Pharmacokinetic optimisation in the treatment of Parkinson's disease : an update

Pharmacomicrobiomics: a new field contributing to optimizing drug therapy in Parkinson's disease

Gut microbiota, which act as a determinant of pharmacokinetics, have long been overlooked. In recent years, a growing body of evidence indicates that the gut microbiota influence drug metabolism and efficacy. Conversely, drugs also exert a substantial influence on the function and composition of the gut microbiota. Pharmacomicrobiomics, an emerging field focusing on the interplay of drugs and gut microbiota, provides a potential foundation for making certain advances in personalized medicine. Understanding the communication between gut microbiota and antiparkinsonian drugs is critical for precise treatment of Parkinson's disease. Here, we provide a historical overview of the interplay between gut microbiota and antiparkinsonian drugs. Moreover, we discuss potential mechanistic insights into the complex associations between gut microbiota and drug metabolism. In addition, we also draw attention to microbiota-based biomarkers for predicting antiparkinsonian drug efficacy and examine current state-of-the-art knowledge of microbiota-based strategies to optimize drug therapy in Parkinson's disease.

Non-invasive, continuous oral delivery of solid levodopa-carbidopa for management of Parkinson's disease

When short plasma half-life drugs act only briefly, they require frequent or continuous administration. We report the engineering of a non-invasive oral drug delivery system for long-term, continuous administration of these drugs. Their non-invasive, long-term, continuous administration at daily doses exceeding 100 mg has, for many years, been considered an insurmountable challenge. We show that over 1200 mg/day of 4:1 levodopa-carbidopa (LD-CD) can be non-invasively and continuously extruded when formulated as a semisolid paste, loaded with 63%w/w of the solid drugs. The drug delivery system comprises a reusable orthodontic retainer with a co-molded pocket into which the patient inserts after each meal a new 1 mL propellant-driven, prefilled, disposable, drug delivery extruder. The paste is delivered to the lingual side of the teeth where it is mixed with saliva and swallowed. As reported elsewhere, a 15-day, 16 patient open label clinical trial of the drug delivery system continuously extruding LD-CD paste significantly reduces the variability of the plasma LD concentration and alleviates symptoms of advanced Parkinson's disease (PD) as compared to LD-CD tablets.

Tricompartmental Microcarriers with Controlled Release for Efficient Management of Parkinson's Disease

Parkinson's is a progressive neurodegenerative disease of the nervous system. It has no cure, but its symptoms can be managed by supplying dopamine artificially to the brain.This work aims to engineer tricompartmental polymeric microcarriers by electrohydrodynamic cojetting technique to encapsulate three PD (Parkinson's disease) drugs incorporated with high encapsulation efficiency (∼100%) in a single carrier at a fixed drug ratio of 4:1:8 (Levodopa (LD): Carbidopa(CD): Entacapone (ENT)). Upon oral administration, the drug ratio needs to be maintained during subsequent release from microparticles to enhance the bioavailability of primary drug LD. This presents a notable challenge, as the three drugs vary in their aqueous solubility (LD > CD > ENT). The equilibrium of therapeutic release was achieved using a combination of FDA-approved polymers (PLA, PLGA, PCL, and PEG) and the disc shape of particles. In vitro studies demonstrated the simultaneous release of all the three therapeutics in a sustained and controlled manner. Additionally, pharmacodynamics and pharmacokinetics studies in Parkinson's disease rats induced by rotenone showed a remarkable improvement in PD conditions for the microparticles-fed rats, thereby showing a great promise toward efficient management of PD.

Dopamine Modulates Effective Connectivity in Frontal Cortex

There is increasing evidence that the left lateral frontal cortex is hierarchically organized such that higher-order regions have an asymmetric top-down influence over lower order regions. However, questions remain about the underlying neuroarchitecture of this hierarchical control organization. Within the frontal cortex, dopamine plays an important role in cognitive control functions, and we hypothesized that dopamine may preferentially influence top-down connections within the lateral frontal hierarchy. Using a randomized, double-blind, within-subject design, we analyzed resting-state fMRI data of 66 healthy young participants who were scanned once each after administration of bromocriptine (a dopamine agonist with preferential affinity for D2 receptor), tolcapone (an inhibitor of catechol-O-methyltransferase), and placebo, to determine whether dopaminergic stimulation modulated effective functional connectivity between hierarchically organized frontal regions in the left hemisphere. We found that dopaminergic drugs modulated connections from the caudal middle frontal gyrus and the inferior frontal sulcus to both rostral and caudal frontal areas. In dorsal frontal regions, effectivity connectivity strength was increased, whereas in ventral frontal regions, effective connectivity strength was decreased. These findings suggest that connections within frontal cortex are differentially modulated by dopamine, which may bias the influence that frontal regions exert over each other.

Dopaminergic regulation of inflammation and immunity in Parkinson's disease: friend or foe?

Parkinson's disease (PD) is a neurodegenerative disease affecting 7-10 million people worldwide. Currently, there is no treatment available to prevent or delay PD progression, partially due to the limited understanding of the pathological events which lead to the death of dopaminergic neurons in the substantia nigra in the brain, which is known to be the cause of PD symptoms. The current available treatments aim at compensating dopamine (DA) deficiency in the brain using its precursor levodopa, dopaminergic agonists and some indirect dopaminergic agents. The immune system is emerging as a critical player in PD. Therefore, immune-based approaches have recently been proposed to be used as potential antiparkinsonian agents. It has been well-known that dopaminergic pathways play a significant role in regulating immune responses in the brain. Although dopaminergic agents are the primary antiparkinsonian treatments, their immune regulatory effect has yet to be fully understood. The present review summarises the current available evidence of the immune regulatory effects of DA and its mimics and discusses dopaminergic agents as antiparkinsonian drugs. Based on the current understanding of their involvement in the regulation of neuroinflammation in PD, we propose that targeting immune pathways involved in PD pathology could offer a better treatment outcome for PD patients.

Levodopa-Induced Dyskinesias in Parkinson's Disease: An Overview on Pathophysiology, Clinical Manifestations, Therapy Management Strategies and Future Directions

Since its first introduction, levodopa has become the cornerstone for the treatment of Parkinson's disease and remains the leading therapeutic choice for motor control therapy so far. Unfortunately, the subsequent appearance of abnormal involuntary movements, known as dyskinesias, is a frequent drawback. Despite the deep knowledge of this complication, in terms of clinical phenomenology and the temporal relationship during a levodopa regimen, less is clear about the pathophysiological mechanisms underpinning it. As the disease progresses, specific oscillatory activities of both motor cortical and basal ganglia neurons and variation in levodopa metabolism, in terms of the dopamine receptor stimulation pattern and turnover rate, underlie dyskinesia onset. This review aims to provide a global overview on levodopa-induced dyskinesias, focusing on pathophysiology, clinical manifestations, therapy management strategies and future directions.

Clinical benefit of MAO-B and COMT inhibition in Parkinson's disease: practical considerations

Inhibitors of monoamine oxidase B (MAO-B) and catechol-O-methyltransferase (COMT) are major strategies to reduce levodopa degradation and thus to increase and prolong its effect in striatal dopaminergic neurotransmission in Parkinson's disease patients. While selegiline/rasagiline and tolcapone/entacapone have been available on the market for more than one decade, safinamide and opicapone have been approved in 2015 and 2016, respectively. Meanwhile, comprehensive data from several post-authorization studies have described the use and specific characteristics of the individual substances in clinical practice under real-life conditions. Here, we summarize current knowledge on both medication classes, with a focus on the added clinical value in Parkinson's disease. Furthermore, we outline practical considerations in the treatment of motor fluctuations and provide an outlook on ongoing studies with MAO-B and COMT inhibitors.

Management of Motor Symptoms for Patients with Advanced Parkinson's Disease without Safe Oral Access: A Scoping Review

Context: Parkinson's disease (PD) is the second most common neurodegenerative disorder worldwide. Oral medications for control of motor symptoms are the mainstay of treatment. However, as the disease progresses, patients with PD may develop dysphagia that prohibits them from safely taking oral medications. Currently there are no clinical guidelines for managing distressing motor symptoms in patients with PD and severe dysphagia, which can therefore be quite challenging. Objectives: To provide an exhaustive summary of current literature on pharmacological interventions for patients with PD who do not have safe oral access in managing distressing motor symptoms. Indication, route, doses, frequency, outcome, and adverse effects will be discussed. Methods: A scoping review using Medline, Embase, CENTRAL, CINAHL, AgeLine, and PsycINFO databases (1946-2021) was conducted. Articles examining patients with PD and dysphagia who are eligible to receive palliative care or at end of life were included. Studies that included patients who were also on oral PD medications or received device-aided therapy were excluded from this review. Results: A total of 3821 articles were screened for title and abstract, 259 were selected for full-text review, and 20 articles were selected for data extraction. These included five case reports, one retrospective cohort study, one book chapter, and 13 narrative reviews. There are very few articles addressing the issue of treatment of patients with advanced PD who are unable to take oral medications. Although rotigotine patch and apormorphine injections are most frequently recommended, there are no clinical trials in this patient population to support those recommendations. Conclusion: This study highlights a need for further research examining the efficacy and dosing of nonoral medications in advanced PD with dysphagia.

Quality Control Dissolution Data Is Biopredictive for a Modified Release Ropinirole Formulation: Virtual Experiment with the Use of Re-Developed and Verified PBPK Model

Physiologically based pharmacokinetic and absorption modeling are being used by industry and regulatory bodies to address various scientifically challenging questions. While there is high confidence in the prediction of exposure for the BCS class I drugs administered as immediate-release formulations, in the case of prolonged-release formulations, special attention should be given to the input dissolution data. Our goal was to develop and verify a PBPK model for a BCS class I compound, ropinirole, and check the biopredictiveness of the dissolution data for the prolonged-release formulation administered by Parkinson’s patients. The model was built based on quality control dissolution data reported in the certificates of analysis and verified with the use of data derived from five clinical trial reports. The simulated pharmacokinetic parameters being within a two-fold range of the observed values confirmed acceptable model performance, in vivo relevance of the in vitro dissolution profiles, and indirectly indicated ropinirole stable release from the formulation in the patients’ gastro-intestinal tract. Ropinirole PBPK model will be used for exploring potential clinical scenarios while developing a new formulation.

Mechanisms of peripheral levodopa resistance in Parkinson's disease

Parkinson’s disease (PD) is an increasingly common neurodegenerative condition. The disease has a significant negative impact on quality of life, but a personalized management approach can help reduce disability. Pharmacotherapy with levodopa remains the cornerstone of treatment, and a gratifying and sustained response to this treatment is a supportive criterion that argues in favor of an underlying diagnosis of PD. Yet, in daily practice, it is not uncommon to encounter patients who appear to have true PD, but who nevertheless seem to lose the responsiveness to levodopa (secondary non-responders). Some patients may even fail to respond altogether (primary non-responders). Here, we address how two mechanisms of “peripheral resistance” may underlie this failing response to levodopa in persons with PD. The first explanation relates to impaired bowel motility leading to secondary bacterial overgrowth, and more specifically, to the excessive bacterial production of the enzyme tyrosine decarboxylase (TDC). This enzyme may convert levodopa to dopamine in the gut, thereby hampering entry into the circulation and, subsequently, into the brain. The second explanation relates to the systemic induction of the enzyme aromatic l-amino acid decarboxylase (AADC), leading to premature conversion of levodopa into dopamine, again limiting the bioavailability within the brain. We discuss these two mechanisms and focus on the clinical implications, potential treatments and directions for future research.

Pharmacokinetics of Levodopa and 3-O-Methyldopa in Parkinsonian Patients Treated with Levodopa and Ropinirole and in Patients with Motor Complications

Parkinson’s disease (PD) is a progressive, neurodegenerative disorder primarily affecting dopaminergic neuronal systems, with impaired motor function as a consequence. The most effective treatment for PD remains the administration of oral levodopa (LD). Long-term LD treatment is frequently associated with motor fluctuations and dyskinesias, which exert a serious impact on a patient’s quality of life. The aim of our study was to determine the pharmacokinetics of LD: used as monotherapy or in combination with ropinirole, in patients with advanced PD. Furthermore, an effect of ropinirole on the pharmacokinetics of 3-OMD (a major LD metabolite) was assessed. We also investigated the correlation between the pharmacokinetic parameters of LD and 3-OMD and the occurrence of motor complications. Twenty-seven patients with idiopathic PD participated in the study. Thirteen patients received both LD and ropinirole, and fourteen administered LD monotherapy. Among 27 patients, twelve experienced fluctuations and/or dyskinesias, whereas fifteen were free of motor complications. Inter- and intra-individual variation in the LD and 3-OMD concentrations were observed. There were no significant differences in the LD and 3-OMD concentrations between the patients treated with a combined therapy of LD and ropinirole, and LD monotherapy. There were no significant differences in the LD concentrations in patients with and without motor complications; however, plasma 3-OMD levels were significantly higher in patients with motor complications. A linear one-compartment pharmacokinetic model with the first-order absorption was adopted for LD and 3-OMD. Only mean exit (residence) time for 3-OMD was significantly shorter in patients treated with ropinirole. Lag time, V/F, CL/F and t_max of LD had significantly lower values in patients with motor complications. On the other hand, AUC were significantly higher in these patients, both for LD and 3-OMD. 3-OMD C_max was significantly higher in patients with motor complications as well. Our results showed that ropinirole does not influence LD or 3-OMD concentrations. Higher 3-OMD levels play a role in inducing motor complications during long-term levodopa therapy.

Prediction of motor Unified Parkinson's Disease Rating Scale scores in patients with Parkinson's disease using surface electromyography

OBJECTIVE

Parkinson's disease (PD) is a chronic neurodegenerative disorder with increasing prevalence in the elderly. Especially patients with advanced PD often require complex medication regimens due to fluctuations, that is abrupt transitions from ON to OFF or vice versa. Current gold standard to quantify PD-patients' motor symptoms is the assessment of the Unified Parkinson's Disease Rating Scale (UPDRS), which, however, is cumbersome and may depend upon investigators. This work aimed at developing a mobile, objective and unobtrusive measurement of motor symptoms in PD.

METHODS

Data from 45 PD-patients was recorded using surface electromyography (sEMG) electrodes attached to a wristband. The motor paradigm consisted of a tapping task performed with and without dopaminergic medication. Our aim was to predict UPDRS scores from the sEMG characteristics with distinct regression models and machine learning techniques.

RESULTS

A random forest regression model outnumbered other regression models resulting in a correlation of 0.739 between true and predicted UPDRS values.

CONCLUSIONS

PD-patients' motor affection can be extrapolated from sEMG data during a simple tapping task. In the future, such records could help determine the need for medication changes in telemedicine applications.

SIGNIFICANCE

Our findings support the utility of wearables to detect Parkinson's symptoms and could help in developing tailored therapies in the future.

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.

Stimuli-responsive In situ gelling system for nose-to-brain drug delivery

The diagnosis and treatment of neurological ailments always remain an utmost challenge for research fraternity due to the presence of BBB. The intranasal route appeared as an attractive and alternative route for brain targeting of therapeutics without the intrusion of BBB and GI exposure. This route directly and effectively delivers the therapeutics to different regions of the brain via olfactory and trigeminal nerve pathways. However, shorter drug retention time and mucociliary clearance curtail the efficiency of the intranasal route. The in situ mucoadhesive gel overthrow the limitations of direct nose-to-brain delivery by not only enhancing nasal residence time but also minimizing the mucociliary clearance and enzymatic degradation. This delivery system further improves the nasal absorption as well as bioavailability of drugs in the brain. The in situ mucoadhesive gel is a controlled and sustained release system that facilitates the absorption of various proteins, peptides and other larger lipophilic and hydrophilic moieties. Owing to multiple benefits, in situ gelling system has been widely explored to target the brain via nasal route. However, very few review works are reported which explains the application of in situ nasal gel for brain delivery of CNS acting moieties. Hence, in this piece of work, we have initially discussed the global statistics of neurological disorders reported by WHO and other reputed organizations, nasal anatomy, mechanism and challenges of nose-to-brain drug delivery. The work mainly focused on the use of different stimuli-responsive polymers, specifically thermoresponsive, pH-responsive, and ion triggered systems for the development of an effective and controlled dosage form, i.e., in situ nasal gel for brain targeting of bioactives. We have also highlighted the origin, structure, nature and phase transition behavior of the smart polymers found suitable for nasal administration, including poloxamer, chitosan, EHEC, xyloglucan, Carbopol, gellan gum and DGG along with their application in the treatment of neurological disorders. The article is aimed to gather all the information of the past 10 years related to the development and application of stimuli-responsive in situ nasal gel for brain drug delivery.

Wearable Electrochemical Sensors for the Monitoring and Screening of Drugs

Wearable electrochemical sensors capable of noninvasive monitoring of chemical markers represent a rapidly emerging digital-health technology. Recent advances toward wearable continuous glucose monitoring (CGM) systems have ignited tremendous interest in expanding such sensor technology to other important fields. This article reviews for the first time wearable electrochemical sensors for monitoring therapeutic drugs and drugs of abuse. This rapidly emerging class of drug-sensing wearable devices addresses the growing demand for personalized medicine, toward improved therapeutic outcomes while minimizing the side effects of drugs and the related medical expenses. Continuous, noninvasive monitoring of therapeutic drugs within bodily fluids empowers clinicians and patients to correlate the pharmacokinetic properties with optimal outcomes by realizing patient-specific dose regulation and tracking dynamic changes in pharmacokinetics behavior while assuring the medication adherence of patients. Furthermore, wearable electrochemical drug monitoring devices can also serve as powerful screening tools in the hands of law enforcement agents to combat drug trafficking and support on-site forensic investigations. The review covers various wearable form factors developed for noninvasive monitoring of therapeutic drugs in different body fluids and toward on-site screening of drugs of abuse. The future prospects of such wearable drug monitoring devices are presented with the ultimate goals of introducing accurate real-time drug monitoring protocols and autonomous closed-loop platforms toward precise dose regulation and optimal therapeutic outcomes. Finally, current unmet challenges and existing gaps are discussed for motivating future technological innovations regarding personalized therapy. The current pace of developments and the tremendous market opportunities for such wearable drug monitoring platforms are expected to drive intense future research and commercialization efforts.

Biopharmaceutical Potential of Selegiline Loaded Chitosan Nanoparticles in the Management of Parkinson's Disease

BACKGROUND

Selegiline hydrochloride, a hydrophilic anti-Parkinson' moiety, undergoes extensive first-pass metabolism and has low bioavailability. A process to obtain of selegiline (SH) loaded chitosan nanoparticles was attempted to circumvent the above problem, through intranasal delivery.

METHODS

SH loaded polymeric nanoparticles were prepared by ionic gelation of chitosan with tripolyphosphate, and stabilized by tween 80/ poloxamer 188. The resulting nanoparticles (NPs) were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, entrapment efficiency, particle size, zeta potential and surface morphology by scanning electron microscopy. Further, they were schematically evaluated for mucoadhesive strength, in-vitro drug release, release kinetics, pharmacokinetics, catalepsy, akinesia, in-vivo lipid peroxidation, nitrite levels, glutathione, catalase enzyme levels in brain and physicochemical stability parameters.

RESULTS

Selegiline nanoparticles (SP18) produced were in size of 63.1 nm, polydispersity index of 0.201, zeta potential of +35.2 mV, mucoadhesion of 65.4% and entrapment efficiency of 74.77%. Selegiline showed biphasic release from nanoparticles, over a period of 36 h, with Fickian diffusion controlled release profile. Maximum concentration of SH in plasma was recognized as 52.71 ng/ml at 2 h for SP18, 20.09 ng/ml at 1 h for marketed formulation, and 21.69 ng/ ml for drug solution. SH loaded NPs showed a reversive effect in catalepsy and akinesia behaviour. This effect was especially pronounced in rats receiving SH loaded CS-NPs. Significant decrease in lipid peroxidation and nitrite concentration; increase in reduced glutathione and catalase enzyme levels were obtained due to antioxidant characteristics of SH, which turned to be useful to treat Parkinson's disease.

CONCLUSION

Selegiline loaded chitosan nanoparticles form an effective non-invasive drug delivery system of direct nose to brain targeting in Parkinson's disease.

Dopamine and Risky Decision-Making in Gambling Disorder

Gambling disorder is a behavioral addiction associated with impairments in value-based decision-making and cognitive control. These functions are thought to be regulated by dopamine within fronto-striatal circuits, but the role of altered dopamine neurotransmission in the etiology of gambling disorder remains controversial. Preliminary evidence suggests that increasing frontal dopamine tone might improve cognitive functioning in gambling disorder. We therefore examined whether increasing frontal dopamine tone via a single dose of the catechol-O-methyltransferase (COMT) inhibitor tolcapone would reduce risky choice in human gamblers (n = 14) in a randomized double-blind placebo-controlled crossover study. Data were analyzed using hierarchical Bayesian parameter estimation and a combined risky choice drift diffusion model (DDM). Model comparison revealed a nonlinear mapping from value differences to trial-wise drift rates, confirming recent findings. An increase in risk-taking under tolcapone versus placebo was about five times more likely, given the data, than a decrease [Bayes factor (BF) = 0.2]. Examination of drug effects on diffusion model parameters revealed that an increase in the value dependency of the drift rate under tolcapone was about thirteen times more likely than a decrease (BF = 0.073). In contrast, a reduction in the maximum drift rate under tolcapone was about seven times more likely than an increase (BF = 7.51). Results add to previous work on COMT inhibitors in behavioral addictions and to mounting evidence for the applicability of diffusion models in value-based decision-making. Future work should focus on individual genetic, clinical and cognitive factors that might account for heterogeneity in the effects of COMT inhibition.

From OFF to ON—Treating OFF Episodes in Parkinson’s Disease

In Parkinson’s disease (PD), OFF episodes continue to present a serious burden for patients, and their effective management remains a substantial unmet clinical need. Understanding of the pathophysiology of OFF episodes has advanced in recent years, providing valuable insights for improved treatments. OFF episodes generally appear 3–5 years after starting levodopa treatment, but can begin much earlier. They are characterized by motor symptoms (including tremor, rigidity, slowness, incoordination, and weakness) and are almost always associated with some non-motor symptoms (including psychological symptoms, pain, urinary problems, swallowing difficulties, and shortness of breath). In PD, higher doses of levodopa are associated with increased risk of motor and non-motor complications, which are notable limitations for longterm therapy. Their occurrence is associated with intermittent levodopa delivery and consequent fluctuating plasma levels. These issues can be offset using lower levodopa doses where possible, incremental dose increases, and combinations of levodopa with other pharmacological agents. OFF episodes in PD can be caused by gastroparesis and/or by Helicobacter pylori infection, which delays delivery of levodopa. These issues can be addressed using new formulations for continuous intrajejunal administration. In addition, pen injector, intranasal, and inhaled dosing systems have been studied and may provide relief via non-intestinal routes. Other approaches include deep-brain stimulation, which is effective but is restricted by costs and potential adverse events. This report presents the highlights of a satellite symposium held at the 14th International Conference on Alzheimer’s & Parkinson’s Diseases (AD/PD™ 2019), Lisbon, Portugal, which discussed the nature of OFF episodes in PD, associated risk factors and the potential of current and future treatments to effectively manage them and increase ON time.

Current Therapeutic Strategies and Perspectives for Neuroprotection in Parkinson's Disease

Parkinson's disease is a progressive neurodegenerative disorder of dopaminergic striatal neurons in basal ganglia. Treatment of Parkinson's disease (PD) through dopamine replacement strategies may provide improvement in early stages and this treatment response is related to dopaminergic neuronal mass which decreases in advanced stages. This treatment failure was revealed by many studies and levodopa treatment became ineffective or toxic in chronic stages of PD. Early diagnosis and neuroprotective agents may be a suitable approach for the treatment of PD. The essentials required for early diagnosis are biomarkers. Characterising the striatal neurons, understanding the status of dopaminergic pathways in different PD stages may reveal the effects of the drugs used in the treatment. This review updates on characterisation of striatal neurons, electrophysiology of dopaminergic pathways in PD, biomarkers of PD, approaches for success of neuroprotective agents in clinical trials. The literature was collected from the articles in database of PubMed, MedLine and other available literature resources.

Pharmacokinetics and tolerability of inhaled levodopa from a new dry-powder inhaler in patients with Parkinson's disease

Background

Inhaled levodopa may quickly resolve off periods in Parkinson's disease. Our aim was to determine the pharmacokinetics and tolerability of a new levodopa dry-powder inhaler.

Methods

A single-centre, single-ascending, single-dose-response study was performed. Over three visits, eight Parkinson's disease patients (not in the 'off state') received by inhalation 30 mg or 60 mg levodopa, or their regular oral levodopa. Maximum levodopa plasma concentration (C _max), time to maximum plasma concentration (T_max) and area under the concentration time curve 0-180 min were determined. Spirometry was performed three times at each visit.

Results

After inhalation, levodopa T _max occurred within 15 min in all participants, whereas after oral administration, T _max ranged from 20 min to 90 min. The bioavailability of inhaled levodopa without carboxylase inhibitor was 53% relative to oral levodopa with carboxylase inhibitor. No change in lung-function parameters was observed and none of the patients experienced cough or dyspnoea. No correlation was observed between inhalation parameters and levodopa pharmacokinetic parameters.

Conclusion

Inhaled levodopa is well tolerated, absorbed faster than oral levodopa, and can be robustly administered over a range of inhalation flow profiles. It therefore appears suitable for the treatment of off periods in Parkinson's disease.

Hypotension and bradycardia, a serious adverse effect of piribedil, a case report and literature review

Background

Dopamine agonists (DAs) are efficacious for the treatment of motor and nonmotor symptoms in patients with Parkinson’s disease (PD). The treatment of PD with DAs is often complicated by adverse drug reactions (ADRs) of dopaminergic and non-dopaminergic origins. The DA piribedil is widely used in Asian, European, and Latin American countries; therefore, its ADRs are pertinent to clinicians. Here we present a rare case of hypotension and bradycardia that is significantly related to the dosage of piribedil.

Case presentation

A middle-aged male, diagnosed with PD, received dopamine replacement with piribedil. When taking 50 mg piribedil daily dose, the patient didn’t feel any discomfort. Two hours after taking 100 mg piribedil he presented with serious concomitant hypotension and bradycardia with a blood pressure (BP) reading of 85/48 mmHg and a heart rate (HR) of 45 beats/min when sitting. After taking 75 mg piribedil, the patient showed the same symptoms with BP reading at 70/45 mmHg and HR of 47 beats/min in the same position. Upon replacing treatment with pramipexole 0.125 mg, 0.25 mg, and 0.375 mg three times a day, no further cardiovascular effects persisted.

Conclusions

No studies have previously reported the simultaneous observation of position-unrelated hypotension and bradycardia after taking small doses of piribedil. More studies are needed to explore the effects of DAs on BP and HR, especially piribedil. Piribedil is efficacious for the treatment of PD, but it is important to weigh the potential risk of hypotension and bradycardia against the clinical benefits of this drug.

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.

Effects of tolcapone and bromocriptine on cognitive stability and flexibility

RATIONALE

The prefrontal cortex (PFC) and basal ganglia (BG) have been associated with cognitive stability and cognitive flexibility, respectively. We hypothesized that increasing PFC dopamine tone by administering tolcapone (a catechol-O-methyltransferase (COMT) inhibitor) to human subjects should promote stability; conversely, increasing BG dopamine tone by administering bromocriptine (a D2 receptor agonist) should promote flexibility.

OBJECTIVE

We assessed these hypotheses by administering tolcapone, bromocriptine, and a placebo to healthy subjects who performed a saccadic eye movement task requiring stability and flexibility.

METHODS

We used a randomized, double-blind, within-subject design that was counterbalanced across drug administration sessions. In each session, subjects were cued to prepare for a pro-saccade (look towards a visual stimulus) or anti-saccade (look away) on every trial. On 60% of the trials, subjects were instructed to switch the response already in preparation. We hypothesized that flexibility would be required on switch trials, whereas stability would be required on non-switch trials. The primary measure of performance was efficiency (the percentage correct divided by reaction time for each trial type).

RESULTS

Subjects were significantly less efficient across all trial types under tolcapone, and there were no significant effects of bromocriptine. After grouping subjects based on Val158Met COMT polymorphism, we found that Met/Met and Val/Met subjects (greater PFC dopamine) were less efficient compared to Val/Val subjects.

CONCLUSIONS

Optimal behavior was based on obeying the environmental stimuli, and we found reduced efficiency with greater PFC dopamine tone. We suggest that greater PFC dopamine interfered with the ability to flexibly follow the environment.

Levodopa in Parkinson's Disease: Current Status and Future Developments

BACKGROUND

Ever since the pioneering reports in the 60s, L-3,4-Dioxyphenylalanine (levodopa) has represented the gold standard for the treatment of Parkinson's Disease (PD). However, long-term levodopa (LD) treatment is frequently associated with fluctuations in motor response with serious impact on patient quality of life. The pharmacokinetic and pharmacodynamic properties of LD are pivotal to such motor fluctuations: discontinuous drug delivery, short half-life, poor bioavailability, and narrow therapeutic window are all crucial for such fluctuations. During the last 60 years, several attempts have been made to improve LD treatment and avoid long-term complications.

METHODS

Research and trials to improve the LD pharmacokinetic since 1960s are reviewed, summarizing the progressive improvements of LD treatment.

RESULTS

Inhibitors of peripheral amino acid decarboxylase (AADC) have been introduced to achieve proper LD concentration in the central nervous system reducing systemic adverse events. Inhibitors of catechol-O-methyltransferase (COMT) increased LD half-life and bioavailability. Efforts are still being made to achieve a continuous dopaminergic stimulation, with the combination of oral LD with an AADC inhibitor and a COMT inhibitor, or the intra-duodenal water-based LD/ carbidopa gel. Further approaches to enhance LD efficacy are focused on new non-oral administration routes, including nasal, intra-duodenal, intrapulmonary (CVT-301) and subcutaneous (ND0612), as well as on novel ER formulations, including IPX066, which recently concluded phase III trial.

CONCLUSION

New LD formulations, oral compounds as well as routes have been tested in the last years, with two main targets: achieve continuous dopaminergic stimulation and find an instant deliver route for LD.

Placement of the AbbVie PEG-J tube for the treatment of Parkinson's disease in the interventional radiology suite

The primary treatment for Parkinson's disease is dopaminergic stimulation. Although levodopa has historically been administered orally, maintaining a predictable plasma concentration of the drug is challenging. As a result, enteral administration of carbidopa/levodopa (Duopa) has emerged as a promising tool in the treatment of the disease. This requires placement of an enteric catheter, two of which have been approved by the Food and Drug Administration for delivery of Duopa. The approved tubes are placed using the "peroral" or "pull" technique, a method traditionally requiring endoscopy. This technical note describes placement of the AbbVie PEG-J tube by means of the peroral route while utilizing only sonographic and fluoroscopic guidance. After placing an orogastric tube and achieving percutaneous access to the stomach under fluoroscopic visualization, a snare catheter is advanced through the percutaneous access into the stomach. The orogastric tube is engaged with the snare and retracted, bringing the attached snare with it to the mouth. The AbbVie PEG tube is attached to the snare, pulled back down the esophagus and into the stomach before being retracted through the percutaneous access to the skin. Finally, the AbbVie J tube is advanced through the gastrostomy tube into the proximal jejunum and attached with the provided connectors. As demonstrated, the AbbVie PEG-J tube can be placed safely and effectively using a percutaneous image-guided technique without the use of an endoscope.

Classification of advanced stages of Parkinson's disease: translation into stratified treatments

Advanced stages of Parkinson's disease (advPD) still impose a challenge in terms of classification and related stage-adapted treatment recommendations. Previous concepts that define advPD by certain milestones of motor disability apparently fall short in addressing the increasingly recognized complexity of motor and non-motor symptoms and do not allow to account for the clinical heterogeneity that require more personalized approaches. Therefore, deep phenotyping approaches are required to characterize the broad-scaled, continuous and multidimensional spectrum of disease-related motor and non-motor symptoms and their progression under real-life conditions. This will also facilitate the reasoning for clinical care and therapeutic decisions, as neurologists currently have to refer to clinical trials that provide guidance on a group level; however, this does not always account for the individual needs of patients. Here, we provide an overview on different classifications for advPD that translate into critical phenotypic patterns requiring the differential therapeutic adjustments. New concepts refer to precision medicine approaches also in PD and first studies on genetic stratification for therapeutic outcomes provide a potential for more objective treatment recommendations. We define novel treatment targets that align with this concept and make use of emerging device-based assessments of real-life information on PD symptoms. As these approaches require empowerment of patients and integration into treatment decisions, we present communication strategies and decision support based on new technologies to adjust treatment of advPD according to patient demands and safety.

High-Resolution Genetics Identifies the Lipid Transfer Protein Sec14p as Target for Antifungal Ergolines

Invasive infections by fungal pathogens cause more deaths than malaria worldwide. We found the ergoline compound NGx04 in an antifungal screen, with selectivity over mammalian cells. High-resolution chemogenomics identified the lipid transfer protein Sec14p as the target of NGx04 and compound-resistant mutations in Sec14p define compound-target interactions in the substrate binding pocket of the protein. Beyond its essential lipid transfer function in a variety of pathogenic fungi, Sec14p is also involved in secretion of virulence determinants essential for the pathogenicity of fungi such as Cryptococcus neoformans, making Sec14p an attractive antifungal target. Consistent with this dual function, we demonstrate that NGx04 inhibits the growth of two clinical isolates of C. neoformans and that NGx04-related compounds have equal and even higher potency against C. neoformans. Furthermore NGx04 analogues showed fungicidal activity against a fluconazole resistant C. neoformans strain. In summary, we present genetic evidence that NGx04 inhibits fungal Sec14p and initial data supporting NGx04 as a novel antifungal starting point.

Emerging resistance to antibiotics led to an inglorious revival of infectious diseases. Furthermore, in the past 30 years, only one novel anti-fungal target has been discovered which was used to develop therapies against. Therefore pathogen-selective targets and knowledge about possible resistance determinants are of utmost importance to successfully develop new medicines. Here we describe the identification of anti-fungal ergolines, targeting the lipid transfer protein Sec14p, and inhibiting the growth of two clinical isolates of the pathogenic fungus Cryptococcus neoformans. Both, compound and target represent attractive points for further investigations: Sec14p as it differs significantly from the human homolog and as it has been implicated in fungal viability and pathogenicity, and, ergolines as they are used in the clinic against a variety of diseases demonstrating both efficacy and safety.

Nanomedicine to Overcome Current Parkinson's Treatment Liabilities: A Systematic Review

Nanoparticles might be produced and manipulated to present a large spectrum of properties. The physicochemical features of the engineered nanomaterials confer to them different features, including the ability to cross the blood-brain barrier. The main objective of this review is to present the state-of-art research in nano manipulation concerning Parkinson's disease (PD). In the past few years, the association of drugs with nanoparticles solidly improved treatment outcomes. We systematically reviewed 28 studies, describing their potential contributions regarding the role of nanomedicine to increase the efficacy of known pharmacological strategies for PD treatment. Data from animal models resulted in the (i) improvement of pharmacological properties, (ii) more stable drug concentrations, (iii) longer half-live and (iv) attenuation of pharmacological adverse effects. As this approach is recent, with many of the described works being published less than 5 years ago, the expectancy is that this knowledge gives support to an improvement in the current clinical methods to the management of PD and other neurodegenerative diseases.

Duration of drug action of dopamine D2 agonists in mice with 6-hydroxydopamine-induced lesions

Although 6-hydroxydopamine-induced (6-OHDA-induced) rats are a well-known Parkinson's disease model, the effects of dopamine D2 agonists in mice with 6-OHDA-induced lesions are not completely understood. We produced mice with 6-OHDA-induced lesions and measured their total locomotion counts following administration of several dopamine D2 agonists (pramipexole, ropinirole, cabergoline, rotigotine, apomorphine, talipexole, and quinelorane). Cabergoline showed the longest duration of drug action, which was in agreement with its long-lived anti-Parkinson effects in rats and humans. In contrast, pramipexole and ropinirole had notably short durations of drug action. We demonstrated that mice with 6-OHDA-induced lesions accompanied with significant lesions in the striatum may be reasonable models to predict the action duration of anti-Parkinson drug candidates in humans.

Multi-Drug-Loaded Microcapsules with Controlled Release for Management of Parkinson's Disease

Parkinson's disease (PD) is a progressive disease of the nervous system, and is currently managed through commercial tablets that do not sufficiently enable controlled, sustained release capabilities. It is hypothesized that a drug delivery system that provides controlled and sustained release of PD drugs would afford better management of PD. Hollow microcapsules composed of poly-l-lactide (PLLA) and poly (caprolactone) (PCL) are prepared through a modified double-emulsion technique. They are loaded with three PD drugs, i.e., levodopa (LD), carbidopa (CD), and entacapone (ENT), at a ratio of 4:1:8, similar to commercial PD tablets. LD and CD are localized in both the hollow cavity and PLLA/PCL shell, while ENT is localized in the PLLA/PCL shell. Release kinetics of hydrophobic ENT is observed to be relatively slow as compared to the other hydrophilic drugs. It is further hypothesized that encapsulating ENT into PCL as a surface coating onto these microcapsules can aid in accelerating its release. Now, these spray-coated hollow microcapsules exhibit similar release kinetics, according to Higuchi's rate, for all three drugs. The results suggest that multiple drug encapsulation of LD, CD, and ENT in gastric floating microcapsules could be further developed for in vivo evaluation for the management of PD.

Laparoscopic gastrojejunostomy for superior mesenteric artery syndrome in a patient with Parkinson's disease

INTRODUCTION

Superior mesenteric artery syndrome is rare cause of intestinal obstruction. We report an unusual case of a patient with Parkinson's disease who developed superior mesenteric artery syndrome and discuss her management including laparoscopic gastrojejunostomy and Roux-en-Y anastomosis.

CASE PRESENTATION

A 78-year-old patient with advanced Parkinson's disease presented with significant malnutrition, vomiting and post-prandial abdominal pain. Computed tomography confirmed duodenal compression by the superior mesenteric artery. We hypothesised this was likely triggered by extreme weight loss associated with advanced Parkinson's disease. As the patient failed to improve with conservative measures, laparoscopic gastrojejunostomy and Roux-en-Y anastomosis was successfully performed without complications and the patient discharged on day 7.

CONCLUSION

Successful treatment was achieved due to early recognition of the consequences of chronic illness and addressing malnutrition. From this experience, we propose that laparoscopic gastric bypass is a safe and minimally invasive effective treatment option for superior mesenteric artery syndrome.

Pharmacokinetics of Levodopa before and after Gastrointestinal Resection in Parkinson's Disease

Introduction

Levodopa (LD) is important in the clinical treatment of Parkinson's disease (PD), and the changes of its pharmacokinetics may affect the clinical outcome. LD is mainly absorbed in the upper intestine; thus, the pharmacokinetics of LD may change after gastrointestinal operation. Here, we present the case of a patient who underwent resection of the intestine and compared his LD pharmacokinetics before and after resection.

Case Presentation

A 72-year-old Japanese male PD patient developed jaundice and was diagnosed with cholangiocarcinoma. Pancreaticoduodenectomy was performed and part of the stomach, total duodenum, and part of the jejunum were resected. The patient had been treated with LD, and his pharmacokinetics was checked twice at the age of 68 years. Because LD is absorbed in the duodenum and jejunum, we checked his pharmacokinetics again after the operation. The results before the operation were almost similar; however, in comparison, the area under the curve and peak drug concentration was reduced, and the time-to-peak drug concentration and elimination halftime were elongated after the operation.

Conclusion

Physicians must pay attention to the change of LD pharmacokinetics after gastrointestinal operation.

New levodopa therapeutic strategies

During its almost half-century of use for treating Parkinson's disease, levodopa therapy has permitted most patients to reverse much of this disorder's symptomatology. However, the full range of its therapeutic properties is not completely understood, as levodopa is showing itself to be more than just a metabolic intermediate for dopamine synthesis. Improving the constancy of drug delivery is the next frontier for enhancing therapeutic options with levodopa. Because conventional immediate-release carbidopa-levodopa tablets yield such variable pharmacokinetic profiles (as do other marketed products attempting to extend levodopa effect), improved formulations are greatly needed by patients experiencing motor fluctuations. Products under development or recently released in the U.S. include intestinal infusion, sustained-release microtablets, gastric-retentive formulations, a levodopa pro-drug, and methods for delivery of the drug by inhalation or subcutaneous infusion.

L-Dopa Pharmacokinetic Profile with Effervescent Melevodopa/Carbidopa versus Standard-Release Levodopa/Carbidopa Tablets in Parkinson's Disease: A Randomised Study

Objectives. To characterize the pharmacokinetic profile of levodopa (L-dopa) and carbidopa after repeated doses of the effervescent tablet of melevodopa/carbidopa (V1512; Sirio) compared with standard-release L-dopa/carbidopa in patients with fluctuating Parkinson's disease. Few studies assessed the pharmacokinetics of carbidopa to date. Methods. This was a single-centre, randomized, double-blind, double-dummy, two-period crossover study. Patients received V1512 (melevodopa 100 mg/carbidopa 25 mg) or L-dopa 100 mg/carbidopa 25 mg, 7 doses over 24 hours (Cohort 1), 4 doses over 12 hours (Cohort 2), or 2 doses over 12 hours in combination with entacapone 200 mg (Cohort 3). Pharmacokinetic parameters included area under the plasma-concentration time curve (AUC), maximum plasma concentration (C_max), and time to C_max (t_max). Results. Twenty-five patients received at least one dose of study medication. L-dopa absorption tended to be quicker and pharmacokinetic parameters less variable after V1512 versus L-dopa/carbidopa, both over time and between patients. Accumulation of L-dopa in plasma was less noticeable with V1512. Carbidopa exposure and interpatient variability was lower when V1512 or L-dopa/carbidopa was given in combination with entacapone. Both treatments were well tolerated. Conclusions. V1512 provides a more reliable L-dopa pharmacokinetic profile versus standard-release L-dopa/carbidopa, with less drug accumulation and less variability. This trial is registered with ClinicalTrials.gov NCT00491998.

Comparison of the pharmacokinetics of an oral extended-release capsule formulation of carbidopa-levodopa (IPX066) with immediate-release carbidopa-levodopa (Sinemet(®)), sustained-release carbidopa-levodopa (Sinemet(®) CR), and carbidopa-levodopa-entacapone (Stalevo(®))

IPX066 (extended‐release carbidopa‐levodopa [ER CD‐LD]) is an oral extended‐release capsule formulation of carbidopa and levodopa. The single‐dose pharmacokinetics of ER CD‐LD (as 2 capsules; total dose, 97.5 mg‐390 mg CD‐LD) versus immediate‐release (IR) CD‐LD (25 mg‐100 mg), sustained‐release (CR) CD‐LD (25 mg‐100 mg), and CD‐LD‐entacapone (25 mg‐100 mg‐200 mg) was evaluated in healthy subjects. Following IR dosing, LD reached peak concentrations (C_max) at 1 hour; LD concentrations then decreased rapidly and were less than 10% of peak by 5 hours. With CR CD‐LD and CD‐LD‐entacapone, LD C_max occurred at 1.5 hours, and concentrations were less than 10% of peak by 6.3 and 7.5 hours, respectively. The initial increase in LD concentration was similar between ER CD‐LD and IR CD‐LD and faster than for CR CD‐LD and CD‐LD‐entacapone. LD concentrations from ER CD­­‐LD were sustained for approximately 5 hours and did not decrease to 10% of peak until 10.1 hours. Dose‐normalized LD C_max values for ER CD‐LD were significantly lower (P< .05) than for the other CD‐LD products. Bioavailability of LD from ER CD‐LD was 83.5%, 78.3%, and 58.8% relative to IR CD‐LD, CR CD‐LD, and CD‐LD‐entacapone, respectively.