Plasma Levodopa Concentrations Research Articles

Therapeutic drug monitoring in Parkinson's disease.

A patient-tailored therapy of the heterogeneous, neuropsychiatric disorder of Parkinson's disease (PD) aims to improve dopamine sensitive motor symptoms and associated non-motor features. A repeated, individual adaptation of dopamine substituting compounds is required throughout the disease course due to the progress of neurodegeneration. Therapeutic drug monitoring of dopamine substituting drugs may be an essential tool to optimize drug applications. We suggest plasma determination of levodopa as an initial step. The complex pharmacology of levodopa is influenced by its short elimination half-life and the gastric emptying velocity. Both considerably contribute to the observed variability of plasma concentrations of levodopa and its metabolite 3-O-methyldopa. These amino acids compete with other aromatic amino acids as well as branched chain amino acids on the limited transport capacity in the gastrointestinal tract and the blood brain barrier. However, not much is known about plasma concentrations of levodopa and other drugs/drug combinations in PD. Some examples may illustrate this lack of knowledge: Levodopa measurements may allow further insights in the phenomenon of inappropriate levodopa response. They may result from missing compliance, interactions e.g. with treatments for other mainly age-related disorders, like hypertension, diabetes, hyperlipidaemia, rheumatism or by patients themselves independently taken herbal medicines. Indeed, uncontrolled combination of compounds for accompanying disorders as given above with PD drugs might increase the risk of side effects. Determination of other drugs used to treat PD in plasma such as dopamine receptor agonists, amantadine and inhibitors of catechol-O-methyltransferase or monoamine oxidase B may refine and improve the value of calculations of levodopa equivalents. How COMT-Is change levodopa plasma concentrations? How other dopaminergic and non-dopaminergic drugs influence levodopa levels? Also, delivery of drugs as well as single and repeated dosing and continuous levodopa administrations with a possible accumulation of levodopa, pharmacokinetic behaviour of generic and branded compounds appear to have a marked influence on efficacy of drug treatment and side effect profile. Their increase over time may reflect progression of PD to a certain degree. Therapeutic drug monitoring in PD is considered to improve the therapeutic efficacy in the course of this devastating neurologic disorder and therefore is able to contribute to the patients' precision medicine. State-of-the-art clinical studies are urgently needed to demonstrate the usefulness of TDM for optimizing the treatment of PD.

Effect of concomitant use of esomeprazole on levodopa pharmacokinetics and clinical symptoms in patients with Parkinson's disease

BackgroundProton pump inhibitors (PPIs), which inhibit gastric acid secretion, are frequently prescribed to patients with Parkinson's disease (PD). Levodopa, the gold-standard treatment for PD, demonstrates enhanced solubility in acidic environments. Although PPIs increase gastric pH and may affect levodopa absorption, the effect of concomitant PPI use on levodopa pharmacokinetics in patients with PD remains unknown. This study aimed to investigate the effect of the concomitant use of esomeprazole, a PPI, on the pharmacokinetics of levodopa and carbidopa and clinical symptoms in patients with PD. MethodsWe prospectively enrolled 40 patients with PD and compared the pharmacokinetics of levodopa and carbidopa and clinical symptoms before and two weeks after the concomitant use of esomeprazole. ResultsThe plasma concentrations of levodopa 30 min after concomitant oral administration of levodopa and esomeprazole were significantly lower (4.92 ± 4.10 μmol/L) than those without concomitant esomeprazole use (6.26 ± 3.75 μmol/L; p = 0.027). The plasma concentrations of carbidopa showed no significant differences with respect to concomitant esomeprazole use. Significant elevation was recorded in all subscores of the Movement Disorder Society-sponsored revision of the Unified Parkinson's disease Rating Scale scores after concomitant use of esomeprazole. No significant differences were observed between Helicobacter pylori-negative and Helicobacter pylori-positive patients. Non-elderly patients (age ≤ 70 years) tended to be more susceptible to the effect of esomeprazole on levodopa pharmacokinetics and clinical symptoms. ConclusionsThe unnecessary use of PPIs should be avoided in patients with PD, especially in non-elderly patients, to improve absorption of levodopa.

Association between Fecal Bile Acids and Levodopa Response in Patients with Parkinson's Disease.

Levodopa is the mainstay of treatments for Parkinson's disease (PD), but large heterogeneity exists in patient response. Increasing evidence implicates bile acids (BAs) involved in the pathogenesis of PD. Furthermore, BAs have also participated in drug bioavailability. However, the impact of BAs on levodopa response (LR) has not been investigated. This study evaluated the association between fecal BAs and LR. Levodopa challenge test (LCT) was conducted in 92 PD patients to assess LR. A total of 36 fecal BAs and plasma levodopa concentrations were detected using LC-MS/MS. The difference of BAs between subgroups with bottom and top 30% LR were analyzed and fecal samples from the two groups were collected for metagenomic shotgun analysis. No fecal BAs were significantly correlated with LR, except for chenodeoxycholic acid-3-β-D-glucuronide (CDCA-3-β-glucuronide, R = -0.228, p-value = 0.039). We found no significant difference in BAs between subgroups with bottom and top 30% LR. What is more, no significant changes in bacterial species composition related to bile acids metabolism or in the proportional representation of genes encoding known bile acids enzymes were observed between the groups. Overall, our data do not support an association between fecal BAs and levodopa response in PD patients. More precise macro-metabolomic approaches are needed to reveal the potential association between gut microbial interactions and the treatment effect of levodopa.

Potential Psychosis Induced by Sustained High Plasma Levodopa Concentration via Continuous Subcutaneous Foslevodopa/Foscarbidopa Infusion in Parkinson’s Disease: A Case Report

Potential Psychosis Induced by Sustained High Plasma Levodopa Concentration via Continuous Subcutaneous Foslevodopa/Foscarbidopa Infusion in Parkinson’s Disease: A Case Report

Motor Efficacy of Subcutaneous DIZ102, Intravenous DIZ101 or Intestinal Levodopa/Carbidopa Infusion.

It has been suggested that carbidopa at high blood concentrations may counter the therapeutic effect of levodopa in Parkinson's disease by entering the brain and blocking central levodopa conversion to dopamine. We previously demonstrated equivalent plasma levodopa concentration in patients with Parkinson's disease during 16 h of (1) intravenous carbidopa/levodopa (DIZ101) infusion, (2) subcutaneous carbidopa/levodopa (DIZ102) infusion or (3) intestinal carbidopa/levodopa gel infusion. Plasma levels of carbidopa were however approximately four times higher with DIZ101 and DIZ102 than with LCIG, and higher than those usually observed with oral levodopa/carbidopa. To investigate if high carbidopa blood concentrations obtained with parenteral levodopa/carbidopa (ratio 8:1) counter the effect of levodopa on motor symptoms. Eighteen patients with advanced Parkinson's disease were administered DIZ101, DIZ102, and intestinal levodopa/carbidopa gel for 16 h on different days in randomized order. Video recordings of a subset of the motor examination in the Unified Parkinson's Disease Rating Scale (UPDRS) were evaluated by raters blinded for treatment and time. Motor function was also measured using a wrist-worn device monitoring bradykinesia, dyskinesia, and tremor (Parkinson KinetiGraph). There was no tendency for poorer levodopa effect with DIZ101 or DIZ102 as compared to LCIG. Although DIZ101 or DIZ102 causes approximately four times higher plasma carbidopa levels than LCIG, patients responded equally well to all treatments. The results do not indicate that high plasma carbidopa levels hamper the motor efficacy of levodopa.

Continuous Levodopa Delivery with an Intraoral Micropump System: An Open-Label Pharmacokinetics and Clinical Study.

Double-blind studies have demonstrated that motor complications in Parkinson's disease (PD) can be reduced with continuous delivery of levodopa. The DopaFuse system is a novel, intraoral micropump that attaches to a retainer and uses a propellant to deliver levodopa/carbidopa (LD/CD) continuously into the mouth. Evaluate the safety, pharmacokinetics, and efficacy of LD/CD delivered via the DopaFuse system compared to treatment with intermittent doses of standard oral LD/CD in PD patients with motor fluctuations. This was a 2-week, open-label study (NCT04778176) in 16 PD patients treated with ≥4 levodopa doses/day and experiencing motor fluctuations. On Day 1 (clinic setting) patients received their usual dose of standard LD/CD; DopaFuse therapy was initiated on Day 2, and on Day 3 patients received DopaFuse plus a morning oral LD/CD dose. Patients returned home on Days 4-14 and returned for in-clinic assessment on Day 15. Continuous DopaFuse delivery of LD/CD was associated with reduced variability in plasma levodopa levels compared to oral LD/CD (mean ± SD levodopa Fluctuation Index reduced from 2.15 ± 0.59 on Day1 to 1.50 ± 0.55 on Day 2 (P = 0.0129) and to 1.03 ± 0.53 on Day 3 (P < 0.0001)). This pharmacokinetic improvement translated into significantly reduced OFF time with DopaFuse therapy (reduction of -1.72 ± 0.37 h at Day 15; P = 0.0004) and increased ON time without severe dyskinesias (increase of 1.72 ± 0.37 h at Day 15; P = 0.0004) versus oral LD/CD administration. DopaFuse therapy was not associated with any clinically significant adverse events. Continuous delivery of LD/CD using the DopaFuse system was associated with significantly less variability in plasma levodopa concentrations and reductions in OFF time compared to treatment with standard oral LD/CD therapy and was well tolerated. © 2024 International Parkinson and Movement Disorder Society.

Comparison of two types of extension tubes for people with Parkinson’s disease in advanced treatment with levodopa–entacapone–carbidopa intestinal gel infusions: a prospective, crossover quality study

BackgroundWithin Parkinson’s disease (PD) management, a pivotal juncture often arises when individuals with PD (PwP) necessitate advanced therapies to stabilise symptom fluctuations and reduce off-periods, which are intrinsic to living...

Optimization of oral entacapone administration in patients undergoing levodopa–carbidopa intestinal gel treatment

BackgroundLevodopa–carbidopa intestinal gel (LCIG) treatment markedly reduces motor fluctuations in patients with Parkinson's disease; however, some patients undergoing LCIG treatment may demonstrate clinical deterioration in the afternoon. Entacapone, a catechol-O-methyltransferase inhibitor, may be a promising adjunctive option for LCIG-treated patients; however, the optimal timing of oral entacapone administration to ameliorate clinical symptoms in the afternoon remains unexplored. This study aimed to investigate the optimal timing of oral entacapone administration in patients with Parkinson's disease undergoing LCIG treatment. MethodsPharmacokinetic analysis and symptom assessment were performed on three days: a day without entacapone administration, day with oral entacapone administration at 13:00, and day with oral entacapone administration at 15:00. ResultsEight LCIG-treated patients were enrolled, of whom seven completed this study. The relative plasma concentrations of levodopa with entacapone administration at 13:00 were gradually increased, especially at 18:00 and were significantly higher than those without entacapone administration (127.10 ± 25.06% vs. 97.51 ± 22.20%). The relative plasma concentrations of 3-O-methyldopa were gradually increased without entacapone administration, whereas those with entacapone administration at 13:00 were lower than those without entacapone administration, especially at 17:00 (97.47 ± 3.70% vs. 110.71 ± 9.84%). Administering oral entacapone at 15:00 increased and decreased the relative plasma concentrations of levodopa and 3-O-methyldopa, respectively, but without significant difference. The “Off” time was shorter with entacapone administration at 13:00 (0.43 ± 0.79 h) and at 15:00 (0.57 ± 0.79 h) than that without entacapone administration (1.14 ± 1.46 h). ConclusionsThe concomitant use of oral entacapone in the early afternoon may be effective in improving afternoon symptoms in patients undergoing LCIG treatment.

The Clinical Development of Levodopa Inhalation Powder.

Oral levodopa is the most effective treatment for Parkinson disease, but OFF periods emerge over time. Gastrointestinal dysfunction and food effects impact levodopa absorption, contributing to unpredictable control of OFF periods. Inhaled levodopa powder (Inbrija) is approved for on-demand treatment of OFF periods in patients receiving oral levodopa-dopa decarboxylase inhibitors. The 84-mg dose is administered via a breath-actuated inhaler. It provides pulmonary delivery of levodopa to the systemic circulation and is taken when a patient has an OFF period in between doses of regular oral levodopa medication. The pivotal SPAN-PD trial in patients experiencing OFF periods on oral dopaminergic therapy showed that levodopa inhalation powder 84 mg produced significant improvement in Unified Parkinson Disease Rating Scale Part III score, as measured 30 minutes postdose at week 12, and improvement was seen as early as 10 minutes. More patients in the levodopa inhalation powder group turned ON within 60 minutes of treatment and remained ON at 60 minutes than in the placebo group. Levodopa inhalation powder can also be used to treat early-morning OFF periods and, when used for up to 12 months, produced no clinically significant differences in pulmonary function compared with an untreated cohort. Levodopa inhalation powder 84 mg increased plasma levodopa concentration rapidly and with less variability than oral levodopa/carbidopa (25/100 mg). Most common adverse event associated with levodopa inhalation powder is cough, found in ~15% of patients in the SPAN-PD trial; otherwise, reported adverse events were consistent with those known to be associated with oral levodopa.

Concomitant use of magnesium oxide significantly decreases absorption of levodopa preparations in patients with Parkinson’s disease

IntroductionConstipation is one of the most frequent non-motor symptoms of Parkinson's disease (PD), and magnesium oxide (MgO) is a frequently used laxative. This study aimed to investigate the effect of concomitant use of MgO on the pharmacokinetics of levodopa preparations in patients with PD. MethodsWe prospectively enrolled 35 patients with PD and compared the pharmacokinetics of levodopa and carbidopa and motor symptoms with and without MgO. The impact of alterations in pH and the addition of MgO on the solubility of levodopa formulations were also evaluated under in vitro conditions. ResultsConcomitant use of MgO significantly reduced the maximum plasma concentration of levodopa (Cmax) (from 7.66 ± 3.74 μmol/L to 5.82 ± 3.69 μmol/L; p = 0.006) and area under the plasma concentration–time curve 3 h after drug administration (AUC3h, from 9.64 ± 3.23 μmol·h/L to 7.39 ± 3.15 μmol·h/L; p < 0.001), and further decreased carbidopa Cmax (from 64.02 ± 27.02 ng/mL to 38.83 ± 21.94 μmol/L; p < 0.001) and AUC3h (from 130.58 ± 65.64 ng/mL to 76.48 ± 52.24 ng·h/mL; p < 0.001). The Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale part III score also deteriorated significantly (from 30.71 ± 11.34 to 32.06 ± 11.22; p = 0.007). MgO significantly affected the pharmacokinetics of levodopa and carbidopa. This also applied when the findings were analyzed by sex and age. In vitro dissolution experiments revealed a decrease in the relative concentrations of levodopa, carbidopa, and benserazide as the pH increased and in the presence of MgO suspension, with the most prominent impact on benserazide. ConclusionsConcomitant use of MgO and levodopa should be discouraged to improve levodopa absorption.

The pharmacokinetics of continuous subcutaneous levodopa/carbidopa infusion: Findings from the ND0612 clinical development program.

While treatment with levodopa remains the cornerstone of Parkinson's disease (PD) management, chronic oral therapy is often associated with the development of motor complications, that correlate to fluctuating levodopa plasma concentrations, limiting its clinical utility. Continuous infusion is considered to be the optimal delivery route for treating PD patients with motor fluctuations, but current infusion systems require invasive surgery. Subcutaneous infusion of (SC) levodopa has the potential to provide a better tolerated and more convenient route of continuous levodopa delivery. ND0612 is in development as a combination product providing continuous levodopa/carbidopa via a minimally invasive, subcutaneous delivery system for PD patients experiencing motor response fluctuations. We present pharmacokinetic results from a series of studies that analyzed plasma concentrations after SC levodopa delivery with ND0612 to inform the clinical development program. We performed a series of six Phase I and II studies to characterize the pharmacokinetics of levodopa and carbidopa derived from ND0612 infusion with/without adjunct oral therapy of the same ingredients. These studies were conducted in healthy volunteers and in PD patients experiencing motor response fluctuations while on their current levodopa therapy regimen. Taken together, the results demonstrate dose-proportionality dependent on rate of subcutaneous levodopa infusion leading to stable and sustained plasma concentrations of levodopa. Subcutaneous infusion of ND0612 administered with oral levodopa/carbidopa maintained near-constant, therapeutic levodopa plasma concentrations, thereby avoiding the troughs in levodopa plasma concentrations that are associated with OFF time in PD. The data generated in this series of studies also confirmed that a levodopa/carbidopa dose ratio of 8:1 would be the most reasonable choice for ND0612 development. This series of clinical pharmacokinetic studies have demonstrated that ND0612, administered continuously with a levodopa concentration of 60 mg/ml combined with carbidopa 7.5 mg/ml, and complemented with oral levodopa/carbidopa, is suitable for 24 h continuous administration in patients with PD. The stable plasma concentrations of levodopa achieved predict utility of ND0612 as a parenteral formulation for achieving clinically useful delivery of levodopa for PD patients.

How resistant are levodopa-resistant axial symptoms? Response of freezing, posture, and voice to increasing levodopa intestinal infusion rates in Parkinson disease.

Treatment of freezing of gait (FoG) and other Parkinson disease (PD) axial symptoms is challenging. Systematic assessments of axial symptoms at progressively increasing levodopa doses are lacking. We sought to analyze the resistance to high levodopa doses of FoG, posture, speech, and altered gait features presenting in daily-ON therapeutic condition. We performed a pre-/postinterventional study including patients treated with levodopa/carbidopa intestinal gel infusion (LCIG) with disabling FoG in daily-ON condition. Patients were evaluated at their usual LCIG infusion rate (T1), and 1 h after 1.5× (T2) and 2× (T3) increase of the LCIG infusion rate by quantitative outcome measures. The number of FoG episodes (primary outcome), posture, speech, and gait features were objectively quantified during a standardized test by a blinded rater. Changes in motor symptoms, dyskinesia, and plasma levodopa concentrations were also analyzed. We evaluated 16 patients with a mean age of 69 ± 9.4 years and treated with LCIG for a mean of 2.2± 2.1 years. FoG improved in 83.3% of patients by increasing the levodopa doses. The number of FoG episodes significantly decreased (mean=2.3 at T1, 1.7 at T2, 1.2 at T3; p= 0.013). Posture and speech features did not show significant changes, whereas stride length (p= 0.049), turn duration (p= 0.001), and turn velocity (p= 0.024) significantly improved on doubling the levodopa infusion rate. In a short-term evaluation, the increase of LCIG dose can improve "dopa-resistant" FoG and gait issues in most advanced PD patients with overall good control of motor symptoms in the absence of clinically significant dyskinesia.

Patient-specific in vitro drug release testing coupled with in silico PBPK modeling to forecast the in vivo performance of oral extended-release levodopa formulations in Parkinson’s disease patients

Biorelevant in vitro release models are valuable analytical tools for oral drug development but often tailored to gastrointestinal conditions in ‘average’ healthy adults. However, predicting in vivo performance in individual patients whose gastrointestinal conditions do not match those of healthy adults would be of great value for optimizing oral drug therapy for such patients. This study focused on establishing patient-specific in vitro and in silico models to predict the in vivo performance of levodopa extended-release products in Parkinson’s disease patients. Current knowledge on gastrointestinal conditions in these patients was incorporated into model development. Relevant in vivo pharmacokinetic data and patient-specific in vitro release data from a novel in vitro test setup were integrated into patient-specific physiologically-based pharmacokinetic models. AUC, cmax and tmax of the computed plasma profiles were calculated using PK-Sim®. For the products studied, levodopa plasma concentration–time profiles modeled using this novel approach compared far better with published average plasma profiles in Parkinson’s disease patients than those derived from in vitro release data obtained from the ‘average’ healthy adult setup. Although further work is needed, results of this study highlight the importance of addressing patient-specific gastrointestinal conditions when aiming to predict drug release in such specific patient groups.

Association Between Microbial Tyrosine Decarboxylase Gene and Levodopa Responsiveness in Patients With Parkinson Disease.

Interindividual variability in levodopa efficacy is a challenge for the personalized treatment of Parkinson disease (PD). Gut microbiota might represent a new approach for personalized medicine. Recently, a novel microbial levodopa metabolism pathway was identified, which is mediated by tyrosine decarboxylase mainly encoded by tyrosine decarboxylase gene (tyrDC) in Enterococcus faecalis. In this study, we aimed to identify whether the abundance of microbial tyrDC gene and E faecalis is associated with levodopa responsiveness and could predict the drug response. This cross-sectional study enrolled patients with PD between December 2019 and January 2022 and evaluated levodopa responsiveness using a levodopa challenge test. Patients were stratified into moderate and good responders based on levodopa responsiveness. The tyrDC gene and E. faecalis abundance in fecal samples were measured using quantitative real-time PCR. Plasma levodopa concentrations were measured using liquid chromatography-tandem mass spectrometry analysis. The predictive models for levodopa responsiveness were constructed and verified through cross-validation and external validation. A total of 101 patients with PD were enrolled in the primary cohort and 43 were enrolled in the external validation cohort. Moderate responders had higher abundances of the tyrDC gene (3.6 [3.1-4.3] vs 2.6 [2.1-2.9], p < 0.001) and E faecalis (3.2 [2.5-4.4] vs 2.6 [2.1-3.6], p = 0.010) than good responders. The tyrDC gene abundance was independently associated with levodopa responsiveness (OR: 5.848; 95% CI: 2.664-12.838; p < 0.001). Notably, tyrDC gene abundance showed certain discriminative power for levodopa responsiveness in primary cohort (sensitivity: 80.0%; specificity: 84.3%; area under the curve [AUC]: 0.85; 95% CI: 0.77-0.93; p < 0.001) and external validation cohort (sensitivity: 85.0%; specificity: 95.7%; AUC: 0.95; 95% CI: 0.89-1.02; p < 0.001). The prediction of levodopa responsiveness based on tyrDC gene abundance had good calibration and discrimination in cross-validation (C-index in training and test sets: 0.856 and 0.851, respectively) and external validation (C-index: 0.952). The microbial tyrDC gene abundance could serve as a potential biomarker of levodopa responsiveness. Novel strategies targeting the tyrDC gene may provide new approaches for personalized levodopa treatment.

Gastrointestinal Motility and Response to Levodopa in Parkinson's Disease: A Proof-of-Concept Study.

Simultaneous measurement of gastrointestinal transit time (GITT) and plasma levodopa concentration (PLC) is crucial to understanding the effect of dysfunctional motility on levodopa response in patients with Parkinson's disease (PwPD). The aim is to determine if altered segmental GITT correlates with clinical response and PLC variability in PwPD. Ten typical and 10 erratic responders ingested the SmartPill (SP) wireless motility capsule. Serial PLC and finger tapping, obtained every 30minutes for 3 hours after SP/levodopa ingestion, evaluated the correlation between GITT, clinical response, and PLC. Glucose breath testing assessed small intestinal bacterial overgrowth (SIBO). GITT was not significantly different in "typical" and "erratic" responders. SIBO was positive in half of the erratic and negative in most typical responders. SP is a feasible technology for assessing GITT in PwPD. A larger study may be able to significantly differentiate/correlate GITT in different segments of the GI tract with response to levodopa. © 2022 International Parkinson and Movement Disorder Society.

The Prephase Nursing in Levodopa Carbidopa Intestinal Gel Therapy.

INTRODUCTION: Parkinson disease (PD) affects approximately 1% of women and men worldwide, particularly older than 60 years. It is a multisystem and neurodegenerative disease with genetics and environmental factors that result in deficits in the production of neurotransmitters, including dopamine. The levodopa-carbidopa intestinal gel (LCIG) system delivers a continuous infusion of levodopa directly into the proximal small intestine via percutaneous endoscopic jejunostomy, largely bypassing gastric emptying and absorption problems and producing more stable plasma concentrations of levodopa, eliminating the development of motor complications (dyskinesias). The aim of this review was to summarize scientific evidence on the nursing role that, together with the multidisciplinary team, made the patient's choice in this therapeutic path (pre-LCIG phase). METHODS: A literature review was carried out, conducted on the MEDLINE databases (through PubMed), The Cochrane Library, Google Scholar, and CINAHL (through EBSCO). Relevant articles for the topic were found to identify indexed primary studies that investigated the relationship between the nurse and the patient/caregiver with PD who undertakes treatment with LCIG according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses checklist. RESULTS: Nineteen studies were included in the review. The selected studies suggested how the pre-LCIG phase of patient choice and the subsequent education and training could avoid selection errors for these therapeutic paths. CONCLUSION: Trained and specialized nursing staff who carry out an adequate pre-LCIG phase associated to the multidisciplinary team improved the choice of the patient and the start of treatment and, consequently, the quality of life of PD patients.

Erratum: Zhao et al., "Histochemical Characterization of the Dorsal Raphe-Periaqueductal Grey Dopamine Transporter Neurons Projecting to the Extended Amygdala".

<h3>Objective:</h3> Characterize the levodopa pharmacokinetic profile achieved with continuous subcutaneous administration of ND0612. <h3>Background:</h3> Continuous levodopa/carbidopa infusion is the optimal delivery route for patients with advanced Parkinson’s disease (PD), but current delivery systems require invasive surgical interventions. ND0612 is a proprietary liquid formulation of levodopa/carbidopa administrated subcutaneously through a mini-pump delivering a range of levodopa doses from 270mg/day to 720mg/day. <h3>Design/Methods:</h3> Two Phase II studies were performed. The first was a phase IIa study in which 16 PD patients were randomized to low-or high- dose ND0612 for 8-hours administration. The second was a double-blind, placebo-controlled study, in which 30 PD patients received low dose ND0612 or placebo, as adjunct to their current optimized oral treatment for 2-weeks, followed by a 1-week open label extension of ND0612 either with or without oral entacapone. <h3>Results:</h3> In the first study, fluctuations in levodopa plasma levels were markedly reduced (both doses) in comparison to baseline oral levodopa/carbidopa. Levodopa maximal plasma concentrations were dose proportionate; low and high ND0612 doses achieved 487ng/mL and 1454ng/ml respectively. Co-administration of entacapone BID increased levodopa plasma levels to 604ng/mL and 1844ng/mL in the low and high dose arms respectively. In the second study, adjunct treatment with low-dose ND0612 eliminated the levodopa troughs associated with oral levodopa/carbidopa. Furthermore, when oral levodopa was discontinued, peaks and troughs in levodopa plasma levels were abolished, and mean levodopa levels were maintained at 550ng/ml. Co-administered entacapone further increased levodopa levels to 800ng/ml. In addition, the trial met its futility analysis endpoint; adjunct ND0612 reduced mean OFF by 2.42h in clinic and 2.13h in pilot home diaries, (vs. 0.41h and 1.39h with optimized oral therapy and placebo). <h3>Conclusions:</h3> Subcutaneous administration of ND0612 provides steady, therapeutic levodopa plasma concentrations that were associated with clinical improvement, and may provide an effective, non-invasive alternative for continuous levodopa delivery. <b>Study Supported by:</b> NeuroDerm Ltd. <b>Disclosure:</b> Dr. Giladi has received personal compensation for activities with Teva-Lundbeck, Merz Inc., and UCB for activities with the Advisory Boards . f Teva-Lundbeck, Merz Inc. Dr. Giladi has received personal compensation for activities with Teva Israel, Intec Pharma and NeuroDerm Inc. as a consultant. Dr. Caraco has received personal compensation for activities with NeuroDerm Ltd. as a consultant. Dr. Caraco has received research support from NeuroDerm Ltd. Dr. Gurevich has nothing to disclose. Dr. Djaldetti has nothing to disclose. L. Adar has received personal compensation for activities with NeuroDerm Ltd. as an employee. Dr. Cohen has received personal compensation for activities with Neuroderm as an employee. Dr. Rahmilevich has received personal compensation for activities with NeuroDerm Ltd., a an employee. Dr. Oren has received personal compensation for activities with NeuroDerm Ltd.

Ascorbic acid can alleviate the degradation of levodopa and carbidopa induced by magnesium oxide.

IntroductionLevodopa and carbidopa are reported to be degraded by magnesium oxide (MgO), which is often used as a laxative for patients with Parkinson's disease (PD). Ascorbic acid (AsA) can stabilize levodopa and carbidopa solutions; however, the effect of AsA on the degradation of levodopa and carbidopa induced by MgO has not been fully investigated.MethodsThe effect of AsA was evaluated using in vitro examinations, compared with lemon juice, and by measuring the plasma concentration of levodopa in a patient with PD.ResultsIn vitro experiments showed that the relative concentrations of levodopa remained almost constant, and the relative concentrations of carbidopa decreased with time with addition of MgO. AsA mitigated this effect in a concentration‐dependent manner, whereas the addition of lemon juice caused little change, although the pH decreased to the same extent. The results of levodopa pharmacokinetics of the patient showed that the area under the plasma concentration‒time curve values from hour 0 to 8 were 53.00 μmol·h/L with regular administration and 67.27 μmol·h/L with co‐administration of AsA.ConclusionsAsA can mitigate the degradation of carbidopa induced by MgO and may contribute to improving the bioavailability of levodopa in patients with PD.

A technology evaluation of CVT-301 (Inbrija): an inhalable therapy for treatment of Parkinson’s disease

Introduction The most widely used pharmacological treatment for Parkinson’s disease is levodopa, the precursor for dopamine formation in the brain. With time, the effectiveness of levodopa declines, and patients experience motor fluctuations, or OFF periods. A levodopa formulation administered via a capsule-based oral inhaler provides a new delivery mechanism for levodopa that provides rapid relief of OFF periods. Areas covered CVT-301 is a dry powder formulation designed to supply levodopa to the systemic circulation via pulmonary absorption. The technology, pharmacokinetics, efficacy, and safety data of this formulation are presented. Expert opinion Oral inhalation is a novel method of administration for levodopa that bypasses the gastrointestinal tract, allowing levodopa to enter the systemic circulation rapidly and more reliably than oral medications. Gastrointestinal dysfunction, a common feature of Parkinson’s disease, can lead to impaired absorption of oral medications. Pulmonary delivery rapidly elevates levodopa plasma concentrations to provide relief of OFF periods for patients receiving oral levodopa.

ND0612 (levodopa/carbidopa for subcutaneous infusion) in patients with Parkinson's disease and motor response fluctuations: A randomized, placebo-controlled phase 2 study

IntroductionND0612 is a continuous, subcutaneous levodopa/carbidopa delivery system under development for patients with Parkinson's disease (PD) and motor fluctuations. MethodsThis was a randomized, placebo-controlled, double-blind, 2-period study evaluating the safety and pharmacokinetics of ND0612 in PD patients on an optimized oral levodopa regimen and experiencing ≥2 h/day of OFF time. During Period-1, patients received their current standard of care (SoC) levodopa/carbidopa and were randomized (2:1) to 14 days treatment with adjunct ND0612 (daily levodopa/carbidopa dose of 270/63 mg) or placebo infusion +SoC. During Period-2, 16 patients were randomized to receive 7 days treatment with ND0612 or ND0612 plus oral entacapone. Reduction in OFF time was analyzed as an exploratory measure using a futility design with a predefined margin of 1.6 h. ResultsND0612 was well-tolerated; most patients experienced infusion site nodules (95% vs. 56% with placebo), which all resolved without sequelae. Patients treated with adjunct ND0612 during Period-1 avoided deep troughs in levodopa plasma levels and had a decreased fluctuation index versus placebo (1.6 ± 0.5 vs 3.1 ± 1.6 at end of Period-1, respectively). In Period-2, the coadministration of entacapone with continuous ND0612 SC infusion translated to an increase in mean levodopa AUC0–10h compared to baseline. Exploratory efficacy analysis of Period 1 showed mean ± SD OFF time reductions of −2.13 ± 2.24 [90%CI: -2.8, ∞] hours (p = 0.84 using H0 of μ0 ≤-1.6). ConclusionLevodopa/carbidopa infusion with ND0612 was generally well-tolerated and resulted in reduced fluctuations in plasma levodopa concentrations when given with SoC oral levodopa. ND0612 met the efficacy endpoint for the futility design.