevalence. PD is an age-related disorder with incidence likely peaking in the 8th decade of life and prevalence in the 9th decade of life. PD is notable for significant sex difference in PD risk with greater risk in men. There may be ancestral differences in PD prevalence and risk. PD is associated with moderately increased mortality though this may be underestimated. Despite significant research, there is considerable uncertainty about basic features of PD epidemiology.

Dopaminergic treatment strategies for people with Parkinson's disease in Europe: a retrospective analysis of PRISM trial data

BACKGROUND

Levodopa (LD) is the most effective drug to treat Parkinson's disease (PD). The recently concluded multinational Parkinson's Real-World Impact Assessment (PRISM) trial revealed highly variable prescription patterns of LD monotherapy across six European countries. The reasons remain unclear.

METHODS

In this post hoc analysis of PRISM trial data, we used multivariate logistic regression analysis to identify socio-economic factors affecting prescription practice. We applied receiver-operated characteristics and split sample validation to test model accuracy to predict treatment class (LD monotherapy vs. all other treatments).

RESULTS

Subject age, disease duration, and country of residence were significant predictors of treatment class. The chance of receiving LD monotherapy increased by 6.9% per year of age. In contrast, longer disease duration reduced the likelihood of receiving LD monotherapy by 9.7% per year. Compared to the other countries, PD patients in Germany were 67.1% less likely and their counterparts in the UK 86.8% more likely to receive an LD monotherapy. The model classification accuracy of treatment class assignment was 80.1%. The area under the curve to predict treatment condition was 0.758 (95% CI [0.715, 0.802]). Split sample validation revealed poor sensitivity (36.6%), but excellent specificity (92.7%) to predict treatment class.

CONCLUSION

The relative lack of socio-economic variables affecting prescription practice in the study sample and limited model accuracy to predict treatment class suggest the presence of additional, country-specific factors affecting prescription patterns that were not assessed in the PRISM trial. Our findings indicate that physicians still avoid prescribing LD monotherapy to younger PD patients.

Exploring the prescribing trends and factors affecting initial anti-parkinsonian drug selection in Korea: A nationwide population-based cohort study

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder typically treated with dopamine replacement therapy and dopamine agonists (DAs) to alleviate symptoms and minimize dyskinesia. Optimal treatment strategies for patients newly diagnosed with PD have been a topic of debate for many years.

METHODS

We conducted a 10-year descriptive study of drug prescription trends and factors affecting prescription choices for newly diagnosed drug-naïve PD patients using data from the National Health Insurance program in Korea. To identify statistically significant differences in yearly trends, we employed the Cochran-Armitage trend test. Additionally, we utilized multiple logistic regression analysis to investigate the factors associated with the selection of levodopa and DAs as initial anti-parkinsonian drugs.

RESULTS

A total of 99,118 patients with PD who were prescribed levodopa or DAs alone as initial anti-parkinsonian drugs between 2011 and 2020 were eligible for inclusion in the analysis. The prescription rate of DAs increased until 2012, and then steadily decreased annually. The likelihood of levodopa prescription increased with age and at higher-level hospitals. In terms of comorbidities, patients with Alzheimer's disease and cerebrovascular diseases were more likely to be prescribed levodopa than those with peptic ulcer disease and dyslipidemia.

CONCLUSION

The decline in levodopa prescriptions was reversed in 2012, and the prescription rate has continued to increase until recently. The odds ratio of levodopa prescription increased in elderly patients with Alzheimer's disease and decreased in patients with Medical aid insurance and peptic ulcer disease.

Does Black vs. White race affect practitioners' appraisal of Parkinson's disease?

Black patients are diagnosed with Parkinson's disease (PD) at half the rate as White patients. The reasons for this large disparity are unknown. Here, we review evidence that practitioner bias may contribute. A key sign of PD is hypomimia or decreased facial expressivity. However, practitioner bias surrounding facial expressivity in Black people versus White people may lead practitioners to appraise Black patients with hypomimia as having higher levels of facial expressivity. Furthermore, practitioner bias may cause them to characterize reduced facial expressivity as being due to negative personality traits, as opposed to a medical sign, in Black patients with hypomimia. This racial bias in the evaluation of hypomimia in Black versus White patients could profoundly impact subsequent referral decisions and rates of diagnosis of PD. Therefore, exploring these differences is expected to facilitate addressing health care disparities through earlier and more accurate detection of PD in Black patients.

Identifying the Sources of Racial Disparity in the Treatment of Parkinson's Disease With Deep Brain Stimulation

BACKGROUND

Deep brain stimulation (DBS) is a highly efficacious treatment for appropriately selected patients with advanced, medically refractory Parkinson's disease (PD). It is severely underutilized in Black patients-constituting a major treatment gap. The source of this disparity is unknown, but its identification and correction are necessary to provide equitable care.

OBJECTIVE

To identify sources of racial disparity in DBS for PD.

METHODS

We predicted the demographics of potential DBS candidates by synthesizing published data on PD and race. We retrospectively examined the clinical course of a cohort including all patients with PD evaluated for DBS at our center from 2016 to 2020, testing whether the rate of DBS use and time from evaluation to surgery differed by race. We also tested whether the geographic distribution of patient catchment was biased relative to racial demographics.

RESULTS

Far fewer Black patients were evaluated for DBS than would be expected, given regional demographics. There was no significant difference in the rate at which Black patients evaluated in our clinic were treated with DBS, compared with White patients. Fewer patients were recruited from portions of the surrounding area with larger Black populations.

CONCLUSION

The known underuse of DBS in Black patients with PD was replicated in this sample from a center in a racially diverse metropolitan area, but was not attributable to the presurgical workup. Future work should examine the transition from medical management to surgical evaluation where drivers of disparity are potentially situated. Surgical practices should increase outreach to physicians managing PD in underserved areas.

Racial and Ethnic Disparities in Parkinson Disease: A Call to Action

Health disparities are pervasive in the United States. In the field of Parkinson disease (PD), profound racial and ethnic disparities exist in diagnosis, treatment, and research participation, leading to differential health outcomes and lack of generalizable research data. Racial and ethnic disparities not only limit our understanding of this complex heterogeneous disorder but also hamper our ability to provide new evidence-based care for America's most vulnerable populations. In this report, we summarize findings from our comprehensive white paper for the Michael J. Fox Foundation that reviews the current state of knowledge on racial and ethnic disparities in PD care in the following areas: epidemiology, etiology, phenotype and diagnosis, treatment, and research. We also identify knowledge gaps and necessary policy changes to ensure equitable, high-value care for all persons with PD. These strategies are designed to help identify and reduce health disparities among persons with PD and may serve as a model for other neurologic diseases.

Mind the gap: Inequalities in mental health care and lack of social support in Parkinson disease

Inequalities in mental healthcare and lack of social support during the COVID-19 pandemic have lowered quality of life and increased overall burden of disease in people with Parkinson's (PWP). Although the pandemic has brought attention to these inequalities, they are long standing and will persist unless addressed. Lack of awareness of mental health issues is a major barrier and even when recognized disparities based on race, gender, and socioeconomic factors limit access to already scarce resources. Stigma regarding mental illness is highly prevalent and is a major barrier even when adequate care exists. Limited access to mental healthcare during the pandemic and in general increases the burden on caregivers and families. Historically, initiatives to improve mental healthcare for PWP focused on interventions designed for specialty and academic centers generally located in large metropolitan areas, which has created unintended geographic disparities in access. In order to address these issues this point of view suggests a community-based wellness model to extend the reach of mental healthcare resources for PWP.

Antimuscarinic Anticholinergic Medications in Parkinson Disease: To Prescribe or Deprescribe?

The relative importance of antimuscarinic anticholinergic medications for Parkinson's disease (PD) declined after the introduction of levodopa, such that anticholinergic medications are now much more likely to be prescribed for clinical indications other than parkinsonism. Recent studies have found an association between anticholinergic medication exposure and future risk of dementia in older individuals and those with PD. These findings provide a further reason to avoid the use of anticholinergic medications to treat motor symptoms of PD. More importantly, they raise the question of whether one of the goals of PD treatment should be to deprescribe all medications with anticholinergic properties, regardless of their indication, to reduce dementia risk. In this review, we discuss the use of anticholinergic medications in PD, the evidence supporting the association between anticholinergic medications and future dementia risk, and the potential implications of these findings for clinical care in PD.

Parkinson's Disease in African Americans: A Review of the Current Literature

Parkinson’s disease (PD) is the second most common neurodegenerative disease, though evidence suggests that this disorder does not affect all racial groups similarly. Research in African Americans, in particular, has been conflicting. Some studies have found similar prevalence rates in African Americans and whites whereas other studies have found much lower prevalence and incidence rates in African Americans. A few studies identify potential factors underlying these discrepancies, including biologic differences as well as disparities in healthcare access. However, African Americans remain underrepresented in research studies, which make understanding the underlying reasons for these differences difficult. The purpose of this paper is to summarize existing research in African Americans with PD, highlight some of the reasons why differences exist in diagnostic rates of PD in this population, and briefly discuss interventions that may need to be made in order to ensure adequate care is provided to these patients.

COVID-19 social distancing: negative effects on people with Parkinson disease and their associations with confidence for self-management

BACKGROUND

The purpose of this study was to describe the effects of COVID-19 social distancing on the function, health, and well-being of people with Parkinson disease (PD), and test the association of these effects with patients' activation levels, i.e., their skills and confidence in managing their health.

METHODS

Community-dwelling individuals with PD answered an anonymous web-based survey. Part 1 included 27 multiple-choice questions regarding changes in function, health, medical care, and well-being. Part 2 consisted of the Patient Activation Measure, which enquired about skills and confidence in managing one's health.

RESULTS

Respondents (N = 142) reported decreases in various function (24.8%-37.3%), health (33.8%-43%), and well-being (26.1%-47.1%) domains. Rehabilitation ceased for 61.2%. Among those reporting a worsening of health, 67.8% associated this with the cessation of rehabilitative treatments or decrease in physical activity. Patients' activation levels were inversely correlated with increased assistance for activities of daily living, increased tiredness, worsening symptoms, and lack of support from family and friends.

CONCLUSIONS

Social distancing had a major negative impact on the health and function of people with PD.

PRACTICAL IMPLICATIONS

Supporting people with PD skills and confidence in managing health may preserve their physical and mental health during this period of dramatic changes in life's circumstances.

Disparities in diagnosis, treatment and survival between Black and White Parkinson patients

INTRODUCTION

Racial disparities in diagnosis, treatment and survival in Black patients with Parkinson's disease (PD) compared to White patients have not been well studied, largely due to limited number of studies and information on Black patients in healthcare systems. Studying racial disparities and identifying underlying factors in large populations are important to understand PD and improve care.

METHODS

We retrospectively identified PD patients on both races from 1/1/2006 to 10/31/2017 and compared demographics, socioeconomic status (educations, incomes and insurances), comorbidities (all categories, including mood, cognition and psychosis), treatment (medications for parkinsonism and major non-motor symptoms, and frequency and locations of healthcare) and survival, and identified factors associated with medication usage and survival.

RESULTS

We retrospectively studied 2033 PD patients, of whom 725 were Black. Black patients lacked male predominance, were 4 years older at first diagnosis here, more likely to smoke and live in a low education and income community, and possessed limited insurances compared to White patients. Black patients also had more comorbidities and were more likely to receive care through emergency or inpatient service, but less likely to be on medications for parkinsonism and mood disorders. Race, age, smoking status, insurance type, frequency and locations of healthcare and comorbidities were associated with medication usage. Black race, older age, inpatient admission and malignancy were associated with increased risk of death.

CONCLUSION

We revealed racial disparities in diagnosis, treatment and survival, and factors associated with medication usage and survival in the largest reported Black PD cohort from a single center.

Ethnic Variation in the Manifestation of Parkinson's Disease: A Narrative Review

The global prevalence of Parkinson's disease is increasing, yet the characteristics, risk factors and genetics of PD in Black, Asian and Hispanic populations is little understood. In this paper we review the published literature on clinical variation in the symptoms and signs of Parkinson's disease in different ethnic groups and responses to treatment. We included any study that sampled patients with Parkinson's disease from distinct ethnic backgrounds. We conclude that whilst there is little published evidence for ethnic variation in the clinical features of Parkinson's disease, there are substantial limitations and gaps in the current literature, which mean that the evidence does necessarily not fit with clinical observation. Possible explanations for expected differences in manifestation include genetic determinants, the co-existence of cerebrovascular disease and/or Alzheimer's disease pathology, healthcare inequalities and socio-cultural factors.

Low Sustainment of High-Dose Oral Medication Regimens for Advanced Parkinson's Disease in Medicare Beneficiaries

BACKGROUND

Increasing doses of oral antiparkinson medications are indicated in advanced Parkinson's disease (PD), but little is known about sustainment of high-dose regimens.

OBJECTIVE

To investigate sustainment of high-dose oral medication regimens in Medicare beneficiaries with incident advanced PD.

METHODS

This retrospective cohort study utilized 100%fee-for-service Medicare claims from 2011-2013. We identified advanced PD using a pharmacy claims-based proxy and selected patients who initiated a new high-dose oral medication regimen (daily levodopa equivalent dose [LED] >1000 mg/day for ≥30 days) in 2012. In the following 12 months, we examined: 1) annual proportion of days covered (PDC)≥0.80 and 2) presence of a ≥ 90 day continuous gap at varying dosage thresholds: the initial >1000 mg/day, >800 mg/day, >500 mg/day, or >0 mg/day.

RESULTS

We identified 9,405 patients with advanced PD (mean age 77.4 [SD 6.8] years; 53%men). Only 5%maintained a regimen of >1000 mg/day at PDC ≥0.80; 75% had a ≥ 90-day gap in that dosage level. At a dosage threshold of >800 mg/day, 20% had a PDC ≥0.80 and 53% had a ≥ 90-day gap; at >500 mg/day, 56% had a PDC ≥0.80 and 19%had a ≥ 90-day gap; and at >0 mg/day (any dose), 76% had a PDC ≥0.80 and only 10%had a≥90-day gap.

CONCLUSION

Few patients with advanced PD sustained a high-dose oral medication regimen in the year following initiation, but most sustained a substantially lower-dose regimen. Strategies to improve advanced PD treatment are needed.

Burden of Parkinson's Disease by Severity: Health Care Costs in the U.S. Medicare Population

BACKGROUND

Current understanding of the health care costs of Parkinson's disease (PD) and the incremental burden of advanced disease is incomplete.

OBJECTIVES

The aim of this study was to assess the direct economic burden associated with advanced versus mild/moderate PD in a prevalent national sample of elderly U.S. Medicare beneficiaries with a PD diagnosis.

METHODS

Analyzing 100% fee-for-service Medicare claims from 2013, we defined advanced PD with a medication-based algorithm and calculated all-cause and PD-related costs for the overall sample and by disease severity. We measured primary PD-related costs (based on claims with a primary diagnosis of PD) and any PD-related costs (based on claims with PD in any diagnostic field). Generalized linear models were used to estimate risk-adjusted mean cost differences between the advanced and mild/moderate PD groups for the calendar year.

RESULTS

The final sample (N = 144,703) had mean observed all-cause, primary PD-related, and any PD-related costs of $23,041 (SD, $34,045), $3429 (SD, $7431), and $9924 (SD, $22,140), respectively. Twenty percent of patients were classified as advanced PD. Costs varied substantially; any PD-related mean costs were $483 for the lowest patient decile (which included 1% of the advanced group) and $48,145 for the highest decile (which included 15% of the advanced group). Incremental risk-adjusted costs of advanced PD were $5818 (95% confidence interval [CI]: $5411-$6225) for all-cause costs, $3644 (95% CI: $3484-$3806) for primary PD-related costs, and $6088 (95% CI: $5779-$6398) for any PD-related costs.

CONCLUSIONS

Elderly Medicare beneficiaries with PD had substantial variation in PD-related costs. Advanced PD was associated with a larger economic burden than mild/moderate PD. © 2020 International Parkinson and Movement Disorder Society.

Prescription pattern of anti-Parkinson's disease drugs in Japan based on a nationwide medical claims database

Introduction

Parkinson's disease (PD) treatment should follow guidelines and be tailored to each patient. Large database analyses can provide insights into prescribing patterns.

Methods

Retrospective, cross-sectional study of patients (≥30 years) with PD diagnosis (ICD-10; schizophrenia/cerebrovascular disease excluded) using health insurance claims data (April 2008-December 2016) from the Japan Medical Data Vision database. Prescription patterns of anti-PD drugs were analysed by patient age and sex, calendar year, and overall.

Results

The analysis comprised 155,493 PD patient-years (56.1% women, mean 73.4 years). Patient number increased each year, mainly because of database expansion. L-dopa as monotherapy was the most common prescription (22.7% of patient-years); non-ergot dopamine agonists (DAs) were also common (7.6% as monotherapy, 6.8% with L-dopa). Monotherapy was prescribed for ~50% of patient-years, two drugs for 14.1%, and at least three drugs for 18.4%. Consistent with Japanese guidelines, L-dopa was mostly prescribed to older patients (≥60 years), whereas non-ergot DAs were mostly prescribed to middle-aged patients (peak at 50-69 years). Between 2008 and 2011, L-dopa prescription decreased while that of non-ergot DAs increased; this pattern reversed between 2012 and 2016.

Conclusion

These results indicate that Japanese clinicians are adhering to Japanese guidelines and tailoring anti-PD treatment to individual patients.

Adherence to treatment guideline recommendations for Parkinson's disease in Japan: A longitudinal analysis of a nationwide medical claims database between 2008 and 2016

Background

Adherence to the 2011 Japanese guidelines for treatment of Parkinson’s disease (PD) in real-life practice is unknown.

Methods

In this retrospective longitudinal observational study, we examined patterns and trends in anti-PD drug prescriptions in 20,936 patients (≥30 years of age with newly diagnosed PD [International Classification of Diseases–Tenth code G20 or PD Hoehn and Yahr scale 1–5] and one or more prescriptions) using nationwide registry data between 2008 and 2016. Data are presented as descriptive statistics.

Results

Half (49.6%) of the patients received levodopa (L-dopa) monotherapy, followed by non-ergot dopamine agonists (DA) prescribed as monotherapy (8.3%) or with L-dopa (8.1%). Consistent with the guidelines, 75% of patients were prescribed within 13 days of initial diagnosis; L-dopa monotherapy was the most prescribed drug in patients ≥70 years of age, whereas non-ergot DA monotherapy was more likely to be prescribed than L-dopa in patients between 30 and 50 years of age. Inconsistent with the guidelines, L-dopa monotherapy was the most prescribed drug in patients between 51 and 69 years of age. Over the course of 4 years of treatment, the prescription rate of L-dopa monotherapy and non-ergot DA monotherapy decreased by 63.7% and 44.1%, respectively, whereas that of L-dopa and non-ergot DA combination therapy increased by 103.7%. Combination therapy with L-dopa, non-ergot DA, and monoamine oxidase-B inhibitors was gradually increased at a later stage.

Conclusion

These results highlight that the state of PD treatment in Japan adheres to most of the recommendations in the 2011 national guidelines, but also precedes the 2018 guidelines.

Use of a medication-based algorithm to identify advanced Parkinson's disease in administrative claims data: Associations with claims-based indicators of disease severity

Introduction

Lack of a gold standard definition for advanced Parkinson's Disease (APD), coupled with absence of disease severity information in diagnostic codes, hinders use of large administrative databases for conducting population health and comparative effectiveness studies.

Methods

Using pharmacy claims data, we created an algorithm to identify APD: any 30-day average levodopa equivalent dose (LED) >1000 mg/day. Using 2013 100% U.S. Medicare claims, we applied this algorithm and used multivariate logistic regression to examine associations between assigned APD status and claims-based indicators of PD severity (any deep brain stimulation, fall, hallucinations, walker, wheelchair, specialty bed, dementia diagnosis, skilled nursing facility, hospice), adjusting for sociodemographic, clinical, and treatment characteristics. Levodopa >1000 mg/day, levodopa >800 mg/day and LED >800 mg/day were used in sensitivity analysis.

Results

In our sample (N = 144,703), 20% were assigned APD status based on the LED >1000 mg/day cut-off. This group had significantly higher odds of having each claims-based indicator, compared with those assigned mild-moderate PD status. Odds ratios were highest for indicators for any DBS (OR: 2.96; 95% CI:2.75–3.19) and specialty bed (OR:2.15, 95% CI: 1.99–2.32) and lowest for fall (OR:1.27; 95% CI:1.20–1.34) and dementia diagnosis (OR:1.21; 95% CI:1.18–1.25). Results based on alternative approaches were similar.

Conclusions

Medicare patients classified as having APD via a pharmacy claims-based algorithm had higher odds of having claims-based clinical markers of APD, compared with patients categorized as having mild-moderate PD. This proxy strategy could facilitate future claims-based studies and warrants further refinement and validation using medical records or other clinical sources.

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Prescription claims can be used to calculate average daily levodopa-equivalent dose.

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An algorithm (LED >1000 mg/day) was used to identify advanced Parkinson's in claims.

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20% of people with Parkinson's disease in a Medicare sample aged 65+ met this definition.

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The remaining 80% of the sample was classified as having mild/moderate disease.

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The advanced group had higher odds of having clinical markers of advanced disease.

The characteristics and treatment patterns of patients with Parkinson's disease in the United States and United Kingdom: A retrospective cohort study

Objectives

The objective of the study was to describe treatment patterns in patients newly diagnosed with Parkinson’s disease (PD) in the United States (US) and the United Kingdom (UK).

Methods

This retrospective cohort study used the US IBM MarketScan database (2012–2017) and the UK Clinical Practice Research Datalink (CPRD) (2004–2015) database to describe treatment patterns in incident PD cases. Patients fulfilling the case definition of PD, ≥30 years, with a 2-year baseline period prior to the index date (date of PD diagnosis), and ≥90 days of follow-up were included in the study. Treatment was classified as monotherapy (one PD medication for ≥60 continuous days), polytherapy (at least two PD medications concurrently for ≥60 days), or untreated (no PD medication prescription). Treatment patterns described included type of medication, duration and outcome of treatment.

Results

There were 11,280 patients in IBM MarketScan and 7775 patients in CPRD who fulfilled the study criteria. The proportion of treated patients was 62.4% (US) and 78.6% (UK). The majority of patients were prescribed monotherapy as first-line treatment (US: 85.2%, UK: 68.5%). Levodopa was the most frequently prescribed first-line medication (US: 70.1%, UK: 29.0%). There were 57.9% in the US and 23.8% in the UK who remained on the first monotherapy treatment till the end of the study.

Conclusion

The study has highlighted the current treatment practices in the US and UK, and underscored differences in the two regions impacted by treatment policies and guidelines.

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 2^nd 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.

Metal Chelation Therapy and Parkinson's Disease: A Critical Review on the Thermodynamics of Complex Formation between Relevant Metal Ions and Promising or Established Drugs

The present review reports a list of approximately 800 compounds which have been used, tested or proposed for Parkinson’s disease (PD) therapy in the year range 2014–2019 (April): name(s), chemical structure and references are given. Among these compounds, approximately 250 have possible or established metal-chelating properties towards Cu(II), Cu(I), Fe(III), Fe(II), Mn(II), and Zn(II), which are considered to be involved in metal dyshomeostasis during PD. Speciation information regarding the complexes formed by these ions and the 250 compounds has been collected or, if not experimentally available, has been estimated from similar molecules. Stoichiometries and stability constants of the complexes have been reported; values of the cologarithm of the concentration of free metal ion at equilibrium (pM), and of the dissociation constant K_d (both computed at pH = 7.4 and at total metal and ligand concentrations of 10⁻⁶ and 10⁻⁵ mol/L, respectively), charge and stoichiometry of the most abundant metal–ligand complexes existing at physiological conditions, have been obtained. A rigorous definition of the reported amounts is given, the possible usefulness of this data is described, and the need to characterize the metal–ligand speciation of PD drugs is underlined.