Frequent administration of levodopa/carbidopa microtablets vs levodopa/carbidopa/entacapone in healthy volunteers

Reduced Plasma Levodopa Fluctuations with More Frequent Administration of a Novel Carbidopa/Levodopa Functionally Scored Tablet

Levodopa/carbidopa remains the gold standard for treating Parkinson disease (PD), but chronic pulsatile administration contributes to motor complications. This Phase 1 study used a new immediate-release (IR) formulation of carbidopa/levodopa 25/100 mg that is functionally scored for easy and precise splitting to evaluate the effects on levodopa plasma variability when smaller doses are taken more frequently. These functionally scored tablets were shown to be bioequivalent to carbidopa/levodopa 25-/100-mg IR generic reference tablets. Twenty-two healthy volunteers received a whole tablet every 4 hours versus half of the tablet every 2 hours. Plasma levodopa fluctuations were significantly reduced with half-tablets dosed every 2 hours, with a 44% reduction in peaks (P < .0001). While drug exposure did not differ, parameters that underlie motor response variations, including mean peak-to-trough difference and variance, were 51% and 56% less, respectively, with more frequent dosing (both P ≤ .0024). Safety and tolerability of both regimens were similar. In conclusion, more frequent administration of half-tablets of the new functionally scored IR formulation safely provided more constant levodopa levels than whole tablets dosed less often. This tablet technology could facilitate the benefits of more physiologic dopamine replenishment in patients with PD, particularly those with reduced manual dexterity.

Optimizing levodopa therapy, when and how? Perspectives on the importance of delivery and the potential for an early combination approach

INTRODUCTION

There is currently a resurgence of levodopa as the initial treatment of choice for most patients with Parkinson's disease, albeit at lower doses than previously used. The addition of adjuvant treatments (including MAO-B inhibitors, COMT inhibitors and dopamine agonists) is an established strategy to reduce motor complications that develop with sustained levodopa therapy.

AREAS COVERED

In this narrative review, the authors discuss the evidence underpinning current levodopa optimization strategies, during early disease and once motor complications occur. To support the discussion, the authors performed a broad PubMed search with the terms 'levodopa/L-dopa/L-Dopa, and Parkinson's disease,' restricted to clinical trials. There is now a wealth of evidence that improving levodopa delivery to the brain improves outcomes and we discuss how agents can be combined earlier in the course of disease to leverage the full potential of this strategy.

EXPERT OPINION

Levodopa remains the cornerstone of antiparkinsonian therapy. Several promising advances in formulation have been made and include novel extended-release oral drugs as well as non-oral delivery systems. However, evidence has long suggested that anti-parkinsonian medications may be better used in combination earlier in the disease, and consequently patients will benefit from low doses of several agents rather than ever larger levodopa doses.

Personalized Medicine Approach in Treating Parkinson's Disease, Using Oral Administration of Levodopa/Carbidopa Microtablets in Clinical Practice

Background: The most effective symptomatic treatment in Parkinson’s disease (PD) is levodopa in standard doses. However, as the disease progresses, there may be a need for a more personalized approach and fine tuning, in accordance with the patients’ needs. This study aims to evaluate the individual experience of levodopa/carbidopa 5/1.25 mg microtablets (LC-5) in clinical practice with respect to efficacy, tolerability, and usability. The method used was as follows: patients answered a questionnaire concerning the effect and usability of LC-5, and their medical records were reviewed. Regarding results, thirty-five survey responses were obtained, and 29 patients’ medical records were reviewed. The LC-5 dose dispenser usability was generally rated positively and facilitated medication adherence. The majority (85%) of patients reported symptom improvement while using LC-5, compared with previous standard treatments. These results suggest that LC-5 therapy is generally well-tolerated, with favorable patient-reported efficacy and user friendliness, as well as the possibility for an individualized, fine-tuned PD treatment. Further studies with a prospective design and larger study population are needed to confirm the results.

Emerging Pharmacotherapies for Motor Symptoms in Parkinson's Disease

Parkinson's disease (PD) is the second commonest neurodegenerative disorder in the older adult and is characterized by progressive disabling motor symptoms of bradykinesia, tremor, rigidity, postural instability and also non motor symptoms that affect quality of life. The pharmacotherapy of PD consists of oral, transdermal, and subcutaneous medications, as well as invasive advanced therapies at later stages of the disease. PD medications are often started as monotherapy but with the progression of the illness often there is a need to add more medications and frequently comprises of a challenging polypharmacotherapy. Adverse effects of pharmacotherapy often add to the problems of adequate treatment. Patients and physicians have to prioritize treatment goals on the most disabling symptoms and the safest and most effective treatments. Almost every year newer medications and modes of delivery continue to be researched and added to the therapeutic armamentarium. This review article outlines existing and emerging pharmacotherapies for motor symptoms in PD.

Improving the Delivery of Levodopa in Parkinson's Disease: A Review of Approved and Emerging Therapies

Levodopa is the most effective drug for the treatment of Parkinson's disease, but its use as an oral medication is complicated by its erratic absorption, extensive metabolism and short plasma half-life. On long-term use and with disease progression, there is a high incidence of motor and non-motor complications, which remain a major clinical and research challenge. It is widely accepted that levodopa needs to be administered using formulations that result in good and consistent bioavailability and the physiologically relevant and continuous formation of dopamine in the brain to maximise its efficacy while avoiding and reversing 'wearing off' and dyskinesia. However, the physicochemical properties of levodopa along with its pharmacokinetic and pharmacodynamic profile make it difficult to deliver the drug in a manner that fulfils these criteria. In this review, we examine the problems associated with the administration of levodopa in Parkinson's disease and how the use of novel technologies and delivery devices is leading to a more consistent and sustained levodopa delivery with the aim of controlling motor function as well as non-motor symptoms.

[New Therapeutic Options for the Individualised Titration of Levodopa]

Levodopa is the most effective medication in the treatment of Parkinson's disease. In the course of the disease the storage facility of dopaminergic neurones deteriorates, so that the duration of the half-life period likewise converges. This results in fluctuations in performance, and also in dyskinesias as a further consequence of the narrowing therapeutic window. Therapeutically, this in turn leads to further fractioning of the levodopa dosage and a reduction of single-dose levels. There is, however, only limited scope for doing this with the conventional levodopa formulations. For this reason, the introduction of water-soluble microtablets à 5 / 1.25 mg levodopa / carbidopa can be regarded as a beneficial extension permitting for fine titration of the dopaminergic stimulation. Here we present this new therapeutic principle, the available data and concepts for clinical use.

Pharmacokinetics of Rytary®, An Extended-Release Capsule Formulation of Carbidopa-Levodopa

Parkinson's disease (PD) is a chronic progressive neurological disorder characterized by resting tremor, rigidity, bradykinesia, gait disturbance, and postural instability. Levodopa, the precursor to dopamine, coadministered with carbidopa or benserazide, aromatic amino acid decarboxylase inhibitors, is the most effective and widely used therapeutic agent in the treatment of PD. With continued levodopa treatment, a majority of patients develop motor complications such as dyskinesia and motor 'on-off' fluctuations, which are, in part, related to the fluctuations in plasma concentrations of levodopa. A new extended-release (ER) carbidopa-levodopa capsule product (also referred to as IPX066) was developed and approved in the US as Rytary^® and in the EU as Numient^®. The capsule formulation is designed to provide an initial rapid absorption of levodopa comparable to immediate-release (IR) carbidopa-levodopa, and to subsequently provide stable levodopa concentrations with reduced peak-to-trough excursions in plasma concentrations in order to reduce motor fluctuations associated with pulsatile stimulation of dopamine receptors and to minimize dyskinesia. Phase III studies of this ER carbidopa-levodopa capsule formulation in patients with PD have shown a significant reduction in 'off' time compared with IR carbidopa-levodopa and carbidopa-levodopa-entacapone. We present a review of the clinical pharmacokinetics and pharmacodynamics of this ER product of carbidopa-levodopa in healthy subjects and in patients with PD.

Population pharmacokinetics of levodopa/carbidopa microtablets in healthy subjects and Parkinson's disease patients

OBJECTIVES

Low dose, dispersible, levodopa/carbidopa microtablets with an automatic dose dispenser have been developed to facilitate individualized levodopa treatment. The aim of this study was to characterize the pharmacokinetics (PK) of levodopa and carbidopa after microtablet administration, and evaluate the impact of potential covariates.

METHODS

The population PK analysis involved data from 18 healthy subjects and 18 Parkinson's disease patients included in two single-dose, open-label levodopa/carbidopa microtablet studies. The analysis was carried out using non-linear mixed effects modeling. Bodyweight was included on all disposition parameters according to allometric scaling. Potential influence of additional covariates was investigated using graphical evaluation and adjusted adaptive least absolute shrinkage and selection operator.

RESULTS

Dispositions of levodopa and carbidopa were best described by a two- and one-compartment model respectively. Double-peak profiles were described using two parallel absorption compartments. Levodopa apparent clearance was found to decrease with increasing carbidopa dose (15% lower with 75 compared to 50 mg of carbidopa) and disease stage (by 18% for Hoehn and Yahr 1 to 4). Carbidopa apparent clearance was found to decrease with age (28% between the age of 60 and 80 years). An external evaluation showed the model to be able to reasonably well predict levodopa concentrations following multiple-dose microtablet administration in healthy subjects.

CONCLUSIONS

The presented models adequately described the PK of levodopa and carbidopa, following microtablet administration. The developed model may in the future be combined with a pharmacokinetic-pharmacodynamic target and used for individualized dose selection, utilizing the flexibility offered by the microtablets.

Individualization of levodopa treatment using a microtablet dispenser and ambulatory accelerometry

AIM

This 4-week open-label observational study describes the effect of introducing a microtablet dose dispenser and adjusting doses based on objective free-living motor symptom monitoring in individuals with Parkinson's disease (PD).

METHODS

Twenty-eight outpatients with PD on stable levodopa treatment with dose intervals of ≤4 hour had their daytime doses of levodopa replaced with levodopa/carbidopa microtablets, 5/1.25 mg (LC-5) delivered from a dose dispenser device with programmable reminders. After 2 weeks, doses were adjusted based on ambulatory accelerometry and clinical monitoring.

RESULTS

Twenty-four participants completed the study per protocol. The daily levodopa dose was increased by 15% (112 mg, P < 0.001) from period 1 to 2, and the dose interval was reduced by 12% (22 minutes, P = 0.003). The treatment adherence to LC-5 was high in both periods. The MDS-UPDRS parts II and III, disease-specific quality of life (PDQ-8), wearing-off symptoms (WOQ-19), and nonmotor symptoms (NMS Quest) improved after dose titration, but the generic quality-of-life measure EQ-5D-5L did not. Blinded expert evaluation of accelerometry results demonstrated improvement in 60% of subjects and worsening in 25%.

CONCLUSIONS

The introduction of a levodopa microtablet dispenser and accelerometry aided dose adjustments improve PD symptoms and quality of life in the short term.

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.

First clinical experience with levodopa/carbidopa microtablets in Parkinson's disease

BACKGROUND

Levodopa is the most effective symptomatic treatment throughout the course of Parkinson's disease, but as the disease progresses, there may be a need for individualized, fine-tuned treatments.

AIM

To evaluate individualized levodopa/carbidopa dosing using microtablets dispensed with a dose dispenser, with respect to efficacy and usability as perceived by patients.

METHODS

Patient records and dose dispenser reports from patients previously or currently treated with microtablets and a dose dispenser were reviewed, and a patient questionnaire concerning effect and usability was sent to patients.

RESULTS

Eleven patient records, four dose dispenser reports and nine survey responses were obtained. The treatment effect was considered to be improved by six of nine patients. One-third found their bradykinesia to be improved, and the non-troublesome dyskinesia was unchanged according to a majority of patients; however, some experienced the duration and magnitude of troublesome dyskinesia to be worse. The usability was generally rated as good. The four dose dispenser reports obtained showed 97(±5)% total adherence.

CONCLUSIONS

The experienced effect of treatment can, for some patients, be improved by the use of microtablets, and the dose dispenser was considered user-friendly. Further studies with a larger study population and prospective design are needed to confirm the results.

Development of new levodopa treatment strategies in Parkinson's disease-from bedside to bench to bedside

This review will illustrate the process of moving from an idea through preclinical research and Galenic developments into clinical investigations and finally to approval by regulatory agencies within the European Union. The two new treatment strategies described, levodopa/carbidopa intestinal gel and levodopa/carbidopa microtablets, for advanced Parkinson's disease, have been developed in collaborative research within departments at Uppsala University. With this historical approach, reference priority is given to reports considered to be of special importance for this more than two decades long process 'from bedside to bench to bedside'.

Levodopa/carbidopa microtablets in Parkinson's disease: a study of pharmacokinetics and blinded motor assessment

Background

Motor function assessments with rating scales in relation to the pharmacokinetics of levodopa may increase the understanding of how to individualize and fine-tune treatments.

Objectives

This study aimed to investigate the pharmacokinetic profiles of levodopa-carbidopa and the motor function following a single-dose microtablet administration in Parkinson’s disease.

Methods

This was a single-center, open-label, single-dose study in 19 patients experiencing motor fluctuations. Patients received 150% of their individual levodopa equivalent morning dose in levodopa-carbidopa microtablets. Blood samples were collected at pre-specified time points. Patients were video recorded and motor function was assessed with six UPDRS part III motor items, dyskinesia score, and the treatment response scale (TRS), rated by three blinded movement disorder specialists.

Results

AUC_0–4/dose and C_max/dose for levodopa was found to be higher in Parkinson’s disease patients compared with healthy subjects from a previous study, (p = 0.0008 and p = 0.026, respectively). The mean time to maximum improvement in sum of six UPDRS items score was 78 min (±59) (n = 16), and the mean time to TRS score maximum effect was 54 min (±51) (n = 15). Mean time to onset of dyskinesia was 41 min (±38) (n = 13).

Conclusions

In the PD population, following levodopa/carbidopa microtablet administration in fasting state, the C_max and AUC_0–4/dose were found to be higher compared with results from a previous study in young, healthy subjects. A large between subject variability in response and duration of effect was observed, highlighting the importance of a continuous and individual assessment of motor function in order to optimize treatment effect.

Levodopa/carbidopa intestinal gel: an effective formulation for the management of advanced Parkinson's disease

SUMMARY 

With disease progression, almost all Parkinson's disease (PD) patients eventually experience motor fluctuations, often posing a significant challenge for patients and caregivers. Majority of these patients end up with complex medication regimens resulting in increased incidence of adverse effects and a poorer quality of life. Treatment options for advanced PD remain limited; thus, providing the optimal treatment for this growing subpopulation of patients continues to be the focus of many drug development efforts. While deep brain stimulation is considered the most significant therapeutic advancement for advanced PD, it remains an expensive and invasive procedure, with its own risks and complications, which limits global applicability to a wider PD population. Levodopa/carbidopa intestinal gel is one option that may offer a therapeutic benefit as significant as that of deep brain stimulation, and to a broader spectrum of PD patients. This article reviews the pharmacological properties, efficacy, safety and tolerability of levodopa/carbidopa intestinal gel in PD.

Willingness to pay for a new drug delivery in Parkinson patients

Objective

The Swedish reimbursement system operates a system where prices are set based on the expected value to the consumer. This value can be measured using willingness to pay (WTP).

Aim

To assess Parkinson’s disease (PD) patients’ WTP for newly developed microtablets of levodopa in combination with a drug-delivering electronic device (M/E) compared to standard treatment with levodopa in combination with the COMT (catechol-O-methyl transferase)-inhibitor entacapone (L/e).

Method

A total of 2,000 randomly included PD patients had a postal questionnaire covering demographics, disease-specific issues, views on medication and WTP in different hypothetical scenarios. The first scenario was M/E with no change in effects or side effects; the second scenario was M/E with same effect and less side effects; and the third scenario was M/E with improved effect and less side effects. These scenarios were coupled to different costs to choose from.

Results

A total of 999 patients (50%) responded, mean age of 71 years and a mean PD duration of 9 years. Of all respondents, 50% preferred M/E before L/e in scenario one with increasing preference to scenario three. The average monthly WTP among all respondents in scenario one was SEK 230 and SEK 226 in L/e, both with an almost longitudinal doubling up to scenario three. Duration of PD-related symptoms, high education, and high medication intake implied a higher WTP in all scenarios in contrast to age, sex, and extra doses of levodopa.

Conclusion

WTP for M/E increased gradually with high medication intake and education as well as with expected increased reduction of PD symptoms.

Continuous drug delivery in Parkinson's disease

Development of motor and non-motor complications during the course of Parkinson's disease (PD) is a major challenge for therapeutic management. At advanced disease stages, patients frequently fluctuate between PD symptoms-such as bradykinesia-and dyskinesias, in response to fluctuations in drug concentrations. Continuous subcutaneous infusion of the dopamine agonist apomorphine or intestinal infusion of levodopa reduce such fluctuations in both pharmacokinetics and motor function. This is the basis for the concept of continuous drug delivery in PD, and the more theoretical concept of continuous dopaminergic stimulation. These expressions are sometimes used to describe a treatment that is more continuous in its pharmacokinetic profile or that produces more sustained effects, compared with immediate-release levodopa, i.e. not only pump treatments. For example, sustained-release formulations of levodopa or dopamine agonists, transdermal delivery of rotigotine, and addition of catechol-O-methyltransferase inhibitors or monoamine oxidase-B inhibitors have been developed with the aim to provide more continuous drug concentrations, sustained benefits and minimized side effects. Progress has been made, but there are still knowledge gaps regarding how these treatment alternatives can be optimally used. New treatments are currently being developed to provide the continuous drug delivery that is known to successfully alleviate motor and non-motor complications. Hopefully, although not yet proven, these new methods may also prevent or postpone some of the late-stage complications.

Pharmacokinetics of levodopa, carbidopa, and 3-O-methyldopa following 16-hour jejunal infusion of levodopa-carbidopa intestinal gel in advanced Parkinson's disease patients

Motor complications of Parkinson's disease (PD) are a consequence of pulsatile dopaminergic stimulation from standard oral levodopa therapy. Levodopa-carbidopa intestinal gel (LCIG) is infused continuously via an intrajejunal percutaneous gastrostomy tube. This was the first study designed to characterize the full pharmacokinetic profiles of levodopa, carbidopa, and levodopa metabolite, 3-O-methyldopa (3-OMD) with 16-h LCIG infusion. Nineteen advanced PD patients (mean age, 65 years) who were on LCIG therapy for ≥30 days were enrolled. Patients received their individualized LCIG infusion doses, and serial pharmacokinetic samples were collected. Eighteen patients completed the study; 19 were assessed for safety. Mean (SD) total levodopa and carbidopa doses were 1,580 (403) and 395 (101) mg, respectively. Mean (SD) C(avg) (μg/mL) were 2.9 (0.84) for levodopa, 17.1 (4.99) for 3-OMD, and 0.22 (0.08) for carbidopa. The degree of fluctuation [defined as (C(max)-C(min))/C(avg)] in levodopa, 3-OMD, and carbidopa plasma concentrations was very low (0.52, 0.21, and 0.96, respectively) during hours 2-16 of infusion. Accordingly, the within-subject coefficients of variation in levodopa, 3-OMD, and carbidopa concentrations were low (13%, 6%, and 19%, respectively). Three patients (16%) reported ≥1 treatment-emergent adverse event; none were considered severe. Continuous intrajejunal LCIG infusion maintained stable plasma levodopa levels over 16 h. Consistent exposure has been shown to reduce motor and nonmotor complications associated with oral medications. LCIG was well tolerated, consistent with previous reports.