Transdermal Delivery of Pramipexole Using Microneedle Technology for the Potential Treatment of Parkinson's Disease

Parkinson's disease (PD) is a debilitating neurodegenerative disease primarily impacting neurons responsible for dopamine production within the brain. Pramipexole (PRA) is a dopamine agonist that is currently available in tablet form. However, individuals with PD commonly encounter difficulties with swallowing and gastrointestinal motility, making oral formulations less preferable. Microneedle (MN) patches represent innovative transdermal drug delivery devices capable of enhancing skin permeability through the creation of microconduits on the surface of the skin. MNs effectively reduce the barrier function of skin and facilitate the permeation of drugs. The work described here focuses on the development of polymeric MN systems designed to enhance the transdermal delivery of PRA. PRA was formulated into both dissolving MNs (DMNs) and directly compressed tablets (DCTs) to be used in conjunction with hydrogel-forming MNs (HFMNs). In vivo investigations using a Sprague-Dawley rat model examined, for the first time, if it was beneficial to prolong the application of DMNs and HFMNs beyond 24 h. Half of the patches in the MN cohorts were left in place for 24 h, whereas the other half remained in place for 5 days. Throughout the entire 5 day study, PRA plasma levels were monitored for all cohorts. This study confirmed the successful delivery of PRA from DMNs (Cmax = 511.00 ± 277.24 ng/mL, Tmax = 4 h) and HFMNs (Cmax = 328.30 ± 98.04 ng/mL, Tmax = 24 h). Notably, both types of MNs achieved sustained PRA plasma levels over a 5 day period. In contrast, following oral administration, PRA remained detectable in plasma for only 48 h, achieving a Cmax of 159.32 ± 113.43 ng/mL at 2 h. The HFMN that remained in place for 5 days demonstrated the most promising performance among all investigated formulations. Although in the early stages of development, the findings reported here offer a hopeful alternative to orally administered PRA. The sustained plasma profile observed here has the potential to reduce the frequency of PRA administration, potentially enhancing patient compliance and ultimately improving their quality of life. This work provides substantial evidence advocating the development of polymeric MN-mediated drug delivery systems to include sustained plasma levels of hydrophilic pharmaceuticals.

Population Pharmacokinetics of the Novel Adenosine A2A Antagonist/Inverse Agonist KW-6356 and Its Active Metabolite Following Single and Multiple Oral Administration in Healthy Individuals and Patients with Parkinson's Disease

KW-6356 is a selective antagonist and inverse agonist of the adenosine A2A receptor. The primary aim of the present analysis was to characterize the pharmacokinetics (PK) of KW-6356 and its active metabolite M6 in healthy subjects and patients with Parkinson's disease (PD). We pooled concentration-time data from healthy subjects and patients with PD who were administered KW-6356. Using these data, we developed a population PK model by sequentially fitting the KW-6356 parameters followed by the M6 parameters. A first-order absorption with a 1-compartment model for KW-6356 and a 1-compartment model for M6 best described the profiles. The covariates included in the final models were food status (fed/fasted/unknown) on first-order absorption rate constant, baseline serum albumin level on apparent clearance of KW-6356, and baseline body weight on apparent volume of distribution of KW-6356 and apparent clearance of M6. No covariate had a clinically meaningful impact on KW-6356 or M6 exposure.

Clinical trial evaluating apomorphine oromucosal solution in Parkinson's disease patients

Apomorphine, used to treat OFF episodes in patients with Parkinson's disease (PD), is typically administered via subcutaneous injections. Administration of an oromucosal solution could offer a non-invasive and user-friendly alternative. This two-part clinical study evaluated the safety, tolerability, pharmacokinetics (PK), and dose proportionality of a novel apomorphine hydrochloride oromucosal solution, as well as its relative bioavailability to subcutaneous apomorphine injection and apomorphine sublingual film. In part A of the study, 12 patients with PD received 2 mg oromucosal apomorphine (4% weight/volume) and 2 mg subcutaneous apomorphine in a randomized order, followed by 4 and 8 mg oromucosal apomorphine. In part B of the study, 13 patients with PD received 7 mg oromucosal apomorphine (7% weight/volume) and 30 mg sublingual apomorphine in a randomized order, followed by 14 mg oromucosal apomorphine. Washout between dose administrations in both study parts was at least 2 days. Safety, tolerability, and PK were assessed pre- and post-dose. Both study parts showed that oromucosal apomorphine was generally well-tolerated. Observed side effects were typical for apomorphine administration and included asymptomatic orthostatic hypotension, yawning, fatigue, and somnolence. Oromucosal apomorphine exposure increased with dose, although less than dose proportional. The mean (SD) maximum exposure reached with 14 mg oromucosal apomorphine was 753.0 (298.6) ng*min/mL (area under the plasma concentration-time curve from zero to infinity) and 8.0 (3.3) ng/mL (maximum plasma concentration). This was comparable to exposure reached after 2 mg subcutaneous apomorphine and approximately half of the exposure observed with 30 mg sublingual apomorphine. In summary, clinically relevant plasma concentrations could be reached in PD patients without tolerability issues.

Metabolite profiling of foslevodopa/foscarbidopa in plasma of healthy human participants by LC-HRMS indicates no major differences compared to administration of levodopa/carbidopa intestinal gel

Analysis was conducted to compare levodopa/carbidopa pharmacokinetics and drug-related material in plasma of healthy participants after receiving a continuous infusion of Levodopa/Carbidopa Intestinal Gel (LCIG) to a continuous subcutaneous infusion of foslevodopa/foscarbidopa. Study samples were from a randomized, open-label, 2-period crossover study in 20 healthy participants. Participants received either 24-h foslevodopa/foscarbidopa SC infusion to the abdomen or LCIG delivered for 24 h to the jejunum through a nasogastric tube with jejunal extension. Serial blood samples were collected for PK. Comparability of the LD PK parameters between the two treatment regimens was determined. Selected plasma samples were pooled per treatment group and per time point for metabolite profiling. LC-MSn was performed using high-resolution mass spectrometry to identify drug-related material across the dosing regimens and time points. The LD PK parameter central values and 90% confidence intervals following the foslevodopa/foscarbidopa subcutaneous infusion were between 0.8 and 1.25 relative to the LCIG infusion. With LCIG administration, LD, CD, 3-OMD, DHPA, DOPAC, and vanillacetic acid were identified in plasma at early and late time points (0.75 and 24 h); the metabolic profile after administration of foslevodopa/foscarbidopa demonstrated the same drug-related compounds with the exception of the administered foslevodopa. 3-OMD and vanillacetic acid levels increased over time in both treatment regimens. Relative quantification of LC-MS peak areas showed no major differences in the metabolite profiles. These results indicate that neither the addition of monophosphate prodrug moieties nor SC administration affects the circulating metabolite profile of foslevodopa/foscarbidopa compared to LCIG.

Pharmacokinetics and multi-peak phenomenon analysis of novel anti-Parkinson's drug FLZ after multi-dose in cynomolgus monkeys

The novel anti-Parkinson disease drug, FLZ, had a complicated drug absorption and metabolise process reported in single-dose studies. A multi-peak absorption peak phenomenon was found.This study focused on the multi-dose pharmacokinetics (PK) characteristics of FLZ, T1, and T2 in cynomolgus monkeys and raised discussion on its multi-peak absorption situation. Different doses of FLZ ranging from 75 to 300 mg/kg were administered orally to 16 cynomolgus monkeys. The whole treatment period lasted for 42 days with FLZ once a day.The primary metabolites of FLZ were Target1 (T1) and Target2 (T2), which had plasma exposure (calculated as AUC0-24, day 42) approximately 2 and 10 times higher than the parent drug. The proportion of plasma exposure increase was lower than the proportion of dose increase in FLZ, T1, and T2.Gender influenced its exposure (AUC0-24) with approximately 3-fold higher in males than females. There was no significant accumulation of T1 and T2. Enterohepatic Circulation (EHC) and gastrointestinal (GI) tract absorption may be involved in the mechanism of multi-peak characteristics.

A neoteric annotation on the advances in combination therapy for Parkinson's disease: nanocarrier-based combination approach and future anticipation. Part II: nanocarrier design and development in focus

INTRODUCTION

The current treatment modalities available for Parkinson's disease (PD) prove inadequate due to the inherent constraints in effectively transporting bioactive compounds across the blood-brain barrier. The utilization of synergistic combinations of multiple drugs in conjunction with advanced nanotechnology, emerges as a promising avenue for the treatment of PD, offering potential breakthroughs in treatment efficacy, targeted therapy, and personalized medicine.

AREAS COVERED

This review provides a comprehensive analysis of the efficacy of multifactorial interventions for PD, simultaneously addressing the primary challenges of conventional therapies and highlighting how advanced technologies can help overcome these limitations. Part II focuses on the effectiveness of nanotechnology for improving pharmacokinetics of conventional therapies, through the synergistic use of dual or multiple therapeutic agents into a single nanoformulation. Significant emphasis is laid on the advancements toward innovative integrations, such as CRISPR/Cas9 with neuroprotective agents and stem cells, all effectively synergized with nanocarriers.

EXPERT OPINION

By using drug combinations, we can leverage their combined effects to enhance treatment efficacy and mitigate side effects through lower dosages. This article is meant to give nanocarrier-mediated co-delivery of drugs and the strategic incorporation of CRISPR/Cas9, either as an independent intervention or synergized with a neuroprotective agent.

Fasting state is one of the factors associated with plasma levodopa fluctuations during levodopa‒carbidopa intestinal gel treatment

INTRODUCTION

Some patients with Parkinson's disease (PD) undergoing levodopa‒carbidopa intestinal gel (LCIG) treatment experience motor fluctuations in the afternoon. The migrating motor complex, a specific periodic migrating contraction pattern occurring in the stomach and small intestine during the fasting state, can affect drug absorption. We aimed to compare the pharmacokinetic parameters between two conditions (with and without lunch) and assessed the influence of the fasting state on the levodopa pharmacokinetics in LCIG treatment.

METHODS

We evaluated the levodopa pharmacokinetics from 12:00 p.m. to 6:00 p.m. in 10 LCIG-treated PD patients in the presence and absence of lunch.

RESULTS

The maintenance dose of LCIG correlated strongly with the mean plasma concentration of levodopa in the absence (r = 0.94, coefficient of determination (R²) = 0.89, p < 0.001) or presence of lunch (r = 0.96, R² = 0.93, p < 0.001). Comparison of the pharmacokinetic parameters revealed that the coefficient of variation was significantly greater in the condition without lunch than in the condition with lunch (p = 0.004): 16.73% (4.88%) without lunch and 9.22% (3.80%) with lunch. There were no significant differences in the mean plasma concentration of levodopa (p = 0.49) and area under the plasma concentration‒time curve (p = 0.27) between the two conditions.

CONCLUSIONS

Plasma concentrations of levodopa fluctuated more in patients undergoing LCIG treatment without than with lunch. Our results indicate that a small amount of food intake may be a better corrective approach for worsening of symptoms in the fasting state rather than additional levodopa.

Identification of anti-Parkinson's Disease Lead Compounds from Aspergillus ochraceus Targeting Adenosin Receptors A2A

Two novel alkaloids compounds together with fifteen know metabolites were identified from Aspergillus ochraceus. The stereochemistry features of the new molecules were determined via HRESIMS, NMR, ECD, and XRD analyses. Amongst these, compounds two compounds exhibited potential efficacy as anti-Parkinson's disease with the EC50 values of 2.30 and 2.45 μM, respectively. ADMET prediction showed that these compounds owned favorable drug-like characteristics and safe toxicity scores towards CNS drugs. Virtual screening analyses manifested that the compounds exhibited not only robust and reliable interactions to adenosine receptors A2A , but also higher binding selectivity to A2A receptors than to A1 and A3 receptors. Molecular dynamics simulation demonstrated the reliability of molecular docking results and the stability of the complexes obtained with the novel compounds and A2A receptors in natural environments. It is the first time that anti-PD lead compounds have been identified from Aspergillus ochraceus and targeting adenosine A2A receptors.

In vitro investigations on dopamine loaded Solid Lipid Nanoparticles

The progressive degeneration of nigrostriatal neurons leads to depletion of the neurotransmitter dopamine (DA) in Parkinson's disease (PD). The hydrophilicity of DA, hindering its cross of the Blood Brain Barrier, makes impossible its therapeutic administration. This work aims at investigating some physicochemical features of novel Solid Lipid Nanoparticles (SLN) intended to enhance DA brain delivery for PD patients by intranasal administration. For this aim, novel SLN were formulated in the presence of Glycol Chitosan (GCS), and it was found that SLN containing GCS and DA were smaller than DA-loaded SLN, endowed with a slightly positive zeta potential value and, remarkably, incorporated 81 % of the initial DA content. The formulated SLN were accurately characterized by Infrared Spectroscopy in Attenuated Total Reflectance mode (FT-IT/ATR) and Thermogravimetric Analysis (TGA) to highlight SLN solid-state properties as a preliminary step forward biological assay. Overall, in vitro characterization shows that SLN are promising for DA incorporation and stable from a thermal viewpoint. Further studies are in due course to test their potential for PD treatment.

Pharmacokinetics of ADS-5102 (Amantadine) Extended Release Capsules Administered Once Daily at Bedtime for the Treatment of Dyskinesia

BACKGROUND

Preclinical and clinical studies suggest amantadine immediate-release (IR) may reduce dyskinesia in Parkinson's disease (PD), although higher doses are associated with increased CNS adverse events (AEs). ADS-5102 is an extended release amantadine capsule formulation, designed for once-daily dosing at bedtime (qhs) to provide high concentrations upon waking and throughout the day, with lower concentrations in the evening. The pharmacokinetics (PK) of ADS-5102 were assessed in two phase I studies in healthy subjects, and a blinded, randomized phase II/III dose-finding study in PD patients.

METHODS

The first phase I study assessed single ADS-5102 doses (68.5, 137, and 274 mg) in a crossover design, whereas the second phase I study evaluated ADS-5102 137 mg for 7 days followed by amantadine IR 81 mg twice daily (or reverse order). In the phase II/III double-blind study, PD patients with dyskinesia were randomized to ADS-5102 (210, 274, or 338 mg) or placebo for 8 weeks.

RESULTS

Single ADS-5102 doses resulted in a slow initial rise in amantadine plasma concentration, with delayed time to maximum concentration (12-16 h). Amantadine plasma concentrations were higher in PD patients versus healthy volunteers. The steady-state profile of once-daily ADS-5102 was significantly different from that of twice-daily amantadine IR, such that the two formulations are not bioequivalent. PK modeling suggested the recommended daily ADS-5102 dosage (274 mg qhs) resulted in 1.4- to 2.0-fold higher amantadine plasma concentrations during the day versus amantadine IR.

CONCLUSIONS

ADS-5102 can be administered once-daily qhs to achieve high amantadine plasma concentrations in the morning and throughout the day, when symptoms of dyskinesia occur.

Pharmacokinetics and Bioequivalence of Memantine Tablet and a New Dry Syrup Formulation in Healthy Japanese Males: Two Single-Dose Crossover Studies

Introduction

Memantine hydrochloride, an N-methyl-D-aspartate receptor antagonist, is used to treat Alzheimer’s disease (AD). A new dry syrup formulation containing memantine hydrochloride has been developed to improve medication adherence in AD patients and to reduce family and caregiver burden. This study was conducted to assess the bioequivalence of this new formulation to the tablet.

Methods

Two single-dose, randomized, open-label, two-period, two-group, crossover studies were conducted to assess the bioequivalence of a test product [dry syrup, 2%, 1 g (containing 20 mg of memantine hydrochloride)] to a reference product (film-coated tablet) under two dosing conditions: administration of the test product as a suspension in water (Study I) and as granules taken with water (Study II). Blood samples were collected at specified time intervals, and memantine plasma concentrations were determined using a validated liquid chromatography tandem mass spectrometry method. The pharmacokinetic parameters of memantine were calculated using non-compartmental analysis. The maximum concentration (C_max) and area under the concentration–time curve up to the last sampling time (AUC_all) were used to assess the bioequivalence of the two formulations.

Results

The geometric least square mean (GLSM) ratios [90% confidence interval (CI)] of the C_max and AUC_all of memantine for the test product to the reference product were 0.981 (0.943–1.020) and 0.978 (0.955–1.001) in Study I, and 0.973 (0.944–1.003) and 1.004 (0.983–1.025) in Study II, respectively. In both studies, the 90% CI values of the GLSM ratios of C_max and AUC_all were within the prespecified bioequivalence range (0.80–1.25). The safety of the test product under both dosing conditions and that of the reference product were not different.

Conclusions

The new dry syrup formulation containing memantine hydrochloride showed bioequivalence to the film-coated tablet under the two dosing conditions. Thus, the new dry syrup is suitable under either dosing condition for patients with AD.

Funding

Daiichi Sankyo Co., Ltd.

Levodopa-carbidopa intestinal gel high concentration formulation is clinically bioequivalent to commercial formulation

A new levodopa-carbidopa intestinal gel (LCIG) system featuring a higher levodopa/carbidopa (LD/CD) concentration and viscosity, LCIG-HV, is being developed to reduce the intrajejunal volume of LD/CD that is administered as compared to the current commercial formulation, LCIG-LV. This study characterizes the LCIG-HV formulation and compares it to the LCIG-LV formulation via dissolution testing and a clinical pharmacokinetic bioequivalence study. In vitro release profiles of LD/CD were determined using a USP Dissolution Apparatus 2 with 500 mL of phosphate buffer (pH 4.5) operating at 25 RPM. A single dose, open-label study was conducted according to a two-period, randomized, crossover design in 28 healthy subjects. The point estimate (PE) of the levodopa Cmax geometric mean for the LCIG-HV formulation was 4% higher than that of the LCIG-LV formulation. PEs of levodopa AUCt and AUCinf geometric means were comparable for both formulations. PEs of carbidopa Cmax , AUCt and AUCinf geometric means for the LCIG-HV formulation were 3%-5% higher than those of the LCIG-LV formulation. For both formulations, the median Tmax for levodopa was 1.0 and 3.0 hours for carbidopa. The levodopa half-life harmonic mean was 1.6 hour for both formulations. The carbidopa half-life harmonic mean was 1.9 and 2.0 hour, respectively, for the LCIG-HV and LCIG-LV formulations. Cmax , AUCt and AUCinf of LD/CD carbidopa were comparable for both formulations. The current study demonstrates that the LCIG-LV and LCIG-HV formulations are clinically bioequivalent for LD/CD according to FDA guidance. However, the dissolution method was over discriminatory of formulation differences.

Simultaneous determination of FLZ and its metabolite (M1) in human plasma and urine by UHPLC-MS/MS: Application to a pharmacokinetic study

FLZ is a novel anti-Parkinson's disease candidate drug. The main active metabolite is FLZ O-dealkylation (M1) in preclinical studies. A reliable ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) quantitation method was developed for the simultaneous determination of FLZ and M1 with low limits of quantitation in human plasma (0.1 ng/mL) and urine (0.5 ng/mL). The plasma and urine samples were both purified by full-automatic solid phase extraction (SPE) method with ensured high extraction recovery and little matrix effect for both analytes, and then separated on a BEH C₁₈ column (2.1 × 50 mm, 1.7 μm). Detection and quantification were performed using an electrospray ionization (ESI) source in positive mode by multiple reaction monitoring (MRM). The precursor to product ion transitions were monitored at m/z 450.3⁺→313.2⁺ for FLZ, m/z 436.3⁺→299.1⁺ for M1, m/z 462.6⁺→142.0⁺ for [D₁₂]-FLZ (internal standard of FLZ) and m/z 447.2⁺→125.2⁺ for [D₁₁]-M1 (internal standard of M1), respectively. This method showed good linearity, accuracy, precision and stability in the range of 0.1-100 ng/mL in plasma and 0.5-500 ng/mL in urine of two analytes. Finally, the developed method was successfully applied to a pharmacokinetic research in Chinese healthy volunteers after oral administration of FLZ tablets.

inPentasomes: An innovative nose-to-brain pentamidine delivery blunts MPTP parkinsonism in mice

Preclinical and clinical evidences have demonstrated that astroglial-derived S100B protein is a key element in neuroinflammation underlying the pathogenesis of Parkinson's disease (PD), so much as that S100B inhibitors have been proposed as promising candidates for PD targeted therapy. Pentamidine, an old-developed antiprotozoal drug, currently used for pneumocystis carinii is one of the most potent inhibitors of S100B activity, but despite this effect, is limited by its low capability to cross blood brain barrier (BBB). To overcome this problem, we developed a non-invasive intranasal delivery system, chitosan coated niosomes with entrapped pentamidine (inPentasomes), in the attempt to provide a novel pharmacological approach to ameliorate parkinsonism induced by subchronic MPTP administration in C57BL-6 J mice. inPentasomes, prepared by evaporation method was administered daily by intranasal route in subchronic MPTP-intoxicated rodents and resulted in a dose-dependent manner (0.001-0.004 mg/kg) capable for a significant Tyrosine Hydroxylase (TH) positive neuronal density rescue in both striatum and substantia nigra of parkinsonian mice. In parallel, inPentasomes significantly decreased the extent of glial-related neuroinflammation through the reduction of specific gliotic markers (Iba-1, GFAP, COX-2, iNOS) with consequent PGE₂ and NO₂^- release reduction, in nigrostriatal system. inPentasomes-mediated S100B inhibition resulted in a RAGE/NF-κB pathway downstream inhibition in the nigrostriatal circuit, causing a marked amelioration of motor performances in intoxicated mice. On the basis of our results, chitosan coated niosomes loaded with pentamidine, the inPentasome system, self-candidates as a promising new intranasal approach to mitigate parkinsonism in humans and possibly paves the way for a possible clinical repositioning of pentamidine as anti-PD drug.

[Outpatient establishment and initial management of treatment with intraduodenal levodopa-carbidopa infusion in advanced Parkinson's disease]

INTRODUCTION

Treatment with intraduodenal levodopa-carbidopa infusion is one of the three therapies currently available for advanced Parkinson's disease. It optimizes the benefit of antiparkinsonian treatment by counteracting the negative effect of erratic gastric emptying on the absorption of oral levodopa. The purpose is to describe our outpatient protocol of treatment establishment.

PATIENTS AND METHODS

In our unit we have implemented a protocol for the treatment with intradoudenal levodopa-carbidopa infusion without admission based on the development of a multidisciplinary circuit among the Neurology Service, the Digestive Endoscopy Unit and the Home Hospitalization Unit.

RESULTS

Over one and a half year, we treated five patients with advanced Parkinson's disease. All of them remain on the medication and no significant side effect has taken place.

CONCLUSION

The outpatient onset install of this treatment saves costs and avoids the negative impact of admission on the patient with advanced Parkinson's disease, in the same way that favors their adaptation and tolerability to it.

Impact of Neurodegenerative Diseases on Drug Binding to Brain Tissues: From Animal Models to Human Samples

Drug efficacy in the central nervous system (CNS) requires an additional step after crossing the blood-brain barrier. Therapeutic agents must reach their targets in the brain to modulate them; thus, the free drug concentration hypothesis is a key parameter for in vivo pharmacology. Here, we report the impact of neurodegeneration (Alzheimer's disease (AD) and Parkinson's disease (PD) compared with healthy controls) on the binding of 10 known drugs to postmortem brain tissues from animal models and humans. Unbound drug fractions, for some drugs, are significantly different between healthy and injured brain tissues (AD or PD). In addition, drugs binding to brain tissues from AD and PD animal models do not always recapitulate their binding to the corresponding human injured brain tissues. These results reveal potentially relevant implications for CNS drug discovery.

Repositioning of Omarigliptin as a once-weekly intranasal Anti-parkinsonian Agent

Drug repositioning is a revolution breakthrough of drug discovery that presents outstanding privilege with already safer agents by scanning the existing candidates as therapeutic switching or repurposing for marketed drugs. Sitagliptin, vildagliptin, saxagliptin & linagliptin showed antioxidant and neurorestorative effects in previous studies linked to DPP-4 inhibition. Literature showed that gliptins did not cross the blood brain barrier (BBB) while omarigliptin was the first gliptin that crossed it successfully in the present work. LC-MS/MS determination of once-weekly anti-diabetic DPP-4 inhibitors; omarigliptin & trelagliptin in plasma and brain tissue was employed after 2 h of oral administration to rats. The brain/plasma concentration ratio was used to deduce the penetration power through the BBB. Results showed that only omarigliptin crossed the BBB due to its low molecular weight & lipophilic properties suggesting its repositioning as antiparkinsonian agent. The results of BBB crossing will be of interest for researchers interested in Parkinson's disease. A novel intranasal formulation was developed using sodium lauryl sulphate surfactant to solubilize the lipophilic omarigliptin with penetration enhancing & antimicrobial properties. Intranasal administration showed enhanced brain/plasma ratio by 3.3 folds compared to the oral group accompanied with 2.6 folds increase in brain glucagon-like peptide-1 concentration compared to the control group.

Discovery of indolylpiperazinylpyrimidines with dual-target profiles at adenosine A2A and dopamine D2 receptors for Parkinson's disease treatment

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive loss of dopaminergic neurons in the substantia nigra of the human brain, leading to depletion of dopamine production. Dopamine replacement therapy remains the mainstay for attenuation of PD symptoms. Nonetheless, the potential benefit of current pharmacotherapies is mostly limited by adverse side effects, such as drug-induced dyskinesia, motor fluctuations and psychosis. Non-dopaminergic receptors, such as human A2A adenosine receptors, have emerged as important therapeutic targets in potentiating therapeutic effects and reducing the unwanted side effects. In this study, new chemical entities targeting both human A2A adenosine receptor and dopamine D2 receptor were designed and evaluated. Two computational methods, namely support vector machine (SVM) models and Tanimoto similarity-based clustering analysis, were integrated for the identification of compounds containing indole-piperazine-pyrimidine (IPP) scaffold. Subsequent synthesis and testing resulted in compounds 5 and 6, which acted as human A2A adenosine receptor binders in the radioligand competition assay (Ki = 8.7-11.2 μM) as well as human dopamine D2 receptor binders in the artificial cell membrane assay (EC50 = 22.5-40.2 μM). Moreover, compound 5 showed improvement in movement and mitigation of the loss of dopaminergic neurons in Drosophila models of PD. Furthermore, in vitro toxicity studies on compounds 5 and 6 did not reveal any mutagenicity (up to 100 μM), hepatotoxicity (up to 30 μM) or cardiotoxicity (up to 30 μM).

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.

A randomized, double-blind, placebo-controlled trial of camicinal in Parkinson's disease

Background: Delayed gastric emptying may impair l‐dopa absorption, contributing to motor fluctuations. We evaluated the effect of camicinal (GSK962040), a gastroprokinetic, on the absorption of l‐dopa and symptoms of PD.

Methods: Phase II, double‐blind, placebo‐controlled trial. Participants were randomized to receive camicinal 50 mg once‐daily (n = 38) or placebo (n = 20) for 7 to 9 days.

Results:l‐dopa exposure was similar with coadministration of camicinal compared to placebo. Median time to maximum l‐dopa concentration was reduced, indicating more rapid absorption of l‐dopa. Camicinal resulted in significant reduction in OFF time (–2.31 hours; 95% confidence interval: –3.71, –0.90), significant increase in ON time (+1.88 hours; 95% confidence interval: 0.28, 3.48) per day, and significant decrease in mean total MDS‐UPDRS score (–12.5; 95% confidence interval: –19.67, ‐5.29). Camicinal treatment was generally well tolerated.

Conclusions: PD symptom improvement with camicinal occurred in parallel with more rapid absorption of l‐dopa. This study provides evidence of an improvement of the motor response to l‐dopa in people with PD treated with camicinal 50 mg once‐daily compared with placebo, which will require further evaluation. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Effect of opicapone multiple-dose regimens on levodopa pharmacokinetics

AIMS

To compare the levodopa/carbidopa (LC) and levodopa/benserazide (LB) pharmacokinetic profiles following repeated doses of opicapone (OPC) administered apart from levodopa.

METHODS

Two randomized, double blind, sex-balanced, placebo-controlled studies in four groups of 12 or 18 healthy subjects each. In each group, enrolled subjects received a once-daily morning (5, 15 and 30 mg) or evening (5, 15 and 50 mg) administration of OPC or placebo for up to 28 days. On the morning of Day 11, 12 h after the OPC or placebo evening dose, or the morning of Day 21, 1 h after the OPC or placebo dose, a single dose of immediate-release 100/25 mg LC was administered. Similarly, on Day 18 morning, 12 h after the OPC or placebo evening dose, or Day 28 morning, 1 h after the OPC or placebo dose, a single dose of immediate-release 100/25 mg LB was administered.

RESULTS

All OPC treatments, in relation to the placebo group, presented a higher extent of exposure (AUC) to levodopa following either LC or LB doses. A relevant but not dose-dependent increase in the levodopa AUC occurred with all OPC dose groups in relation to placebo. All active treatments significantly inhibited both peak (Emax ) and extent (AUEC) of the catechol-O-methyltransferase activity in relation to placebo. The tolerability profile was favourable.

CONCLUSION

Opicapone, as once-daily oral evening regimen and/or 1 h apart from levodopa therapy, increases the bioavailability of levodopa associated with its pronounced, long-lasting and sustained catechol-O-methyltransferase inhibition. The tolerability profile was favourable and similar between OPC and placebo.

Zonisamide suppresses endoplasmic reticulum stress-induced neuronal cell damage in vitro and in vivo

Zonisamide has been reported to have protective effects on epilepsy and Parkinson׳s disease and to work via various mechanisms of action, such as inhibition of monoamine oxidase-B and enhancement of tyrosine hydroxylase. Recently, it has been suggested that zonisamide itself shows neuroprotective actions. Therefore, in the present study we investigated the neuroprotective effects of zonisamide against endoplasmic reticulum (ER) stress. We used human neuroblastoma (SH-SY5Y) cells and investigated the protective effects of zonisamide against tunicamycin- and thapsigargin-induced neuronal cell death. In addition, we investigated the effect of zonisamide against 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell death and the mechanism of protection against ER stress. In vivo, we investigated the effect of zonisamide (20 mg/kg, p.o.) in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson׳s disease. Zonisamide not only suppressed MPP⁺-induced cell death, but also inhibited ER stress-induced cell death and suppressed the expression of ER stress-related factors such as C/EBO homologous protein (CHOP) in vivo. Furthermore, zonisamide inhibited the activation of caspase-3 in vitro. These results suggest that zonisamide affected ER stress via caspase-3. We think that ER stress, particularly the mechanism via caspase-3, is involved in part of the neuroprotective effect of zonisamide against the experimental models of Parkinson׳s disease.

Helicobacter pylori infection and drugs malabsorption

Drug absorption represents an important factor affecting the efficacy of oral drug treatment. Gastric secretion and motility seem to be critical for drug absorption. A causal relationship between impaired absorption of orally administered drugs and Helicobacter pylori (H. pylori) infection has been proposed. Associations have been reported between poor bioavailability of l-thyroxine and l-dopa and H. pylori infection. According to the Maastricht Florence Consensus Report on the management of H. pylori infection, H. pylori treatment improves the bioavailability of both these drugs, whereas the direct clinical benefits to patients still await to be established. Less strong seems the association between H. pylori infection and other drugs malabsorption, such as delavirdine and ketoconazole. The exact mechanisms forming the basis of the relationship between H. pylori infection and impaired drugs absorption and/or bioavailability are not fully elucidated. H. pylori infection may trigger a chronic inflammation of the gastric mucosa, and impaired gastric acid secretion often follows. The reduction of acid secretion closely relates with the wideness and the severity of the damage and may affect drug absorption. This minireview focuses on the evidence of H. pylori infection associated with impaired drug absorption.

The effect of nanoemulsion as a carrier of hydrophilic compound for transdermal delivery

The purpose of the present study was to investigate the effect of nanoemulsions as a carrier vehicle of hydrophilic drug for transdermal delivery. The response surface methodology with a mixture design was used to evaluate the effect of ingredient levels of nanoemulsion formulations including cosurfactant (isopropyl alcohol, 20 ∼ 30%), surfactant (mixed of Brij 30 and Brij 35, 20 ∼ 30%), and distilled-water (34.5 ∼ 50.0%) on properties of the drug-loaded nanoemulsions including physicochemical characters and drug permeability through rat skin. The result showed that the hydrophilic drug in aqueous solution with or without penetration enhancer could not transport across rat skin after 12 h of application. Used nanoemulsions as carrier vehicle, the permeation rate of drug was significantly increased from 0 to 63.23 µg/cm2/h and the lag time was shortened from more than 12 h to about 2.7 ∼ 4.0 h. Moreover, the drug-loaded nanoemulsion formulation also showed physicochemical stability after 3 month storage at 25°C and 40°C.

Opicapone: a short lived and very long acting novel catechol-O-methyltransferase inhibitor following multiple dose administration in healthy subjects

AIMS

The aim of this study was to assess the tolerability, pharmacokinetics and inhibitory effect on erythrocyte soluble catechol-O-methyltransferase (S-COMT) activity following repeated doses of opicapone.

METHODS

This randomized, placebo-controlled, double-blind study enrolled healthy male subjects who received either once daily placebo or opicapone 5, 10, 20 or 30 mg for 8 days.

RESULTS

Opicapone was well tolerated. Its systemic exposure increased in an approximately dose-proportional manner with an apparent terminal half-life of 1.0 to 1.4 h. Sulphation was the main metabolic pathway. Opicapone metabolites recovered in urine accounted for less than 3% of the amount of opicapone administered suggesting that bile is likely the main route of excretion. Maximum S-COMT inhibition (Emax ) ranged from 69.9% to 98.0% following the last dose of opicapone. The opicapone-induced S-COMT inhibition showed a half-life in excess of 100 h, which was dose-independent and much longer than plasma drug exposure. Such a half-life translates into a putative underlying rate constant that is comparable with the estimated dissociation rate constant of the COMT-opicapone complex.

CONCLUSION

Despite its short elimination half-life, opicapone markedly and sustainably inhibited erythrocyte S-COMT activity making it suitable for a once daily regimen.

Therapeutic response to pramipexole in a patient with multiple system atrophy with predominant parkinsonism: positron emission tomography and pharmacokinetic assessments

Multiple system atrophy with predominant parkinsonism (MSA-P) usually shows poor responsiveness to dopaminergic medications. We herein describe a patient with MSA-P who exhibited a good response to pramipexole but not to an ordinary dose of L-dopa. Positron emission tomography (PET) displayed severely impaired presynaptic dopaminergic availability and relatively preserved postsynaptic D2 receptor binding capacity. The pharmacokinetic analyses demonstrated relatively low bioavailability for L-dopa and adequate plasma levels of pramipexole, even at baseline, on a stable daily dose. The PET features and pharmacokinetic differences between L-dopa and pramipexole indicate the presence of unique therapeutic responses to dopaminergic medications in the patient.

[Corneal toxicity due to amantadine]

CASE REPORT

A 64 year-old female with Parkinson disease treated with amantadine for two years who suddenly suffered bilateral corneal oedema. It was initially treated as herpetic endotheliitis without improvement as we lacked information on her chronic treatment. The corneal oedema finally resolved after withdrawing the drug.

DISCUSSION

Amantadine hydrochloride may produce endothelial dysfunction. Once the amantadine treatment is stopped, the corneal oedema may be reversible but endothelial density remains low. An ophthalmologist examination should be performed before the initiation of amantadine treatment in order to establish a risk: benefit ratio, especially in those patients with low endothelial density or any endothelial anomaly.

Continuous intestinal infusion of levodopa/carbidopa in advanced Parkinson's disease: efficacy, safety and patient selection

Long-term oral therapy with levodopa is associated with the development of motor fluctuations and dyskinesia in a large percentage of patients with Parkinson's disease (PD). Motor complications are associated with a number of non-motor symptoms and have a negative impact on disability and quality of life. There are three therapeutic options available for the management of patients at this advanced stage: high frequency deep brain stimulation, continuous subcutaneous infusion of apomorphine, and continuous intestinal infusion of levodopa/carbidopa. On the basis of published data and in consideration of the risk-benefit profile of current therapeutic strategies, we here propose an algorithm to help clinicians select the most suitable treatment option for patients with advanced PD.

[Treatment of apomorphine infusion adverse effects: subcutaneous nodules and neuropsychiatric complications]

Subcutaneous nodules and neuropsychiatric complications are the most relevant adverse effects during apomorphine infusion treatment. Subcutaneous nodules appear in almost all the patients and accurate information and training of both patient and caregiver is essential to minimise their impact on the treatment. Although neuropsychiatric complications are not more frequent than with other dopaminergic treatments, they are linked with increasing difficulty of treatment and worsening of patient's quality of life.

Helicobacter pylori eradication for Parkinson's disease

BACKGROUND

Levodopa is the mainstay of treatment for alleviating the motor symptoms associated with Parkinson's disease. However, patients often experience fluctuations in their symptoms over time and 'wearing off' which may be partly related to variable absorption of the drug. There is some evidence that treatment of the common gastrointestinal infection Helicobacter pylori (H pylori) with antibiotics may improve levodopa absorption in the gut and hence improve symptoms.

OBJECTIVES

1) What is the prevalence of H pylori in Parkinson's disease patients? 2) Does treatment of H pylori infection with antibiotics improve symptoms in Parkinson's disease patients? Is this effect dependent on improvements in the absorption of levodopa?

SEARCH METHODS

We searched electronic databases (including CENTRAL, MEDLINE, EMBASE, PsycINFO and CINAHL) and trial registers, handsearched conference proceedings and carried out citation searching on key articles. All searching was updated in August 2009. We contacted authors to provide additional information where necessary.

SELECTION CRITERIA

Clinical trials in patients with a well-defined definition of Parkinson's disease and who were H pylori-positive. Two people independently selected studies for inclusion using predetermined criteria. We used recruitment figures from clinical trials and other studies identified from the searching to determine the prevalence of H pylori in Parkinson's disease.

DATA COLLECTION AND ANALYSIS

Two authors abstracted data from the source papers and assessed methodological quality independently. We presented results descriptively.

MAIN RESULTS

Two completed and one ongoing clinical trial met the inclusion criteria. One trial (34 patients randomised) examined the effects of H pylori eradication on levodopa absorption and motor symptoms and found significant improvements in both. The ongoing trial has similar objectives and aims to recruit 100 patients. The other completed trial (20 patients analysed) sought to find a causal link between infection with H pylori and Parkinsonism and was non-contributory. A worsening of symptoms was noted with eradication failure.The prevalence of H pylori in Parkinson's disease was reported in four studies and ranged from 37% to 59% which is similar to that of the general population.

AUTHORS' CONCLUSIONS

There is currently a lack of evidence on the effects of screening and treating H pylori in patients with Parkinson's disease. There is limited evidence to suggest that H Pylori eradication improves the absorption of levodopa and improves motor symptoms. Results from an ongoing trial will inform the evidence base and will be incorporated in an update of this review. There is a need for well-conducted randomised controlled trials with standard outcome measures for motor symptoms and incorporating the costs of screening and treatment.

The effect of different dosing regimens of levodopa/carbidopa/entacapone on plasma levodopa concentrations

BACKGROUND

Repeated dosing of levodopa/carbidopa/entacapone (LCE) has shown a favourable pharmacokinetic (PK) profile compared with levodopa/carbidopa (LC), but increases maximum plasma levodopa concentrations (C(max)) during the day. High levodopa concentrations are associated with peak-dose dyskinesias.

PURPOSE

To determine whether administering LCE 75/18.5/200 and 125/31.5/200 mg (LCE 75 and LCE 125) following a morning dose of LCE 100/25/200 and 150/37.5/200 mg (LCE 100 and LCE 150), respectively, would avoid the increase in levodopa C(max) values observed during multiple dosing of LCE 100 and LCE 150.

METHODS

This was an open, randomized, three-period, crossover PK trial in healthy volunteers (n = 19). Subjects were randomized to Group 1 or 2. Group 1 received in random sequence: LCE 150 followed by LCE 125 three times daily (tid); LCE 150 four times daily (qid); LC 150 qid. Group 2 received in random sequence: LCE 100 followed by LCE 75 tid; LCE 100 qid; LC 100 qid. Levodopa C(max), minimum plasma concentration (C(min)), area under the curve (AUC(0-14)) and peak-trough fluctuation (PTF) were calculated up to 14 h after the first dose.

RESULTS

Levodopa C(max) was not increased when the LCE dose was decreased by 25 mg after the morning dose. In comparison to LC, levodopa C(min) levels and AUC(0-14) values for LCE were significantly higher, while the levodopa PTF was significantly smaller.

CONCLUSIONS

Reducing the dose of LCE by 25 mg following the first morning dose results in a more consistent levodopa C(max) profile, avoiding levodopa accumulation while maintaining significantly higher C(min) levels and AUC(0-14) values compared with LC.

Relationship between 3-O-methyldopa and the clinical effects of entacapone in advanced Parkinson's disease

The aim of this study is to clarify the relationship between serum 3-O-methyldopa (3-OMD) and the clinical effects of entacapone. The 3-OMD and maximum serum concentration (Cmax) of levodopa were measured in 21 Parkinson's Disease patients who took 100 mg levodopa / dopa decarboxylase inhibitor. After the administration of entacapone, the 3-OMD concentration and percentage of "on" time during waking hours (% of "on" time) were studied for 8 weeks. The 3-OMD concentration was reduced by 34%, and the increase in % of "on" time was 28% at the 8th week compared with baseline. We defined the COMT-index as [baseline 3-OMD concentration] / [levodopa Cmax when 100 mg levodopa was administered alone]. The COMT-index was significantly correlated with the increase in % of "on" time at the 8th week. In conclusion, the measurement of baseline 3-OMD and levodopa pharmacokinetics is useful for predicting the clinical effects of entacapone.

Myths and realities of continuous dopaminergic stimulation

Motor fluctuations and dyskinesia in later stages of Parkinson's disease (PD) are caused by pharmacokinetic as well as pharmacodynamic factors, intermittent dopaminergic stimulation being one of the most important. In the healthy brain, dopamine neurons in the substantia nigra pars compacta fire tonically at a steady rate of about 4 cycles/second. In later stages of PD, steady firing is replaced by pulsatile stimulation which causes molecular and physiologic changes in the basal ganglia. Continuous dopaminergic stimulation has been shown to dramatically improve motor fluctuations and dyskinesia by modifications of oral treatment (dopamine agonists, smaller, more frequent levodopa doses, controlled-release formulation of levodopa, addition of agents that slow down the catabolism of dopamine, such as inhibitors of catechol-O-methyl transferase and monoamine oxidase), transdermal delivery (rotigotine), infusion therapies (intravenous levodopa, subcutaneous application of apomorphine and lisuride, duodenal infusion of levodopa) and deep brain stimulation of the subthalamic nucleus.

[Pharmacokinetics of hemantane in rats]

The pharmacokinetics ofhemantane after administration in different ways has been studied in rats. It is established that hemantane introduced both orally (p.o.) and intravenously (i.v.) is very intensively metabolized, with the main metabolites characterized by m/z = 250 and 266 and detected for 6 hours after the administration in both ways. Hemantane shows high rate of permeability into its target organ--brain--whereas the permeation of its metabolites is extremely low. The absolute bioavailability ofhemantane upon p.o. administration was 14.1%. The substance is subject to the "first-pass effect". The unchanged substance was determined in daily urine and feces in very small fractions of the administered dose: 0.23% in urine and 0.08% in feces after i.v. administration and 0.02% in feces after p.o. administration. Thus, it may be concluded that the substance is completely absorbed in rats from the gastro-intestinal tract into systemic blood circulation.

[The effect of Stalevo-dosing on quality of life of Parkinsonian patients with wearing-off]

In Stalevo tablets, used in the therapy of patients with Parkinson's disease, levodopa is combined with decarboxylase inhibitors and COMT inhibitors to provide a more steady plasma concentration of levodopa. Previously several study has shown, that the better pharmacokinetic profile decreases the fluctuation of motor and non-motor symptoms. Better control of symptoms improves quality of life. Ideal blood levels of levodopa however can only be achieved by multiple daily dosing. This may be uncomfortable, may decrease compliance, thereby influence quality of life. To evaluate this, an observational follow-up study was undertaken in Hungary in 2007, among patients who were given Stalevo - independently of this study - because of signs of decrease in the duration of drug effect (wearing off). Patients got Stalevo in three, four or five daily divided dosages, the results were assesed after three months. The study included 223 patients (ITT population), of whom 208 (PP population) responded regarding quality of life on both visits. Statistical analysis of the results showed that treatment significantly decreased symptoms of wearing off (wearing off card with 19 items) and improved quality of life (EQ-5D and VAS quality of life scale) regardless of the frequency of dosing.

Pharmacokinetics of a once-daily extended-release formulation of pramipexole in healthy male volunteers: three studies

BACKGROUND

Pramipexole is a dopamine agonist used in the treatment of Parkinson's disease. The currently available immediate-release (IR) formulation is taken orally 3 times daily.

OBJECTIVES

These studies were conducted to evaluate the pharmacokinetic properties of a variety of prototypes for a once-daily extended-release (ER) formulation of pramipexole and to further characterize the prototype whose pharmacokinetics best matched those of the IR formulation.

METHODS

Three Phase I studies were conducted, all in healthy adult men aged <or=50 years with a body mass index of 18.5 to 29.9 kg/m(2). In the first study, 7 prototypes of a once-daily ER formulation with various release properties, including rate and pH dependence, were compared with the IR formulation taken 3 times daily to identify the optimal pharmacokinetic resemblance based on predefined criteria derived from plasma AUC(0-24h), C(max), and C(min). In the second study, a level A in vitro/in vivo correlation (IVIVC) suitable for predicting an entire in vivo bioavailability time course based on in vitro dissolution was established and validated, and the single-dose pharmacokinetics of the optimal ER formulation identified in the first study were analyzed for food effect. In the third study, steady-state pharmacokinetics of the optimal ER formulation were assessed across a range of pramipexole doses (0.375-4.5 mg/d), including investigation of the food effect at steady state for the highest dose. Tolerability was assessed throughout all studies based on physical examinations, laboratory measurements, and adverse events (AEs).

RESULTS

The 3 studies included 18, 15, and 39 subjects, respectively. Among the ER prototypes tested at 0.75 mg once daily in study 1, a matrix tablet had the optimal pharmacokinetic resemblance to IR pramipexole 0.25 mg TID, with a geometric mean AUC(0-24h,ss) of 17.4 ng.h/mL (vs 16.0 ng.h/mL for the IR formulation), C(max,ss) of 0.967 ng/mL (vs 1.09 ng/mL), and C(min,ss) of 0.455 ng/mL (vs 0.383 ng/mL). For single-dose ER 0.375 mg administered in the fasted state in study 2, in vivo bioavailability was predictable from in vitro dissolution data, with internal mean absolute percent prediction errors of 3.18% for AUC(0-30h) and 4.87% for C(max), and external mean absolute prediction errors of 6.61% and 3.34%, respectively, satisfying current guidelines for a level A IVIVC. For single-dose ER 0.375 mg administered in the fed state, the upper bound of the 90% CI for fed:fasted values was 119.8 for AUC(0-30h) (within the bioequivalence limits of 80%-125%) and 134.1 for C(max). At steady state in study 3 (subjects' 5th treatment day), dosing at 0.375 to 4.5 mg in the fasted state was associated with a linear, dose-proportional increase in pharmacokinetic parameters, including AUC(0-24h,ss) and C(max,ss). At the highest fasted dose (4.5 mg), the geometric coefficient of variation for interindividual variability at steady state was 30.1% for AUC(0-24h,ss) (vs 21.4% for IR pramipexole 1.5 mg TID) and 22.3% for C(max,ss) (vs 19.0%). At steady state, the upper bounds of the 90% CIs for fed:fasted values with ER 4.5 mg were 122.1 for AUC(0-24h) and 126.8 for C(max). No serious AEs occurred, and the dropout rate was low.

CONCLUSIONS

In these studies in healthy male volunteers, an ER pramipexole formulation was identified that resembled the IR formulation in terms of both pharmacokinetics and tolerability. In patients with Parkinson's disease, once-daily use of an ER formulation may improve the convenience of treatment relative to the IR formulation taken 3 times daily and thus increase compliance.

[Optimisation of treatment of Parkinson's disease with levodopa]

This article presents the major strategies for individualisation and optimisation of levodopa therapy. The relationship between pharmacokinetic and pharmacodynamic effects of levodopa is discussed. Pharmacokinetic parameters in different stages of Parkinson's disease are interpreted. Moreover, the main differences in pharmacokinetics of levodopa formulations and routes of administration are presented. The authors also suggest methods to increase efficacy and safety of levodopa therapy in patients with Parkinson's disease.

Glutamate-conjugated liposomes of dopamine hydrochloride for effective management of parkinsonism's

The blood-brain barrier restricts the brain uptake of many important hydrophilic drugs and limits their efficacy in the treatment of brain diseases because of the presence of tight junctions, high metabolic capacity, low pinocytic vesicular traffic, and efficient efflux mechanisms. In the present project, amino acid-coupled liposomes bearing dopamine HCl were prepared to deliver the drug to the brain utilizing receptor-mediated transcytosis. Uncoupled liposomes were prepared by cast film method using phosphatidylcholine and cholesterol, whereas coupled liposomes were prepared using phosphatidylcholine, cholesterol, and glutamate stearylamine conjugate in the film. These liposomes were characterized for entrapment efficiency, vesicle size, shape, in vitro drug release, and in vivo studies. The in vitro drug release was analysed by using dialysis membrane. The vesicle size was found to increase upon coupling of liposomes, whereas percent entrapment efficiency was reduced from 38.89 +/- 1.94% to 34.15 +/- 1.70% after coupling of liposomes. The in vitro percent cumulative drug release studies exhibited 51.6% drug release for uncoupled liposome and 37.9% for coupled liposome at the end of 24 h. These selected formulations were subjected for in vivo performance, which was assessed by periodic measurement of drug (chlorpromazine)-induced catatonia in albino rats (Wistar strain) and fluorescence microscopy studies of the rat brain. The results were compared with plain dopamine HCl solution. Studies revealed that dopamine HCl can be effectively delivered to brain via glutamate-coupled liposomes, and results clearly indicated the superiority of the coupled liposomal formulation over the uncoupled formulation.

Design, biometric simulation and optimization of a nano-enabled scaffold device for enhanced delivery of dopamine to the brain

This study focused on the design, biometric simulation and optimization of an intracranial nano-enabled scaffold device (NESD) for the site-specific delivery of dopamine (DA) as a strategy to minimize the peripheral side-effects of conventional forms of Parkinson's disease therapy. The NESD was modulated through biometric simulation and computational prototyping to produce a binary crosslinked alginate scaffold embedding stable DA-loaded cellulose acetate phthalate (CAP) nanoparticles optimized in accordance with Box-Behnken statistical designs. The physicomechanical properties of the NESD were characterized and in vitro and in vivo release studies performed. Prototyping predicted a 3D NESD model with enhanced internal micro-architecture. SEM and TEM revealed spherical, uniform and non-aggregated DA-loaded nanoparticles with the presence of CAP (FTIR bands at 1070, 1242 and 2926 cm(-1)). An optimum nanoparticle size of 197 nm (PdI=0.03), a zeta potential of -34.00 mV and a DEE of 63% was obtained. The secondary crosslinker BaCl(2) imparted crystallinity resulting in significant thermal shifts between native CAP (T(g)=160-170 degrees C; T(m)=192 degrees C) and CAP nanoparticles (T(g)=260 degrees C; T(m)=268 degrees C). DA release displayed an initial lag phase of 24 h and peaked after 3 days, maintaining favorable CSF (10 microg/mL) versus systemic concentrations (1-2 microg/mL) over 30 days and above the inherent baseline concentration of DA (1 microg/mL) following implantation in the parenchyma of the frontal lobe of the Sprague-Dawley rat model. The strategy of coupling polymeric scaffold science and nanotechnology enhanced the site-specific delivery of DA from the NESD.

[Severe kyphosis and esophagus hiatal hernia affected in the levodopa absorption of a patient with Parkinson's disease]

An 82 year-old woman with Parkinson's disease complained of a tendency to fall. She has had an extensive kyphosis since she was 66 years old. Over the last 6 months, she has repeatedly fallen. Even though she took anti-parkisonian drugs, she had also developed camptocormia. Her plasma levodopa concentration was analyzed for 4 hrs after administrating an oral dose of levodopa (200 mg) plus carbidopa (20 mg) at the time of fasting. The change in the plasma levodopa concentration showed bimodal peaks. The physical symptoms depended on the plasma concentration and improved twice. Esophageal tortuosity and esophageal hiatal hernia were detected by esophagography and upper gastric endoscopy. Such physical symptoms were speculated to have been caused by the transit disturbance of the drug in the gastrointestinal duct. During a second analysis of the plasma levodopa concentration, the patient was instructed to keep extending her back after consuming the same dose of drugs but with a greater amount of water than in the first analysis. A single and a higher peak were observed for the plasma levodopa concentration, and the physical symptoms, including camptocormia and parkinsonism, were improved. Hunched posture could influence the absorption of antiparkinsonian drugs.

Genetic polymorphism of catechol O-methyltransferase and pharmacokinetics of levodopa in healthy Chinese subjects

We studied the distribution of catechol O-methyltransferase (COMT) genotypes in the Chinese Fujian Han population and explored the potential effect of COMT genetic polymorphism on the pharmacokinetics of levodopa. Polymerase chain reaction (PCR) was employed in the COMT genotype analysis of 166 volunteers. After a single oral dose of levodopa/benserazide, the plasma concentration of levodopa was determined by high-performance liquid chromatography (HPLC) with electrochemical detection (ECD). In the 166 subjects, the frequencies of G/G, G/A and A/A COMT genotypes were 58.4%, 36.7% and 4.9%, respectively. The frequency of the homozygous A/A genotype was much lower than in caucasians and Southwest Asians. COMT activity of erythrocytes in the G/A genotype group was significantly lower than in the G/G genotype group but significantly higher than in the A/A genotype group. There was no significant difference in pharmacokinetic parameters, including t(1/2alpha), t(1/2beta), AUC(0-infinity), CL/F, C(max), t(max) and V/F. The frequency of COMT genotypes in the Chinese Fujian Han population, which is related to COMT enzyme activity, is significantly different from that in caucasians and Southwest Asians. The pharmacokinetic characteristics of levodopa in healthy Chinese subjects may not be dependent on their COMT genotype status. From the 166 volunteers, 5 G/G, 5 G/A and 4 A/A genotype male subjects were recruited for the study of levodopa pharmacokinetics.

Development and application of a high-performance liquid chromatographic method for the determination of in vitro drug release of levodopa, carbidopa, and entacapone from a tablet formulation

A simple, precise, and accurate high-performance liquid chromatographic method was developed and validated to determine percent drug release of levodopa (LEV), carbidopa (CAR), and entacapone (ENT) from its combination dosage form. A mixture of acetonitrile and buffer was used as the mobile phase for reversed-phase liquid chromatographic separation for determination of the in vitro drug release of LEV, CAR, and ENT. A dissolution test was conducted at 75 rpm with United States Pharmacopeia (USP) apparatus-II (paddle) by using pH 5.5 phosphate buffer as a dissolution medium. Three formulations, differing in strength, were evaluated. The developed method was validated for specificity, linearity, precision, accuracy, and solution stability. The specificity of the method was determined in the presence of placebo interference. The method was linear over the drug concentration ranges of 4-210 microg/mL for LEV, 1-52 microg/mL for CAR, and 6-280 microg/mL for ENT. Precision was established by determination of system precision, method precision, and intermediate precision. Accuracy values for the method ranged from 96.8 to 104.3% for LEV, from 97.2 to 101.3% for CAR, and from 99.5 to 102.8% for ENT. The developed method was suitable for estimating percent drug release of LEV, CAR, and ENT in terms of the dissolution test.

Evolution of the bioavailability and other pharmacokinetic parameters of levodopa (with carbidopa) in rabbits

Levodopa pharmacokinetics show important inter- and intraindividual differences when it is administered by the oral route. As a result of fluctuating drug plasma concentrations, patients may develop motor fluctuations and dyskinesias. Therefore, it is important to perform studies on levodopa pharmacokinetics in the same individual. The aim of this study was to contribute to a better knowledge of the evolution of the pharmacokinetics of levodopa administered with carbidopa. The study involved the oral administration of 20/5 mg/kg levodopa/carbidopa to rabbits for two different time periods (7 or 14 days), due to the fact that inhibition of aromatic L-amino-acid decarboxylase by carbidopa is not immediate. After 7 days of treatment, the levodopa AUC increased by 12.6% from day 1 (range: 114.2-150.7 microg.min/ml) to day 7 (range: 131.1-166.0 microg.min/ml) and C(max) increased by 9.6% (range: 1.90-2.86 microg/ml on day 1 and 2.12-3.13 microg/ml on day 7). After 14 days of treatment, the increase in AUC was 17.0% (range: 119.6-160.1 microg.min/ml on day 1 and 142.9-172.7 microg.min/ml on day 14) and C(max) increased by 6.5% (range: 2.29-2.96 microg/ml on day 1 and 2.41-3.07 microg/ml on day 14). The values obtained for C(min) (sample obtained immediately before levodopa/carbidopa administration) in both groups increased progressively with the duration of the treatment. C(max) and AUC values were very similar after 7 or 14 days of treatment. The time needed for C(min) stabilization was slightly higher, because we found significant differences until day 11 of treatment.

Rasagiline: a review of its use in the management of Parkinson's disease

Rasagiline (Azilect) is a novel, selective, irreversible second-generation inhibitor of monoamine oxidase type B (MAO-B). It is administered orally once daily and is approved in the US, Canada, Mexico, Israel and the EU for use as monotherapy and as adjunct therapy in the treatment of Parkinson's disease. Results of well designed clinical studies indicate that rasagiline is effective as initial monotherapy and improves Parkinson's symptomatology in patients with early Parkinson's disease. In addition, when administered in conjunction with levodopa, in patients with moderate to advanced disease and motor fluctuations, rasagiline reduces mean daily 'off' time and increases daily 'on' time without troublesome dyskinesias, compared with controls. Rasagiline is generally well tolerated as monotherapy and adjunctive therapy and is administered once daily. Thus, rasagiline, administered as a simple and convenient dosage regimen, is a well tolerated and effective option for monotherapy in patients with early Parkinson's disease and for adjunctive therapy in patients with moderate to advanced disease.