Pharmacokinetics of levodopa

Adaptive, personalized closed-loop therapy for Parkinson's disease: biochemical, neurophysiological, and wearable sensing systems

INTRODUCTION

Motor complication management is one of the main unmet needs in Parkinson's disease patients.

AREAS COVERED

Among the most promising emerging approaches for handling motor complications in Parkinson's disease, adaptive deep brain stimulation strategies operating in closed-loop have emerged as pivotal to deliver sustained, near-to-physiological inputs to dysfunctional basal ganglia-cortical circuits over time. Existing sensing systems that can provide feedback signals to close the loop include biochemical-, neurophysiological- or wearable-sensors. Biochemical sensing allows to directly monitor the pharmacokinetic and pharmacodynamic of antiparkinsonian drugs and metabolites. Neurophysiological sensing relies on neurotechnologies to sense cortical or subcortical brain activity and extract real-time correlates of symptom intensity or symptom control during DBS. A more direct representation of the symptom state, particularly the phenomenological differentiation and quantification of motor symptoms, can be realized via wearable sensor technology.

EXPERT OPINION

Biochemical, neurophysiologic, and wearable-based biomarkers are promising technological tools that either individually or in combination could guide adaptive therapy for Parkinson's disease motor symptoms in the future.

Microbes, metabolites and (synaptic) malleability, oh my! The effect of the microbiome on synaptic plasticity

The microbiome influences the emotional and cognitive phenotype of its host, as well as the neurodevelopment and pathophysiology of various brain processes and disorders, via the well‐established microbiome–gut–brain axis. Rapidly accumulating data link the microbiome to severe neuropsychiatric disorders in humans, including schizophrenia, Alzheimer's and Parkinson's. Moreover, preclinical work has shown that perturbation of the microbiome is closely associated with social, cognitive and behavioural deficits. The potential of the microbiome as a diagnostic and therapeutic tool is currently undercut by a lack of clear mechanistic understanding of the microbiome–gut–brain axis. This review establishes the hypothesis that the mechanism by which this influence is carried out is synaptic plasticity – long‐term changes to the physical and functional neuronal structures that enable the brain to undertake learning, memory formation, emotional regulation and more. By examining the different constituents of the microbiome–gut–brain axis through the lens of synaptic plasticity, this review explores the diverse aspects by which the microbiome shapes the behaviour and mental wellbeing of the host. Key elements of this complex bi‐directional relationship include neurotransmitters, neuronal electrophysiology, immune mediators that engage with both the central and enteric nervous systems and signalling cascades that trigger long‐term potentiation of synapses. The importance of establishing mechanistic correlations along the microbiome–gut–brain axis cannot be overstated as they hold the potential for furthering current understanding regarding the vast fields of neuroscience and neuropsychiatry. This review strives to elucidate the promising theory of microbiome‐driven synaptic plasticity in the hope of enlightening current researchers and inspiring future ones.

Could New Generations of Sensors Reshape the Management of Parkinson’s Disease?

Parkinson's disease (PD) is a chronic neurologic disease that has a great impact on the patient’s quality of life. The natural course of the disease is characterized by an insidious onset of symptoms, such as rest tremor, shuffling gait, bradykinesia, followed by improvement with the initiation of dopaminergic therapy. However, this “honeymoon period” gradually comes to an end with the emergence of motor fluctuations and dyskinesia. PD patients need long-term treatments and monitoring throughout the day; however, clinical examinations in hospitals are often not sufficient for optimal management of the disease. Technology-based devices are a new comprehensive assessment method of PD patient’s symptoms that are easy to use and give unbiased measurements. This review article provides an exhaustive overview of motor complications of advanced PD and new approaches to the management of the disease using sensors.

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.

Deciphering Spinal Endogenous Dopaminergic Mechanisms That Modulate Micturition Reflexes in Rats with Spinal Cord Injury

Spinal neuronal mechanisms regulate recovered involuntary micturition after spinal cord injury (SCI). It was recently discovered that dopamine (DA) is synthesized in the rat injured spinal cord and is involved in lower urinary tract (LUT) activity. To fully understand the role of spinal DAergic machinery in micturition, we examined urodynamic responses in female rats during pharmacological modulation of the DA pathway. Three to four weeks after complete thoracic SCI, the DA precursor L-DOPA administered intravenously during bladder cystometrogram (CMG) and external urethral sphincter (EUS) electromyography (EMG) reduced bladder overactivity and increased the duration of EUS bursting, leading to remarkably improved voiding efficiency. Apomorphine (APO), a non-selective DA receptor (DR) agonist, or quinpirole, a selective DR₂ agonist, induced similar responses, whereas a specific DR₂ antagonist remoxipride alone had only minimal effects. Meanwhile, administration of SCH 23390, a DR₁ antagonist, reduced voiding efficiency by increasing tonic EUS activity and shortening the EUS bursting period. Unexpectedly, SKF 38393, a selective DR₁ agonist, increased EUS tonic activity, implying a complicated role of DR₁ in LUT function. In metabolic cage assays, subcutaneous administration of quinpirole decreased spontaneous voiding frequency and increased voiding volume; L-DOPA and APO were inactive possibly because of slow entry into the CNS. Collectively, tonically active DR₁ in SCI rats inhibit urine storage and enhance voiding by differentially modulating EUS tonic and bursting patterns, respectively, while pharmacologic activation of DR₂, which are normally silent, improves voiding by enhancing EUS bursting. Thus, enhancing DA signaling achieves better detrusor-sphincter coordination to facilitate micturition function in SCI rats.

Non-Invasive Sweat-Based Tracking of L-Dopa Pharmacokinetic Profiles Following an Oral Tablet Administration

Levodopa (L-Dopa) is the "gold-standard" medication for symptomatic therapy of Parkinson disease (PD). However, L-Dopa long-term use is associated with the development of motor and non-motor complications, primarily due to its fluctuating plasma levels in combination with the disease progression. Herein, we present the first example of individualized therapeutic drug monitoring for subjects upon intake of standard L-Dopa oral pill, centered on dynamic tracking of the drug concentration in naturally secreted fingertip sweat. The touch-based non-invasive detection method relies on instantaneous collection of fingertip sweat on a highly permeable hydrogel that transports the sweat to a biocatalytic tyrosinase-modified electrode, where sweat L-Dopa is measured by reduction of the dopaquinone enzymatic product. Personalized dose-response relationship is demonstrated within a group of human subjects, along with close pharmacokinetic correlation between the finger touch-based fingertip sweat and capillary blood samples.

Dietary Approaches to Improve Efficacy and Control Side Effects of Levodopa Therapy in Parkinson's Disease: A Systematic Review

Although levodopa remains the most effective drug for symptomatic management of Parkinson's Disease (PD), treatment during advanced disease stages may raise unpredictable motor fluctuations and other complications. Counteracting these complications with other pharmacological therapies may prompt a vicious circle of side effects, and here, nutritional therapy may have great potential. Knowledge about the role of diet in PD is emerging and multiple studies have investigated nutritional support specifically with respect to levodopa therapy. With this systematic review, we aim to give a comprehensive overview of dietary approaches to optimize levodopa treatment in PD. A systematic search was performed using the databases of PubMed and Scopus between January 1985 and September 2020. Nutritional interventions with the rationale to optimize levodopa therapy in human PD patients were eligible for this study and their quality was assessed with the Cochrane risk-of-bias tool. In total, we included 22 papers that addressed the effects of dietary proteins (n = 10), vitamins (n = 7), fiber (n = 2), soybeans (n = 1), caffeine (n = 1), and ketogenic diets (n = 1) on levodopa therapy. Interventions with protein redistribution diets (PRDs), dietary fiber, vitamin C, and caffeine improved levodopa absorption, thereby enhancing clinical response and reducing motor fluctuations. Furthermore, supplementation of vitamin B-12, vitamin B-6, and folic acid successfully reduced high homocysteine concentrations that emerged from levodopa metabolism and promoted many metabolic and clinical complications, such as neuropathology and osteoporosis. In conclusion, dietary interventions have the potential to optimize levodopa efficacy and control side effects. Nutrition that improves levodopa absorption, including PRDs, fiber, vitamin C, and caffeine, is specifically recommended when fluctuating clinical responses appear. Supplements of vitamin B-12, vitamin B-6, and folic acid are advised along with levodopa initiation to attenuate hyperhomocysteinemia, and importantly, their potential to treat consequent metabolic and clinical complications warrants future research.

Design, synthesis and evaluation of 3-hydroxypyridin-4-ones as inhibitors of catechol-O-methyltransferase

The most effective treatment of Parkinson's disease is restoring central dopamine levels with levodopa, the metabolic precursor of dopamine. However, due to extensive peripheral metabolism by aromatic L-amino acid decarboxylase and catechol-O-methyltransferase (COMT), only a fraction of the levodopa dose reaches the brain unchanged. Thus, by preventing levodopa metabolism and increasing the availability of levodopa for uptake into the brain, the inhibition of COMT would be beneficial in Parkinson's disease. Although nitrocatechol COMT inhibitors have been used in the treatment of Parkinson's disease, efforts have been made to discover non-nitrocatechol inhibitors. In the present study, the 3-hydroxypyridin-4-one scaffold was selected for the design and synthesis of non-nitrocatechol COMT inhibitors since the COMT inhibitory potential of this class has been illustrated. Using COMT obtained from porcine liver, it was shown that a synthetic series of ten 3-hydroxypyridin-4-ones are in vitro inhibitors with IC50 values ranging from 4.55 to 19.8 µM. Although these compounds are not highly potent inhibitors, they may act as leads for the development of non-nitrocatechol COMT inhibitors. Such compounds would be appropriate for the treatment of Parkinson's disease. 3-Hydroxypyridin-4-ones have been synthesised and evaluated as non-nitrocatechol COMT inhibitors. In vitro, the IC50 values ranged from 4.55 to 19.8 μM.

Intelligent automated drug administration and therapy: future of healthcare

In the twenty-first century, the collaboration of control engineering and the healthcare sector has matured to some extent; however, the future will have promising opportunities, vast applications, and some challenges. Due to advancements in processing speed, the closed-loop administration of drugs has gained popularity for critically ill patients in intensive care units and routine life such as personalized drug delivery or implantable therapeutic devices. For developing a closed-loop drug delivery system, the control system works with a group of technologies like sensors, micromachining, wireless technologies, and pharmaceuticals. Recently, the integration of artificial intelligence techniques such as fuzzy logic, neural network, and reinforcement learning with the closed-loop drug delivery systems has brought their applications closer to fully intelligent automatic healthcare systems. This review's main objectives are to discuss the current developments, possibilities, and future visions in closed-loop drug delivery systems, for providing treatment to patients suffering from chronic diseases. It summarizes the present insight of closed-loop drug delivery/therapy for diabetes, gastrointestinal tract disease, cancer, anesthesia administration, cardiac ailments, and neurological disorders, from a perspective to show the research in the area of control theory.

No effect of a dopaminergic modulation fMRI task by amisulpride and L-DOPA on reward anticipation in healthy volunteers

RATIONALE

Dysregulation of dopaminergic neurotransmission, specifically altered reward processing assessed via the reward anticipation in the MID task, plays a central role in the etiopathogenesis of neuropsychiatric disorders.

OBJECTIVES

We hypothesized to find a difference in the activity level of the reward system (measured by the proxy reward anticipation) under drug administration versus placebo, in that amisulpride reduces, and L-DOPA enhances, its activity.

METHODS

We studied the influence of dopamine agonist L-DOPA and the antagonist amisulpride on the reward system using functional magnetic resonance imaging (fMRI) during a monetary incentive delay (MID) task in n = 45 healthy volunteers in a randomized, blinded, cross-over study.

RESULTS

The MID paradigm elicits strong activation in reward-dependent structures (such as ventral striatum, putamen, caudate, anterior insula) during reward anticipation. The placebo effect demonstrated the expected significant blood oxygen level-dependent activity in reward-dependent brain regions. Neither amisulpride nor L-DOPA led to significant changes in comparison with the placebo condition. This was true for whole-brain analysis as well as analysis of a pre-defined nucleus accumbens region-of-interest mask.

CONCLUSION

The present results cast doubt on the sensitivity of reward anticipation contrast in the MID task for assessing dopamine-specific changes in healthy volunteers by pharmaco-fMRI. While our task was not well-suited for detailed analysis of the outcome phase, we provide reasonable arguments that the lack of effect in the anticipation phase is not due to an inefficient task but points to unexpected behavior of the reward system during pharmacological challenge. Group differences of reward anticipation should therefore not be seen as simple representatives of dopaminergic states.

High levodopa plasma concentration after oral administration predicts levodopa-induced dyskinesia in Parkinson's disease

INTRODUCTION

In patients with Parkinson's disease (PD), pulsatile dopaminergic stimulation may be a primary cause of levodopa-induced dyskinesia (LID). We aimed to investigate the correlation between levodopa pharmacokinetics (PK) and LID in PD.

METHODS

We retrospectively reviewed the consecutive series of 255 PD patients without LID who underwent PK assessments with 100 mg levodopa. The type of peripheral decarboxylase inhibitor used in the PK assessments was determined by the usual prescription of the formulations of levodopa (10 mg carbidopa [n = 185] and 25 mg benserazide [n = 70]).

RESULTS

During a median follow-up of 32 months (IQR, 16-49 months), 73 patients (29%) developed LID. Compared with patients who did not develop LID (PD-LID-), those who developed LID (PD-LID+) were younger (p = 0.003) and had significantly higher maximum levodopa concentration (Cmax) (p = 0.002) and area under the curve (p < 0.001), LEDD (p < 0.001), and improvement of motor symptoms (p = 0.009). In the multivariate Cox proportional hazards models, Cmax and AUC were associated with incident LID (Hazard Ratio [HR] 1.11, 95% confidence interval [CI] 1.03-1.19 and HR 1.13, 95% CI 1.03-1.24, respectively). In addition, younger age, benserazide use, LEDD, and MAOBI use were associated with incident LID.

CONCLUSION

High levodopa plasma concentration after oral administration was associated with incident LID in patients with PD.

Self-assembled polydopamine nanoparticles improve treatment in Parkinson's disease model mice and suppress dopamine-induced dyskinesia

Although Levodopa (l-DOPA), a dopamine precursor, exhibits a high risk of dyskinesia, it remains the primary treatment in Parkinson's disease (PD), a progressive neurodegenerative disorder. In this study, we designed poly(l-DOPA)-based self-assembled nanodrug (Nano^DOPA) from amphiphilic block copolymer possessing poly(l-DOPA(OAc)₂), which is a precursor of l-DOPA as a hydrophobic segment, for treatment in a PD model mouse. Under physiological enzyme treatment, the poly(l-DOPA(OAc)₂) in the block copolymer was hydrolyzed to liberate l-DOPA gradually. Using the MPTP-induced PD mouse model, we observed that mice treated with Nano^DOPA demonstrated a significant improvement of PD symptoms compared to the l-DOPA treatment. Interestingly, the Nano^DOPA treatment did not cause the dyskinesia symptoms, which was clearly observed in the l-DOPA-treated mice. Furthermore, Nano^DOPA exhibited remarkably lower toxicity in vitro compared to l-DOPA, in addition with no noticeable Nano^DOPA toxicity observed in the treated mice. These results suggested that self-assembled Nano^DOPA is a promising therapeutic in the treatment of PD. STATEMENT OF SIGNIFICANCE: In this study, we proposed a therapeutic approach for the effective treatment of Parkinson's disease (PD) using newly designed poly(l-DOPA)-based self-assembled nanodrug (Nano^DOPA) prepared from amphiphilic block copolymers possessing poly(l-DOPA(OAc)₂), which is a precursor of l-DOPA as a hydrophobic segment, for treatment in a PD model mouse. Under physiological enzyme treatments, Nano^DOPA was hydrolyzed to liberate l-DOPA gradually, improving the pharmacokinetic value of l-DOPA. The mice treated with Nano^DOPA significantly improved PD symptoms compared to the l-DOPA treatment in a neurotoxin-induced PD mouse model. Interestingly, Nano^DOPA treatment did not cause dyskinesia symptoms, which was observed in the l-DOPA-treated mice. The obtained results in this study suggested that self-assembled Nano^DOPA is a promising therapeutic in the treatment of PD.

Long-term effectiveness of levodopa-carbidopa intestinal gel on motor and non-motor symptoms in advanced Parkinson's disease: results of the Italian GLORIA patient population

Introduction

The GLORIA registry included 375 advanced Parkinson’s disease (PD) patients and evaluated the efficacy and safety of a 24-month levodopa-carbidopa intestinal gel (LCIG) treatment in routine medical care. This analysis focuses on the Italian population, 60 patients treated with LCIG in 7 specialised PD care centres.

Methods

Hours of “Off” and “On” time were assessed with a modified version of the Unified Parkinson’s Disease Rating Scale (UPDRS) part IV items 39 and 32. Motor fluctuations, dyskinesia, non-motor symptoms, quality of life and safety were evaluated.

Results

Overall, 42 (70%) out of 60 patients completed the registry. LCIG treatment reduced “Off” time (− 3.3 ± 2.7 h at month 24 (M24), P < 0.0001), increased “On” time with dyskinesia (− 2.6 ± 5.2 h at M12, P = 0.0160), and improved UPDRS II and UPDRS III total scores at M24 (− 4.5 ± 10.6, P = 0.0333 and − 4.9 ± 11.7, P = 0.0229, respectively), Non-Motor Symptom Scale (NMSS) total score (− 21.8 ± 28.5, P < 0.0001) and Parkinson’s Disease Questionnaire-8 item (PDQ-8) total score (− 12.5 ± 23.9, P = 0.0173) versus previous oral therapy. Adverse drug reactions (ADR) possibly or probably related to treatment were reported in 16 (28.6%) patients. Decreased weight (7.1%), polyneuropathy (7.1%) and abdominal pain (5.4%) were the most frequent ADRs while device malfunction (5.4%) and medical device change (5.4%) were the most reported device complaints.

Conclusions

LCIG improved motor fluctuations, non-motor symptoms and quality of life over 24 months while tolerability was consistent with the established safety profile.

The TANDEM investigation: efficacy and tolerability of levodopa-carbidopa intestinal gel in (LCIG) advanced Parkinson's disease patients

The TANDEM investigation was carried out in 17 Italian Movement Disorder centers on behalf of a joint initiative of neurologist members of the Italian Academy for Parkinson's disease and Movement Disorders (LIMPE-DISMOV Academy) and gastroenterologist members of the Italian Society of Digestive Endoscopy (SIED) to evaluate the efficacy and tolerability of levodopa-carbidopa intestinal gel (LCIG) in patients with advanced Parkinson's disease (PD) in routine medical care. Motor scores in "ON" and OFF" state (UPDRS-III), complications of therapy (UPDRS-IV), activities of daily living, sleep disorders and quality of life were evaluated at baseline and at two follow-up assessments (FUV1 and FUV2) within the initial 12-month LCIG treatment. In 159 patients (55% males) with a mean age of 69.1 ± 6.6 years and a diagnosis of PD since 13.6 ± 5.5 years, the UPDRS-III total score (in "OFF") decreased from baseline (45.8 ± 13.2) to FUV1 (41.0 ± 17.4; p < 0.001) and FUV2 (40.5 ± 15.5; p < 0.001), the UPDRS-IV total score decreased from baseline (8.8 ± 2.9) to FUV1 (5.1 ± 3.4; p < 0.001) and FUV2 (5.5 ± 3.2; p < 0.001). The percentage of patients exhibiting freezing, dystonia, gait/walking disturbances, falls, pain and sleep disorders was significantly reduced. Twenty-eight device complications were reported and 11 (6.9%) patients prematurely terminated the study. LCIG after 12-month treatment led to sustained improvement of time spent in "OFF", complications of therapy, PD-associated symptoms and sleep disorders. LCIG tolerability was consistent with the established safety profile of LCIG.

Effects of daily L-dopa administration on learning and brain structure in older adults undergoing cognitive training: a randomised clinical trial

Cognitive aging creates major individual and societal burden, motivating search for treatment and preventive care strategies. Behavioural interventions can improve cognitive performance in older age, but effects are small. Basic research has implicated dopaminergic signalling in plasticity. We investigated whether supplementation with the dopamine-precursor L-dopa improves effects of cognitive training on performance. Sixty-three participants for this randomised, parallel-group, double-blind, placebo-controlled trial were recruited via newspaper advertisements. Inclusion criteria were: age of 65–75 years, Mini-Mental State Examination score >25, absence of serious medical conditions. Eligible subjects were randomly allocated to either receive 100/25 mg L-dopa/benserazide (n = 32) or placebo (n = 31) prior to each of twenty cognitive training sessions administered during a four-week period. Participants and staff were blinded to group assignment. Primary outcomes were latent variables of spatial and verbal fluid intelligence. Compared to the placebo group, subjects receiving L-dopa improved less in spatial intelligence (−0.267 SDs; 95%CI [−0.498, −0.036]; p = 0.024). Change in verbal intelligence did not significantly differ between the groups (−0.081 SDs, 95%CI [−0.242, 0.080]; p = 0.323). Subjects receiving L-dopa also progressed slower through the training and the groups displayed differential volumetric changes in the midbrain. No statistically significant differences were found for the secondary cognitive outcomes. Adverse events occurred for 10 (31%) and 7 (23%) participants in the active and control groups, correspondingly. The results speak against early pharmacological interventions in older healthy adults to improve broader cognitive functions by targeting the dopaminergic system and provide no support for learning-enhancing properties of L-dopa supplements in the healthy elderly. The findings warrant closer investigation about the cognitive effects of early dopamine-replacement therapy in neurological disorders. This trial was preregistered at the European Clinical Trial Registry, EudraCT#2016-000891-54 (2016-10-05).

Mathematical modeling and parameter estimation of levodopa motor response in patients with parkinson disease

Parkinson disease (PD) is characterized by a clear beneficial motor response to levodopa (LD) treatment. However, with disease progression and longer LD exposure, drug-related motor fluctuations usually occur. Recognition of the individual relationship between LD concentration and its effect may be difficult, due to the complexity and variability of the mechanisms involved. This work proposes an innovative procedure for the automatic estimation of LD pharmacokinetics and pharmacodynamics parameters, by a biologically-inspired mathematical model. An original issue, compared with previous similar studies, is that the model comprises not only a compartmental description of LD pharmacokinetics in plasma and its effect on the striatal neurons, but also a neurocomputational model of basal ganglia action selection. Parameter estimation was achieved on 26 patients (13 with stable and 13 with fluctuating LD response) to mimic plasma LD concentration and alternate finger tapping frequency along four hours after LD administration, automatically minimizing a cost function of the difference between simulated and clinical data points. Results show that individual data can be satisfactorily simulated in all patients and that significant differences exist in the estimated parameters between the two groups. Specifically, the drug removal rate from the effect compartment, and the Hill coefficient of the concentration-effect relationship were significantly higher in the fluctuating than in the stable group. The model, with individualized parameters, may be used to reach a deeper comprehension of the PD mechanisms, mimic the effect of medication, and, based on the predicted neural responses, plan the correct management and design innovative therapeutic procedures.

Little Change in Functional Brain Networks Following Acute Levodopa in Drug-Naïve Parkinson's Disease

OBJECTIVE

The objective of this study was to investigate the effects of levodopa on functional brain networks in Parkinson's disease.

METHODS

We acquired resting state functional magnetic resonance imaging in 30 drug-naïve participants with Parkinson's disease and 20 age-matched healthy controls. Each participant was studied following administration of a single oral dose of either levodopa or placebo in a randomized, double-blind, crossover design.

RESULTS

The greatest observed differences in functional connectivity were between Parkinson's disease versus control participants, independent of pharmacologic intervention. By contrast, the effects of levodopa were much smaller and detectable only in the Parkinson's disease group. Moreover, although levodopa administration in the Parkinson's disease group measurably improved motor performance, it did not increase the similarity of functional connectivity in Parkinson's disease to the control group.

CONCLUSIONS

We found that a single, small dose of levodopa did not normalize functional connectivity in drug-naïve Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.

Amisulpride and l-DOPA modulate subcortical brain nuclei connectivity in resting-state pharmacologic magnetic resonance imaging

The precise understanding of the dopaminergic (DA) system and its pharmacological modifications is crucial for diagnosis and treatment of neuropsychiatric disorders, as well as for understanding basic processes, such as motivation and reward. We probed the functional connectivity (FC) of subcortical nuclei related to the DA system according to seed regions defined according to an atlas of subcortical nuclei. We conducted a large pharmaco‐fMRI study using a double‐blind, placebo‐controlled design, where we examined the effect of l‐DOPA, a dopamine precursor, and amisulpride, a D2/D3‐receptor antagonist on resting‐state FC in 45 healthy young adults using a cross‐over design. We examined the FC of subcortical nuclei with connection to the reward system and their reaction to opposing pharmacological probing. Amisulpride increased FC from the putamen to the precuneus and from ventral striatum to precentral gyrus. l‐DOPA increased FC from the ventral tegmental area (VTA) to the insula/operculum and between ventral striatum and ventrolateral prefrontal cortex and it disrupted ventral striatal and dorsal caudate FC with the medial prefrontal cortex. In an exploratory analysis, we demonstrated that higher self‐rated impulsivity goes together with a significant increase in VTA‐mid‐cingulate gyrus FC during l‐DOPA‐challenge. Therefore, our DA challenge modulated distinct large‐scale subcortical connectivity networks. A dopamine‐boost can increase midbrain DA nuclei connectivity to the cortex. The involvement of the VTA‐cingulum connectivity in dependence of impulsivity has implications for diagnosis and therapy in disorders like ADHD.

Are There Benefits in Adding Catechol-O Methyltransferase Inhibitors in the Pharmacotherapy of Parkinson's Disease Patients? A Systematic Review

BACKGROUND

A qualified consensus suggests that a combination of levodopa with a peripherally acting dopa decarboxylase inhibitor continues to present the gold standard treatment of Parkinson's disease (PD). However, as the disease progresses the therapeutic window of levodopa becomes narrowed. Pharmacological strategies for motor fluctuations are focused on providing less pulsatile and more continuous dopaminergic stimulation. Peripheral catechol-O-methyltransferase (COMT) inhibition improves the bioavailability of levodopa and results in a prolonged response.

OBJECTIVE

The primary aim of this study was to investigate the efficacy and safety of the two available COMT inhibitors; entacapone and tolcapone and the recently introduced opicapone.

METHODS

Electronic databases were systematically searched for original studies published within the last 37 years. In addition, lists of identified studies, reviews and their references were examined.

RESULTS

Twelve studies fulfilled the inclusion criteria. 3701 patients with PD were included in this systematic review.

CONCLUSIONS

Adjuvant treatment of PD patients experiencing motor fluctuations with entacapone resulted in improvement of motor function and was well tolerated. Therefore, entacapone presented an acceptable benefit to risk ratio. Tolcapone appeared to result in a greater therapeutic effect. However, this was not consistent across all motor variables and studies, and thus would not support its use, given the current onerous monitoring that is required. Opicapone was not associated with adverse reactions in a phase III trial but did not present a greater efficacy than entacapone, and thus further studies are required in order to illustrate its cost effectiveness.

Development, Optimization, and Evaluation In Vitro/In Vivo of Oral Liquid System for Synchronized Sustained Release of Levodopa/Benserazide

To enhance efficiency, convenience, and safety of Parkinson's disease (PD) treatment for geriatric patients, an advanced suspension of Levodopa/Benserazide hydrochloride (LD/BH) has been prepared by cation-exchange resin and used to synchronize sustained release of LD and BH by optimizing coating parameters and prescription. For the purpose, LD and BH were immobilized on the surface of cation-exchange resin, respectively. Based on HPLC results, the cation-exchange resin showed high loading capacity. The studies on drug loading mechanism indicated that both drugs were immobilized by electrostatic interaction rather than physical adsorption. After PEG modification, pretreated drug-resin complexes were coated by emulsion-solvent evaporation method. In order to control drug release in a sustained manner, coating parameters of drug-resin microcapsules were optimized respectively by single-factor analysis. Further, coating prescription of the microcapsules was optimized to synchronize sustained release of LD and BH in vitro by orthogonal design. Utilizing optimal LD-resin microcapsules and BH-resin microcapsules, LD/BH suspension, containing both of them, was prepared by an optimal formulation and characterized by accelerated test and pharmacokinetic study in vivo. The accelerated test confirmed high stability of LD/BH suspension. According to pharmacokinetic results in vivo, in contrast with LD/BH commercial tablets, LD/BH suspensions did not only synchronize sustained release of both drugs but also show good bioequivalence. As LD/BH sustained release suspension can synchronize sustained release of multiple active ingredients by oral administration, the suspension presents promising oral dosage forms for geriatric patients with PD. An advanced Levodopa/Benserazide hydrochloride (LD/BH) suspension, prepared by cation-exchange resin and optimized microencapsulation, synchronizes sustained releases of LD and BH in vivo to benefit Parkinson's disease treatment for geriatric patients.

Pharmacokinetics of Nanosomal Form of Levodopa in Intranasal Administration

BACKGROUND:

Parkinson’s disease is one of the most common neurological diseases. Pathogenesis of the disease is associated with destruction and death of neurons that produce the neurotransmitter dopamine. The precursor to dopamine, which crosses the protective blood-brain barrier, is the amino acid 3, 4-dihydroxy-L-phenylalanine – levodopa, L-DOPA. The investigational drug is a pharmaceutical composition, containing L-DOPA as an active substance, which is distributed in a polymer matrix based on a biodegradable copolymer of lactic/glycolic acids.

AIM:

This work aimed to study the main pharmacokinetic parameters for the drug “L-DOPA – PC, nasal drops” and comparator drugs “L-DOPA in oil”, “L-DOPA – PC in purified water”, reference product – tablets “Madopar 125”.

METHODS:

To increase the bioavailability of the active substance L-DOPA, a new route of administration was used for the first time – nasal administration. Pharmacokinetics of the innovative drug with the intranasal route of administration was investigated in rabbits. The L-DOPA concentration in blood plasma was determined by high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS).

RESULTS:

Bioavailability of the drug – nasal drops were 244.4% compared with the drug “Madopar 125”.

CONCLUSION:

Assay procedure for the determination of L-DOPA in animal blood plasma using liquid chromatography with tandem mass-selective detection (HPLC-MS/MS) was developed and validated.

Conditioned pain modulation in drug-naïve patients with de novo Parkinson's disease

Background

Pain is highly prevalent in patients with Parkinson’s disease (PD), but underlying pathophysiological mechanisms are largely unclear. In many chronic pain syndromes deficits in endogenous pain inhibition have been detected that can be assessed using conditioned pain modulation paradigms. Previous studies employing this approach in medicated PD patients did not find abnormal pain inhibition. However, these results might have been confounded by residual dopaminergic medication.

Methods

An established conditioned pain modulation paradigm was used in 17 drug-naïve de novo PD patients and 17 healthy age and gender-matched controls. We tested i) whether conditioned pain modulation responses differed between the patient and control group and ii) whether pain inhibition differed between PD subtypes.

Results

PD patients and healthy controls did not differ in their conditioned pain modulation responses. Furthermore, there were no significant differences in CPM responses depending on the PD subtype. However, at a descriptive level, tremor-dominant patients showed a tendency for better descending pain inhibition compared to akinetic-rigid and mixed type patients.

Conclusions

In this first study investigating conditioned pain modulation in de novo PD patients, we found no additional impairment in descending pain modulation besides the known age-related decline. Our findings indicate that mechanisms other than an impaired descending inhibition contribute to high pain prevalence rates in PD and suggest that mechanisms underlying pain may differ between PD subtypes.

Electronic supplementary material

The online version of this article (10.1186/s42466-019-0029-x) contains supplementary material, which is available to authorized users.

Evaluation of Selected Natural Compounds as Dual Inhibitors of Catechol-O-Methyltransferase and Monoamine Oxidase

Background:

The most effective symptomatic treatment of Parkinson’s disease remains the metabolic precursor of dopamine, L-dopa. To enhance the efficacy of L-dopa, it is often combined with inhibitors of the enzymes, catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) B, key metabolic enzymes of L-dopa and dopamine.

Objective:

This study attempted to discover compounds that exhibit dual inhibition of COMT and MAO-B among a library of 40 structurally diverse natural compounds. Such dual acting inhibitors may be effective as adjuncts to L-dopa and offer enhanced value in the management of Parkinson’s disease.

Methods:

Selected natural compounds were evaluated as in vitro inhibitors of rat liver COMT and recombinant human MAO. Reversibility of MAO inhibition was investigated by dialysis.

Results:

Among the natural compounds morin (IC50 = 1.32 µM), chlorogenic acid (IC50 = 6.17 µM), (+)-catechin (IC50 = 0.86 µM), alizarin (IC50 = 0.88 µM), fisetin (IC50 = 5.78 µM) and rutin (IC50 = 25.3 µM) exhibited COMT inhibition. Among these active COMT inhibitors only morin (IC50 = 16.2 µM), alizarin (IC50 = 8.16 µM) and fisetin (IC50 = 7.33 µM) were noteworthy MAO inhibitors, with specificity for MAO-A.

Conclusion:

None of the natural products investigated here are dual COMT/MAO-B inhibitors. However, good potency COMT inhibitors have been identified, which may serve as leads for future development of COMT inhibitors.

Using Spontaneous Eye-blink Rates to Predict the Motor Status of Patients with Parkinson's Disease

Objective Assessing daily motor fluctuations is an important part of the disease management for patients with Parkinson's disease (PD). However, the frequent recording of subjective and/or objective assessments is not always feasible, and easier monitoring methods have been sought. Previous studies have reported that the spontaneous eye-blink rate (EBR) is correlated with the dopamine levels in the brain. Thus, the continuous monitoring of the EBR may be useful for predicting the motor status in patients with PD. Methods Electrooculograms (EOGs) were recorded for up to 7.5 hours from three PD patients using a wearable device that resembled ordinary glasses. An receiver operating characteristic (ROC) analysis was performed to compare the ability of the EBR estimates at each time-point (Blink Index) and the plasma levodopa levels to predict the motor status. Results The Blink Index was correlated with the plasma levodopa levels. When an indicator for the first hour of the observation period was included in the model, the Blink Index discerned wearing-off and dyskinesia as accurately as the plasma levodopa level. Conclusion Our study provides preliminary evidence regarding the utility of continuous EBR monitoring for the non-invasive evaluation of the motor status in patients with PD.

Dopamine-dependent prefrontal reactivations explain long-term benefit of fear extinction

Fear extinction does not prevent post-traumatic stress or have long-term therapeutic benefits in fear-related disorders unless extinction memories are easily retrieved at later encounters with the once-threatening stimulus. Previous research in rodents has pointed towards a role for spontaneous prefrontal activity occurring after extinction learning in stabilizing and consolidating extinction memories. In other memory domains spontaneous post-learning activity has been linked to dopamine. Here, we show that a neural activation pattern - evoked in the ventromedial prefrontal cortex (vmPFC) by the unexpected omission of the feared outcome during extinction learning - spontaneously reappears during postextinction rest. The number of spontaneous vmPFC pattern reactivations predicts extinction memory retrieval and vmPFC activation at test 24 h later. Critically, pharmacologically enhancing dopaminergic activity during extinction consolidation amplifies spontaneous vmPFC reactivations and correspondingly improves extinction memory retrieval at test. Hence, a spontaneous dopamine-dependent memory consolidation-based mechanism may underlie the long-term behavioral effects of fear extinction.

A proof-of-principle study of the effect of combined haloperidol and levodopa administration on working memory-related brain activation in humans

OBJECTIVE

Cognitive deficits including impaired working memory are a hallmark feature of schizophrenia. Dopamine D1 receptor modulated changes in prefrontal cortex function play a potentially important role in the pathology underlying such deficits. However, pharmacological interventions that selectively engage the D1 receptor are severely restricted for research in humans. The present study is a proof-of-principle for enhancing cognitive performance and associated brain activation via indirect D1 stimulation, operationalised by combining the nonselective dopamine agonist L-dopa with the D2-antagonist haloperidol.

METHODS

Fourteen healthy volunteers received placebo or combined carbidopa (25 mg)/L-dopa (100 mg) plus haloperidol (2 mg) orally on two separate occasions according to a within-subjects crossover design. Drug-induced differences in brain activity were assessed during an N-back working memory task in a 3T magnetic resonance imaging environment.

RESULTS

Drug treatment was associated with greater functional connectivity between the dorsolateral prefrontal cortex and areas within the salience network during all N-back trials. Drug treatment was also associated with reduced activation, most prominently in the occipital/temporal brain areas during 2-back performance.

CONCLUSIONS

This preliminary study provides initial evidence for combined L-dopa/haloperidol modulation in cognition-related brain areas and networks, which is relevant for the treatment of cognitive impairments in mental illness.

Impaired tissue barriers as potential therapeutic targets for Parkinson's disease and amyotrophic lateral sclerosis

The blood-brain barrier and the intestinal barrier show signs of disruption in patients with idiopathic Parkinson's disease (PD) and animal models of nigrostriatal degeneration, and likewise in amyotrophic lateral sclerosis (ALS) models. A substantial body of evidence shows that defects in epithelial membrane barriers, both in the gut and within the cerebral vasculature, can result in increased vulnerability of tissues to external factors potentially participating in the pathogenesis of PD and ALS. As such, restoration of tissue barriers may prove to be a novel therapeutic target in neurodegenerative disease. In this review, we focus on the potential of new intervention strategies for rescuing and maintaining barrier functions in PD and ALS.

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.

Profile of inhaled levodopa and its potential in the treatment of Parkinson's disease: evidence to date

Inhaled levodopa is a newly emerging therapeutic option in the treatment of "off " symptoms associated with Parkinson's disease (PD). Its mode of delivery offers more rapid absorption of levodopa and shorter onset of clinical benefit compared to oral formulations, and has been shown to be feasible for use in patients with PD experiencing worse motor function due to declining plasma levodopa levels. Clinical development of this compound is supported by preclinical, Phase I-III, long-term-safety studies and studies in special populations, including otherwise-healthy asthmatics and smokers. These investigations demonstrated that the drug is well tolerated without risk of long-term (up to 1 year) changes in pulmonary function or spirometry measures. The most common side effects among PD patients were a mild cough, upper respiratory tract infection, nausea, sputum discoloration, and dyskinesia. Inhaled levodopa offers a different administration method and side-effect profile from the currently available options for rescue therapy for Off periods in PD, though comparative studies have not been performed. The drug is presently under review by the US Food and Drug Administration.

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.

The Design and Evaluation of an l-Dopa-Lazabemide Prodrug for the Treatment of Parkinson's Disease

l-Dopa, the metabolic precursor of dopamine, is the treatment of choice for the symptomatic relief of the advanced stages of Parkinson’s disease. The oral bioavailability of l-dopa, however, is only about 10% to 30%, and less than 1% of the oral dose is estimated to reach the brain unchanged. l-Dopa’s physicochemical properties are responsible for its poor bioavailability, short half-life and the wide range of inter- and intrapatient variations of plasma levels. An l-dopa–lazabemide prodrug is proposed to overcome the problems associated with l-dopa absorption. Lazabemide is a monoamine oxidase (MAO)-B inhibitor, a class of compounds that slows the depletion of dopamine stores in Parkinson’s disease and elevates dopamine levels produced by exogenously administered l-dopa. l-Dopa was linked at the carboxylate with the primary aminyl functional group of lazabemide via an amide, a strategy which is anticipated to protect l-dopa against peripheral decarboxylation and possibly also enhance the membrane permeability of the prodrug. Selected physicochemical and biochemical properties of the prodrug were determined and included lipophilicity (logD), solubility, passive diffusion permeability, pK_a, chemical and metabolic stability as well as cytotoxicity. Although oral and i.p. treatment of mice with the prodrug did not result in enhanced striatal dopamine levels, 3,4-dihydroxyphenylacetic acid (DOPAC) levels were significantly depressed compared to saline, l-dopa and carbidopa/l-dopa treatment. Based on the results, further preclinical evaluation of the l-dopa–lazabemide prodrug should be undertaken with the aim of discovering prodrugs that may be advanced to the clinical stages of development.

Effect of Levodopa-carbidopa Intestinal Gel on Non-motor Symptoms in Patients with Advanced Parkinson's Disease

Background

Levodopa‐carbidopa intestinal gel (LCIG; carbidopa‐levodopa enteral suspension in the United States), delivered via percutaneous gastrojejunostomy (PEG‐J) and titrated in the inpatient setting, is an established treatment option for advanced Parkinson's disease (PD) patients with motor fluctuations. However, long‐term prospective data on the efficacy of LCIG on non‐motor symptoms and the safety of outpatient titration are limited.

Methods

In this 60‐week, open‐label phase 3b study, LCIG titration was initiated in an outpatient setting following PEG‐J placement in PD patients. The efficacy of LCIG on motor and non‐motor symptoms, quality of life, and safety was assessed.

Results

Thirty‐nine patients were enrolled in the study and 28 patients completed the treatment. A majority of patients (54%) completed outpatient titration within the first week of LCIG infusion. LCIG led to significant reductions from baseline in Non‐Motor Symptom Scale (NMSS) total score (least squares mean ± SE = −17.6 ± 3.6, P < 0.001) and 6 of the NMSS domain scores (sleep/fatigue, attention/memory, gastrointestinal tract, urinary, sexual function, miscellaneous) at week 12. These reductions were maintained at week 60 with the exception of the urinary domain. “Off” time (−4.9 ± 0.5 hours/day, P < 0.001) and “On” time without troublesome dyskinesia (−4.3 ± 0.6 hours/day, P < 0.001) were improved at week 60. Adverse events (AEs) were reported in 37 (95%) patients.

Conclusions

LCIG treatment led to reductions in non‐motor symptom burden and motor fluctuations in advanced PD patients. The safety profile was consistent with previous studies that used inpatient titration and outpatient titration did not appear to pose additional risk.

An Observational Study of the Effect of Levodopa-Carbidopa Intestinal Gel on Activities of Daily Living and Quality of Life in Advanced Parkinson's Disease Patients

Introduction

Continuous delivery of levodopa–carbidopa intestinal gel (LCIG) by percutaneous endoscopic gastrojejunostomy (PEG-J) in advanced Parkinson’s disease (PD) patients reduces variability in plasma levels, providing better control of motor fluctuations (“on” and “off” states). The MONOTREAT study assessed the effect of LCIG on activities of daily living, motor and non-motor symptoms, and quality of life in advanced PD patients.

Methods

This prospective, observational study included patients with advanced, levodopa-responsive PD with either 2–4 h of “off” time or 2 h of dyskinesia daily. Patients received LCIG via PEG-J for 16 h continuously. Effectiveness was assessed using Unified PD Rating Scale parts II and III, the Non-Motor Symptom Scale, and the PD Questionnaire-8.

Results

The mean (SD) treatment duration was 275 (157) days. Patients experienced significant improvement from baseline in activities of daily living at final visit (p < 0.05) as well as at months 3 and 6 (p < 0.0001). Patients also experienced significant improvements from baseline in quality of life and non-motor symptoms at all time points (p < 0.001 for all). Specifically, patients manifested significant improvements in mean change from baseline at every study visit in five of nine non-motor symptom score domains: sleep/fatigue, mood/cognition, gastrointestinal tract, urinary, and miscellaneous. One-third of patients (32.8%) experienced an adverse event; 21.9% experienced a serious adverse event; 11.1% discontinued because of an adverse event.

Conclusion

This study demonstrated significant and clinically relevant improvements in measures of activities of daily living, quality of life, and a specific subset of non-motor symptoms after treatment with LCIG.

Funding

AbbVie Inc.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-017-0571-2) contains supplementary material, which is available to authorized users.

Protein-Restricted Diets for Ameliorating Motor Fluctuations in Parkinson's Disease

Levodopa is considered to be the most effective symptomatic drug for Parkinson's disease (PD). As the disease progresses, however, the patients are likely to experience a reduced response to levodopa and develop motor fluctuations (i.e., end-of-dose wearing off and unpredictable "on-off"). Protein-rich diets and elevated plasma concentrations of large neutral amino acids have been proved to impair the therapeutic effect of levodopa by reducing its absorption and influx into the brain. On the other hand, the protein-restricted diets including low-protein diet (LPD), protein-redistribution diet (PRD) and PRD with use of low-protein products can all improve the efficacy of levodopa in patients with motor fluctuations. However, it should be noted that protein-restricted diets may also contribute to several side effects, including dyskinesia, weight loss, and malnutrition (e.g., protein and calcium insufficiency). Together, protein-restricted diets are an effective approach to improve motor fluctuations in PD patients, while long-term adherence to these diets requires monitoring for side effects.

Motor Complications of Dopaminergic Medications in Parkinson's Disease

Motor complications are a consequence of the chronic treatment of Parkinson's disease (PD) and include motor fluctuations (wearing-off phenomenon) and levodopa-induced dyskinesia. Both can have a significant impact on functionality and quality of life; thus, proper recognition and management is essential. The phenomenology and temporal relationship of motor complications to the schedule of levodopa dosing can be helpful in characterizing them. There are several therapeutic approaches to motor complications, including pharmacological and surgical options. The authors summarize the different types of motor complications according to phenomenology and the currently available medical treatments, including ongoing trials for the management of this condition.

Liquid levodopa-carbidopa in advanced Parkinson's disease with motor complications

While levodopa, carbidopa, ascorbic acid solution (LCAS) therapy has been used in patients with advanced Parkinson's disease (PD) for many years, long-term follow-up data is scarce. The present study aimed to determine the long-term retention rate for LCAS therapy, and to identify the causes of LCAS therapy withdrawal. Our study included a series of 38 patients with PD (14 men and 24 women) who underwent LCAS treatment between 2011 and 2013 to alleviate motor complications that were not satisfactorily controlled by optimized conventional anti-parkinsonian treatment at the Seoul National University Hospital. All patients were admitted to educate them about and initiate LCAS treatment for 2-5days, and were then followed up as outpatients. The mean follow-up duration was 12.8months, and three main reasons for LCAS treatment discontinuation were worsening of wearing-off symptoms (8 patients), persistent dyskinesia (4 patients), and poor drug adherence (4 patients). Fourteen patients (36.8%) maintained the LCAS treatment after 12months, and were categorized as the treatment-retention group. The mean percentage of on time without dyskinesia significantly increased from 33.6±17.6% to 57.0±27.7% after LCAS initiation (p=0.016) in the treatment-retention group. Twelve patients (31.6%) were still receiving LCAS treatment after 30months. LCAS treatment can be a non-device assisted therapeutic option for patients who have no access to advanced therapies such as deep brain stimulation and infusional treatments.

Efficacy and safety of levodopa-carbidopa intestinal gel from a study in Japanese, Taiwanese, and Korean advanced Parkinson's disease patients

In a previous multinational, randomized, double-blind, double-dummy study, levodopa–carbidopa intestinal gel (LCIG) was tolerable and significantly improved ‘off’ time in advanced Parkinson’s disease (PD) patients. However, efficacy and safety in the Asian population has not yet been demonstrated. In this open-label study, efficacy and safety of LCIG were assessed in Japanese, Korean, and Taiwanese advanced PD patients with motor complications not adequately controlled by available PD medication. The patients were treated with LCIG monotherapy for 12 weeks. The primary end point was the mean change from baseline to week 12 in ‘off’ time, as reported in the PD Symptom Diary, normalized to a 16 h waking day and analyzed by a mixed-model repeated-measures analysis. Adverse events (AEs) were recorded. Thirty-one patients were enrolled (23 Japanese, 4 Taiwanese, 4 Korean) and 28 (90%) completed the study. For those who completed the study, the mean (s.d.) total daily levodopa dose from LCIG was 1,206.3 (493.6) mg/day at final visit (n=28); last observation carried forward (n=30) was 1,227.6 (482.8) mg/day. There was a significant mean change (s.d.) of −4.6 (3.0) hours of ‘off’ time from baseline (mean (s.d.)=7.4 (2.3)) to week 12 (n=29), P<0.001. All the patients had an AE, with the most frequently reported being incision site pain (42%); 1 (3.2%) discontinued treatment because of an AE and later died because of sepsis, which the investigator considered unrelated to LCIG treatment. These results suggest that LCIG is efficacious and tolerable in Japanese, Taiwanese, and Korean advanced PD patients.