The effects of different repeated doses of entacapone on the pharmacokinetics of L-Dopa and on the clinical response to L-Dopa in Parkinson's disease

Optimizing extended-release carbidopa/levodopa in Parkinson disease: Consensus on conversion from standard therapy

Purpose of review:

To help clinicians optimize the conversion of a patient's Parkinson disease pharmacotherapy from immediate-release carbidopa/levodopa (IR CD/LD) to an extended-release formulation (ER CD/LD).

Recent findings:

Eleven movement disorders specialists achieved consensus positions on the modification of trial-based conversion guidelines to suit individual patients in clinical practice.

Summary:

Because the pharmacokinetics of ER CD/LD differ from those of IR CD/LD, modification of dosage and dosing frequency are to be expected. Initial regimens may be based on doubling the patient's preconversion levodopa daily dosage and choosing a division of doses to address the patient's motor complications, e.g., wearing-off (warranting a relatively high ER CD/LD dose, possibly at a lower frequency than for IR CD/LD) or dyskinesia (warranting a relatively low dose, perhaps at an unchanged frequency). Patients should know that the main goal of conversion is a steadier levodopa clinical response, even if dosing frequency is unchanged.

Interventions for fatigue in Parkinson's disease

BACKGROUND

Factors contributing to subjective fatigue in people with idiopathic Parkinson's disease (PD) are not well known. This makes it difficult to manage fatigue effectively in PD.

OBJECTIVES

To evaluate the effects of pharmacological and non-pharmacological interventions, compared to an inactive control intervention, on subjective fatigue in people with PD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); MEDLINE (via PubMed); Ovid EMBASE; EBSCO CINAHL; Ovid PsycINFO; PEDro; and the WHO International Clinical Trials Registry Platform Search Portal up to April 2015. References of included studies and identified review articles were screened for additional studies. There were no restrictions based on language, date of publication or study setting.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that report on subjective fatigue in people with PD.

DATA COLLECTION AND ANALYSIS

Two review authors independently performed study selection, data collection and risk of bias assessments.

MAIN RESULTS

Eleven studies were eligible for this systematic review, with a total of 1817 people. Three studies included only people who experienced clinically relevant fatigue (Fatigue Severity Scale score ≥ 4 out of 7 or Multidimensional Fatigue Inventory total score > 48 out of 100), whereas all other studies did not select participants on the basis of experienced fatigue. Nine studies investigated the effects of medication (i.e. levodopa-carbidopa, memantine, rasagiline, caffeine, methylphenidate, modafinil or doxepin) on subjective fatigue. All studies were placebo controlled. There was insufficient evidence to determine the effect of doxepin on the impact of fatigue on activities in daily life (ADL) or fatigue severity (one study, N = 12, standardised mean difference (SMD) = -1.50, 95% confidence interval (CI) -2.84 to -0.15; low quality evidence). We found high quality evidence that rasagiline reduced or slowed down the progression of physical aspects of fatigue (one study, N = 1176, SMD = -0.27, 95% CI -0.39 to -0.16, I(2) = 0%). None of the other pharmacological interventions affected subjective fatigue in PD. With regard to adverse effects, only levodopa-carbidopa showed an increase for the risk of nausea (one study, N = 361, risk ratio (RR) = 1.85, 95% CI 1.05 to 3.27; high quality evidence). Two studies investigated the effect of exercise on fatigue compared with usual care. We found low quality evidence for the effect of exercise on reducing the impact of fatigue on ADL or fatigue severity (two studies, N = 57, SMD = -0.45, 95% CI -1.21 to 0.32, I(2) = 44%).

AUTHORS' CONCLUSIONS

Based on the current evidence, no clear recommendations for the treatment of subjective fatigue in PD can be provided. Doxepin may reduce the impact of fatigue on ADL and fatigue severity; however, this finding has to be confirmed in high quality studies. Rasagiline may be effective in reducing levels of physical fatigue in PD. No evidence was found for the effectiveness of levodopa-carbidopa, memantine, caffeine, methylphenidate, modafinil or exercise. Studies are needed to investigate the effect of exercise intensity on exercise capacity and subjective fatigue. Future studies should focus on interventions that address the maladaptive behavioural or cognitive aspects of fatigue in people with PD. Characteristics, such as severity and nature of perceived fatigue and underlying mood disorders should be considered to identify responders and non-responders when studying interventions for fatigue. The development of a core-set of self-report fatigue questionnaires with established responsiveness and known minimal important difference values will facilitate the interpretation of change in fatigue scores.

Treatment of advanced Parkinson’s disease

Parkinson's disease is a progressive neurological disorder characterized by tremor, bradykinesia, rigidity, gait and postural instability and a variety of nonmotor symptoms. While these and other motor signs typically improve with levodopa, the so-called axial signs, such as dysarthria, dysphagia, postural instability and freezing, and most nonmotor signs, such as depression, cognitive decline and dysautonomia, usually do not respond satisfactorily to levodopa. Furthermore, the use of levodopa may be limited by the development of motor fluctuations, dyskinesias and other adverse effects. This manuscript reviews the medical management of advanced Parkinson's disease, focusing on the treatment of motor fluctuations and dyskinesias and of nonmotor and nonlevodopa responsive symptoms.

Beneficial effects of natural phenolics on levodopa methylation and oxidative neurodegeneration

Levodopa (L-DOPA) is widely used for symptomatic management in Parkinson's disease. We recently showed that (-)-epigallocatechin-3-gallate, a tea polyphenol, not only inhibits L-DOPA methylation, but also protects against oxidative hippocampal neurodegeneration. In the present study, we sought to determine several other common dietary phenolics, namely, tea catechins [(+)-catechin and (-)-epicatechin] and a representative flavonoid (quercetin), for their ability to modulate L-DOPA methylation and to protect against oxidative hippocampal injury. A combination of in vitro biochemical assays, cell culture-based mechanistic analyses, and in vivo animal models was used. While both tea catechins and quercetin strongly inhibit human liver catechol-O-methyltransferase (COMT)-mediated O-methylation of L-DOPA in vitro, only (+)-catechin exerts a significant inhibition of L-DOPA methylation in both peripheral compartment and striatum in rats. The stronger in vivo effect of (+)-catechin on L-DOPA methylation compared to the other dietary compounds is due to its better bioavailability in vivo. In addition, (+)-catechin strongly reduces glutamate-induced oxidative cytotoxicity in HT22 mouse hippocampal neurons in vitro through inactivation of the nuclear factor-κB signaling pathway. Administration of (+)-catechin also exerts a strong neuroprotective effect in the kainic acid-induced oxidative hippocampal neurodegeneration model in rats. In conclusion, (+)-catechin is a dietary polyphenolic that may have beneficial effects in L-DOPA-based treatment of Parkinson patients by inhibiting L-DOPA methylation plus reducing oxidative neurodegeneration.

Dual beneficial effects of (-)-epigallocatechin-3-gallate on levodopa methylation and hippocampal neurodegeneration: in vitro and in vivo studies

BACKGROUND

A combination of levodopa (L-DOPA) and carbidopa is the most commonly-used treatment for symptom management in Parkinson's disease. Studies have shown that concomitant use of a COMT inhibitor is highly beneficial in controlling the wearing-off phenomenon by improving L-DOPA bioavailability as well as brain entry. The present study sought to determine whether (-)-epigallocatechin-3-gallate (EGCG), a common tea polyphenol, can serve as a naturally-occurring COMT inhibitor that also possesses neuroprotective actions.

METHODOLOGY/PRINCIPAL FINDINGS

Using both in vitro and in vivo models, we investigated the modulating effects of EGCG on L-DOPA methylation as well as on chemically induced oxidative neuronal damage and degeneration. EGCG strongly inhibited human liver COMT-mediated O-methylation of L-DOPA in a concentration-dependent manner in vitro, with an average IC50 of 0.36 microM. Oral administration of EGCG moderately lowered the accumulation of 3-O-methyldopa in the plasma and striatum of rats treated with L-DOPA+carbidopa. In addition, EGCG also reduced glutamate-induced oxidative cytotoxicity in cultured HT22 mouse hippocampal neuronal cells through inactivation of the nuclear factor kappaB-signaling pathway. Under in vivo conditions, administration of EGCG exerted a strong protective effect against kainic acid-induced oxidative neuronal death in the hippocampus of rats.

CONCLUSIONS/SIGNIFICANCE

These observations suggest that oral administration of EGCG may have significant beneficial effects in Parkinson's patients treated with L-DOPA and carbidopa by exerting a modest inhibition of L-DOPA methylation plus a strong neuroprotection against oxidative damage and degeneration.

Evaluation of the efficacy and safety of adjuvant treatment to levodopa therapy in Parkinson s disease patients with motor complications

BACKGROUND

One of the complications of long-term treatment of Parkinson's disease (PD) with levodopa is the development of motor complications. Generally, when motor complications develop, clinicians add in an additional drug (to the levodopa regimen) from one of three other classes of anti-Parkinsonian treatments (dopamine agonists, catechol-O-methyl transferase inhibitors (COMTIs) or monoamine oxidase type B inhibitors (MAOBIs)). However, despite trials having shown that these drugs are beneficial compared to placebo, it remains unclear as to the best way to treat patients experiencing motor complications and whether one class of drug is more effective than another.

OBJECTIVES

This meta-analysis aims to assess more reliably the benefits and risks of the three classes of drugs (dopamine agonists, COMTIs and MAOBIs) currently used as adjuvant treatment to levodopa in PD patients suffering from motor complications. The three drug classes were compared with the aim of determining whether one class of drug provides better symptomatic control than another.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library), MEDLINE, EMBASE, PubMed, LILACS and Web of Science, plus major journals in the field, abstract books, conference proceedings and reference lists of retrieved publications.

SELECTION CRITERIA

Randomised trials comparing an orally administered dopamine agonist, COMTI or MAOBI versus placebo, both on a background of levodopa therapy, in PD patients experiencing motor complications.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data on off-time, levodopa dose, motor complications, side-effects, treatment concordance, clinician-rated disability, mortality, quality of life and health economic data.

MAIN RESULTS

Forty-four eligible trials, involving 8436 participants were identified. Compared to placebo, adjuvant therapy significantly reduced off-time (-1.05 hours/day, 95% confidence interval (CI) -1.19 to -0.90; P<0.00001), the required levodopa dose (-55.65 mg/day, CI -62.67 to -48.62; P<0.00001) and improved UPDRS scores (UPDRS ADL score: -1.31 points, CI -1.62 to -0.99; P<0.00001; UPDRS motor score: -2.84 points, CI -3.36 to -2.32; P<0.00001; UPDRS total score: -3.26 points, CI -4.52 to -2.00; P<0.00001). However, dyskinesia (odds ratio (OR) 2.50, CI 2.21 to 2.84; P<0.00001) and side-effects including constipation (OR 3.19, CI 2.17 to 4.68; P<0.00001), dizziness (OR 1.57, CI 1.30 to 1.90; P<0.00001), dry mouth (OR 2.33, CI 1.22 to 4.47; P=0.01), hallucinations (OR 2.16, CI 1.70 to 2.74; P<0.00001), hypotension (OR 1.47, CI 1.18 to 1.83; P=0.0007), insomnia (OR 1.38, CI 1.09 to 1.74; P=0.007), nausea (OR 1.78, CI 1.53 to 2.07; P<0.00001), somnolence (OR 1.87, CI 1.40 to 2.51; P<0.0001) and vomiting (OR 2.56, CI 1.67 to 3.93; P<0.0001) were all increased with adjuvant therapy.Indirect comparisons of the three drug classes suggested that dopamine agonists were more efficacious in reducing off-time (dopamine agonist: -1.54 hours/day; COMTI: -0.83 hours/day; MAOBI: -0.93 hours/day; test for heterogeneity between drug classes P=0.0003) and levodopa dose (dopamine agonist: -116 mg/day; COMTI: -52 mg/day; MAOBI: -29 mg/day; test for heterogeneity between drug classes P<0.00001). UPDRS scores also improved more with dopamine agonists than with COMTI or MAOBI (UPDRS total scores - dopamine agonist: -10.01 points versus COMTI: -1.46 points versus MAOBI: -2.20 points; test for heterogeneity between drug classes P<0.00001), although more dyskinesia were seen with dopamine agonists (OR 2.70) and COMTI (OR 2.50) than with MAOBI (OR 0.94) (test for heterogeneity between drug classes P=0.009). Although the increase in the overall incidence of side-effects was generally more marked with dopamine agonists (OR 1.52) and COMTI (OR 2.0) than with MAOBI (OR 1.32), heterogeneity between drug classes was only of borderline significance (P=0.07).

AUTHORS' CONCLUSIONS

Compared to placebo, adjuvant therapy reduces off-time, levodopa dose, and improves UPDRS scores in PD patients who develop motor complications on levodopa therapy. However, this is at the expense of increased dyskinesia and numerous other side-effects. Indirect comparisons suggest that dopamine agonist therapy may be more effective than COMTI and MAOBI therapy, which have comparable efficacy. However, as indirect comparisons should be interpreted with caution, direct head-to-head randomised trials assessing the impact of these different drug classes on overall patient-rated quality of life are needed.

The effect of peripheral enzyme inhibitors on levodopa concentrations in blood and CSF

Levodopa combined with a dopa-decarboxylase inhibitor, such as carbidopa, shifts the metabolism to the COMT pathway. Adding the peripheral acting COMT inhibitor entacapone provides improvement for patients with PD suffering from motor fluctuations. We studied the effects of the enzyme inhibitors entacapone and carbidopa on the levodopa concentrations in CSF and in blood. Five PD patients with wearing-off underwent lumbar drainage and intravenous microdialysis. Samples were taken 12 h daily for 3 days. Day 1; intravenous levodopa was given, day 2; additional oral entacapone 200 mg tid, day 3; additional oral entacapone 200 mg tid and carbidopa 25 mg bid. Levodopa in CSF and in dialysates was analysed. The AUC for levodopa increased both in blood and CSF when additional entacapone was given alone and in combination with carbidopa. The C(max) of levodopa in both CSF and blood increased significantly. Additional entacapone to levodopa therapy gives an increase of C(max) in CSF and in blood. The increase is more evident when entacapone is combined with carbidopa.

Medical treatment of Parkinson disease

The cardinal characteristics of Parkinson disease (PD) include resting tremor, rigidity, and bradykinesia. Patients may also develop autonomic dysfunction, cognitive changes, psychiatric symptoms, sensory complaints, and sleep disturbances. The treatment of motor and non-motor symptoms of Parkinson disease is addressed in this article.

Delivery of peptide and protein drugs over the blood-brain barrier

Peptide and protein (P/P) drugs have been identified as showing great promises for the treatment of various neurodegenerative diseases. A major challenge in this regard, however, is the delivery of P/P drugs over the blood-brain barrier (BBB). Intense research over the last 25 years has enabled a better understanding of the cellular and molecular transport mechanisms at the BBB, and several strategies for enhanced P/P drug delivery over the BBB have been developed and tested in preclinical and clinical-experimental research. Among them, technology-based approaches (comprising functionalized nanocarriers and liposomes) and pharmacological strategies (such as the use of carrier systems and chimeric peptide technology) appear to be the most promising ones. This review combines a comprehensive overview on the current understanding of the transport mechanisms at the BBB with promising selected strategies published so far that can be applied to facilitate enhanced P/P drug delivery over the BBB.

Medical management of levodopa-associated motor complications in patients with Parkinson's disease

Parkinson's disease is a neurodegenerative disorder that affects approximately 1% of people over the age of 60 years. Levodopa is standard, and often initial, therapy for patients with this condition; however, with continued treatment and as the disease progresses, up to 80% of patients experience 'wearing-off' symptoms, dyskinesias and other motor complications. These levodopa-associated problems may become disabling and profoundly affect quality of life. Medications commonly used to manage these symptoms include monoamine oxidase type B (MAO-B) inhibitors, catechol-O-methyltransferase (COMT) inhibitors, the NMDA receptor antagonist amantadine and dopamine receptor agonists. Agents that block MAO-B, such as rasagiline and selegiline, are used as both initial and adjunctive therapy in patients with Parkinson's disease. These medications increase concentrations of dopamine in the brain by blocking its reuptake from the synaptic cleft, a mechanism that can slow motor decline, increase 'on' time and improve symptoms of Parkinson's disease. Adverse events with these agents can include confusion, hallucination and orthostatic hypotension. MAO-B inhibition may elicit drug-drug interactions if administered with TCAs, SSRIs or SNRIs. Conventional oral selegiline is associated with potentially harmful plasma concentrations of three major amphetamine metabolites, although metabolite concentrations are significantly lower with a new orally disintegrating tablet (ODT) selegiline formulation. Selegiline ODT is also absorbed more efficiently and shows less pharmacokinetic variability than conventional oral selegiline.COMT mediates peripheral catabolism of levodopa. Therefore, agents that block COMT, such as tolcapone and entacapone, increase the elimination half-life of levodopa. Given adjunctively with levodopa, COMT inhibitors can decrease 'off' time and increase 'on' time, as well as lower the daily levodopa dose. Although more potent than entacapone, tolcapone requires monitoring for hepatotoxicity. Amantadine is a noncompetitive NMDA receptor antagonist shown to lower dyskinesia scores and improve motor complications in patients with Parkinson's disease when given adjunctively with levodopa. Dopamine agonists, also used as initial and adjunctive therapy in Parkinson's disease, improve motor response and decrease 'off' time purportedly through direct stimulation of dopamine receptors. Current dopamine agonists include bromocriptine, pergolide, cabergoline, lisuride, apomorphine, pramipexole, ropinirole and rotigotine. Although effective, this class of medications can be associated with cardiovascular and psychiatric adverse effects that can limit their utility. All medications used to manage levodopa-associated motor complications in patients with Parkinson's disease have had differing degrees of success. Although head-to-head comparisons of drugs within classes are rare, some differences have emerged related to effects on motor fluctuations, dyskinesias and on/off times, as well as to adverse effects. When choosing a drug to treat levodopa-induced complications, it is important to consider the risks and benefits of the different classes and of the specific agents within each class, given the different efficacy and safety profiles of each.

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

Pharmacotherapy for Parkinson's disease is focused on dopaminergic drugs, mainly the dopamine precursor levodopa and dopamine receptor agonists. The elimination half-life (t(1/2)) of levodopa from plasma (in combination with a decarboxylase inhibitor) of about 1.5 hours becomes more influential as the disease progresses. The long-duration of response to levodopa, which is evident in early Parkinson's disease, diminishes and after a few years of treatment motor performance is closely correlated to the fluctuating plasma concentrations of levodopa. Absorption of levodopa in the proximal small intestine depends on gastric emptying, which is erratic and may be slowed in Parkinson's disease. The effects of levodopa on motor function are dependent on gastric emptying in patients in the advanced stages of disease. The current treatment concept is continuous dopaminergic stimulation (CDS). Sustained-release formulations of levodopa may provide more stable plasma concentrations. Oral liquid formulations shorten the time to reach peak concentration and onset of effect but do not affect plasma levodopa variability. The t(1/2) of levodopa can be prolonged by adding a catechol-O-methyltransferase inhibitor (entacapone or tolcapone), which may reduce fluctuations in plasma concentrations, although both peak and trough concentrations are increased with frequent administration. Intravenous and enteral (duodenal/jejunal) infusions of levodopa yield stable plasma levodopa concentrations and motor performance. Enteral infusion is feasible on a long-term basis in patients with severe fluctuations. Among the dopamine receptor agonists the ergot derivatives bromocriptine, cabergoline, dihydroergocryptine and pergolide, and the non-ergot derivatives piribedil, pramipexole and ropinirole, have longer t(1/2) compared with levodopa. Thus, they stimulate dopamine receptors in a less pulsatile manner, yet pharmacokinetic studies of repeated doses of dopamine receptor agonists are few. Optimisation of these drugs is often performed with standardised titration schedules. Apomorphine and lisuride have short t(1/2) and are suitable for subcutaneous infusion, with results similar to those of levodopa infusion. Transdermal administration of dopamine receptor agonists such as rotigotine might be an alternative in the future. In general, initial dopamine receptor agonist monotherapy is associated with poorer motor performance and lower incidence of motor complications compared with levodopa. Buccal administration of the monoamine oxidase-B inhibitor selegiline (deprenyl) provides better absorption and less formation of metabolites compared with standard tablets. To conclude, several new drugs, formulations and routes of administration have been introduced in the treatment of Parkinson's disease during the last decade, mainly with CDS as the aim. CDS can be approached by optimising the use of dopaminergic drugs based on pharmacokinetic data.

Human Metabolism of Nebicapone (BIA 3-202), a Novel Catechol-O-Methyltransferase Inhibitor: Characterization of in Vitro Glucuronidation

Nebicapone (BIA 3-202; 1-[3,4-dihydroxy-5-nitrophenyl]-2-phenylethanone), a novel catechol-O-methyltransferase inhibitor, is mainly metabolized by glucuronidation. The purpose of this study was to characterize the major plasma metabolites of nebicapone following p.o. administration of nebicapone to healthy volunteers, and to determine the human UDP-glucuronosyltransferase (UGT) enzymes involved in nebicapone glucuronidation. Plasma samples were collected as part of a clinical trial at different time points postdose and were analyzed for nebicapone and its metabolites using a validated method consisting of a solid-phase extraction, followed by high-performance liquid chromatography/mass spectrometry detection. The primary metabolic pathways of nebicapone in humans involve mainly 3-O-glucuronidation, the major early metabolite, and 3-O-methylation, the predominant late metabolite. Of the nine commercially available recombinant UGT enzymes studied (UGT1A1, UGT1A3, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, and UGT2B15), only UGT1A9 exhibited high nebicapone glucuronosyltransferase specific activity (24.3 +/- 1.3 nmol/mg protein/min). UGT1A6, UGT1A7, UGT1A8, UGT1A10, UGT2B7, and UGT2B15 exhibited low activity (0.1-1.1 nmol/mg protein/min), and UGT1A1 and UGT1A3 showed extremely low activities (less than 0.03 nmol/mg protein/min). The results show that nebicapone is mainly glucuronidated in humans and that multiple UGT enzymes are involved in this reaction.

Present and future drug treatment for Parkinson's disease

Considerable advances made in defining the aetiology, pathogenesis, and pathology of Parkinson's disease (PD) have resulted in the development and rapid expansion of the pharmacopoeia available for treatment. Anticholinergics were used before the introduction of levodopa which is now the drug most commonly used. Dopamine agonists are effective when used alone or as an adjunct to levodopa, while monoamine oxidase B inhibitors improve motor function in early and advanced PD. However, treatment mainly addresses the dopaminergic features of the disease and leaves its progressive course unaffected; the drug treatment available for the management of non-motor symptoms is limited. This article seeks to set current treatment options in context, review emerging and novel drug treatments for PD, and assess the prospects for disease modification. Surgical therapies are not considered.

Early administration of entacapone prevents levodopa-induced motor fluctuations in hemiparkinsonian rats

The purpose of this study was to investigate the effect of the catechol-O-methyltransferase (COMT) inhibitor, entacapone, in the reversal and prevention of "wearing-off" phenomena in hemiparkinsonian rats. Catechol-O-methyltransferase (COMT) inhibitors increase the half-life and bioavailability of levodopa, providing more continuous dopamine receptor stimulation. This raises the possibility of using levodopa and a COMT inhibitor not only to treat motor complications, but also to prevent their development. Male Sprague-Dawley rats received a unilateral 6-hydroxydopamine (6-OHDA) administration in the nigrostriatal pathway. Two sets of experiments were performed. First, animals were treated with levodopa (50 mg/kg/day with benserazide 12.5 mg/kg/day, twice daily (b.i.d.), intraperitoneally (i.p.) for 22 days. On day 23, animals received either entacapone (30 mg/kg, i.p.) or vehicle with each levodopa dose. In the second set, animals were treated either with levodopa (50 mg/kg/day, i.p.) plus entacapone (30 mg/kg/day, i.p.) or levodopa (50 mg/kg/day, i.p.) plus vehicle, administered two or three times daily [b.i.d. or thrice daily (t.i.d.), respectively] for 22 consecutive days. Entacapone both reversed and prevented the shortening of the motor response duration that defines "wearing-off" motor fluctuations. Entacapone also decreased the frequency of failures to levodopa. The combination of levodopa and entacapone may reduce the likelihood of motor fluctuation development and may thus become a valuable approach to treat Parkinson disease whenever levodopa is needed.

Role of COMT inhibitors and dopamine agonists in the treatment of motor fluctuations

Although levodopa remains the most effective drug for the symptomatic treatment of Parkinson's disease (PD), there are significant limitations to its chronic use. Growing preclinical and clinical evidence suggests that the severity of motor fluctuations is influenced both by PD severity and pulsatile stimulation of striatal dopamine receptors. Current management of motor fluctuations is based primarily on strategies to prolong the effects of dopaminergic stimulation. This prolongation is accomplished either through the use of long-acting dopaminergic drugs or prolonging of the effects of levodopa. During the past decade, the armamentarium of dopamine agonists increased and agents that prolong the plasma half-life of levodopa became available. Furthermore, recent clinical trials provide evidence-based approaches to improve the management of motor fluctuations in patients with advanced and early PD.

Delayed administration may improve entacapone effects in parkinsonian patients non-responding to the drug

BACKGROUND

Entacapone is a COMT inhibitor used in Parkinson's disease (PD) patients, as an adjunctive therapy to L-dopa in order to prolong its bioavailability and thus its clinical effect. However, previous studies reported entacapone-induced L-dopa to have lower C(max) and delayed t(max) values, coupled with a delayed onset of the clinical effect, possibly suggesting an interference between the two drugs. The aim of our study was to evaluate whether a delayed entacapone administration in association with standard L-dopa/carbidopa, may in some subjects improve the entacapone effects on L-dopa AUC and thus on the clinical 'on time' duration.

METHODS

Twenty-eight idiopathic advanced PD patients were blindly evaluated in three different test days, following administration of carbidopa/L-dopa or carbidopa/L-dopa plus co-administered entacapone or plus entacapone administered with 30 min of delay.

RESULTS

The AUC, the 'on time' and UPDRS score of the whole group were improved by both modalities of entacapone administration. An ex post analysis showed that the delayed entacapone administration produced a significant improvement in a subgroup of 10 non-responding patients to the co-administration.

CONCLUSION

We suggest that the delayed administration should be attempted in the subjects not improved by entacapone co-administration.

Wireless real-time electronic data capture for self-assessment of motor function and quality of life in Parkinson's disease

Frequent assessment of the symptoms in Parkinson's disease (PD) is important in both clinical and experimental settings, especially when motor fluctuations are present. Patient diaries are increasingly used in studies, allowing patients to stay in their home environments. However, traditional paper diaries may not reflect reality because of a lack in compliance or retrospective data entries. This study presents a comparison between paper diaries and a new method, real-time data capture with a hand-held computer (electronic diary). Twenty patients with PD diagnosed at least 5 years previously were randomly assigned to use either a paper diary or an electronic diary on 8 days during 1 month. Questions were answered every 2 hours over a 12-hour period on each day. Median compliance was 88% with the electronic diary and 98% with the paper diary, although strict compliance to the scheduled times by patients using the paper diary was 78%. Neither age nor earlier experience with computers affected the patient's ability to use the electronic diary. Electronic diaries can be used for self-assessment of PD symptoms. The real-time feature provides fast access to clean data with knowledge of true compliance.

Entacapone improves the availability of L-dopa in plasma by decreasing its peripheral metabolism independent of L-dopa/carbidopa dose

AIMS

Entacapone is a peripherally acting catechol-O-methyltransferase (COMT) inhibitor. To improve the benefits of oral L-dopa in the treatment of Parkinson's disease (PD), entacapone is administered as a 200 mg dose with each daily dose of L-dopa. This study evaluated the effects of entacapone 200 mg on the pharmacokinetics and metabolism of L-dopa given as standard release L-dopa/carbidopa.

METHODS

Six different doses of l-dopa/carbidopa were investigated in this placebo-controlled, double-blind (regarding entacapone), randomized, single-dose study in 46 young healthy males. The subjects were divided into three groups (n = 14-16). Two different L-dopa/carbidopa doses were administered to each subject (50/12.5 mg and 150/37.5 mg, or 100/10 mg and 100/25 mg, or 200/50 mg and 250/25 mg). Each dose was given on two occasions; simultaneously with entacapone or with placebo, in random order, on two consecutive study visits, separated by a washout period of at least 3 weeks (four-way crossover design). Serial blood samples were drawn before dosing and up to 24 h after the dose and pharmacokinetic parameters of L-dopa, its metabolites, carbidopa, and entacapone were determined.

RESULTS

Entacapone increased the AUC(0,12 h) of L-dopa to a similar extent at all doses of L-dopa/carbidopa, that is by about 30-40% compared with placebo (P < 0.001, 95% CI 0.15, 0.40). When evaluated as the ratio of geometric means, entacapone slightly decreased the mean C(max) values for L-dopa at all L-dopa/carbidopa doses compared with placebo. When given with entacapone, higher plasma concentrations of L-dopa were maintained for a longer period at all doses of L-dopa/carbidopa. Entacapone also decreased the peripheral formation of 3-O-methyldopa (3-OMD) to about 55-60% of the placebo treatment level (P < 0.001, 95% CI -0.72, -0.35) and increased the mean AUC(0,12 h) of 3,4-dihydroxy-phenylacetic acid (DOPAC) 2-2.6-fold compared with placebo (P < 0.001, 95% CI 0.60, 1.10). The mean AUC(0,12 h) of 3-methoxy-4-hydroxy-phenylacetic acid (HVA) following entacapone was approximately 65-75% of that observed with placebo (P < 0.001-0.05, 95% CI -0.76, -0.01) at each L-dopa/carbidopa dose except the 50/12.5 mg dose (P > 0.05, 95% CI -0.59, 0.05). The metabolic ratios (MR, AUC metabolite/AUC L-dopa) also confirmed that entacapone significantly decreased the proportion of 3-OMD (P < 0.001, 95% CI -0.85, -0.68) and HVA (P < 0.001, 95% CI -1.01, -0.18) in plasma at each L-dopa/carbidopa dose, whereas the AUC DOPAC/AUC L-dopa ratio was increased again at all doses (P < 0.001, 95% CI 0.26, 0.90). Entacapone did not significantly affect the pharmacokinetics of carbidopa at any of the doses, nor did L-dopa/carbidopa affect the pharmacokinetics of entacapone.

CONCLUSIONS

The 200 mg dose of entacapone similarly and significantly increases the AUC of L-dopa by changing the metabolic balance of L-dopa independent of the L-dopa/carbidopa dose and therefore entacapone is likely to have a similar L-dopa potentiating effect independent of L-dopa dose.

Treatment options for Parkinson's disease

PURPOSE OF REVIEW

Parkinson's disease is a common neurodegenerative disorder. Clinical trials designed to assess the safety and efficacy of novel neuroprotective as well as symptomatic medical and surgical strategies are being performed to increase and enhance treatment options. The purpose of this review is to summarize these therapeutic options, emphasizing reports published in the last year.

RECENT FINDINGS

Experimental therapeutics in Parkinson's disease has focused on prevention of levodopa complications, treatment of dyskinesias associated with levodopa therapy, surgical intervention and neuroprotection.

SUMMARY

There are at least four important implications of the recent therapeutic trials: (1) the incidence of levodopa-related dyskinesias decreases as a result of initial use of dopamine agonists; (2) surgery, primarily in the form of the bilateral, high-frequency stimulation of the subthalamic nucleus, is highly effective in patients who are responsive to levodopa but experience marked motor fluctuation or other complications; (3) while neuroprotection has not yet been demonstrated with any currently used therapeutic agent, improved understanding of mechanisms of cell death will undoubtedly result in the discovery of new drugs with potential disease-modifying effects; and (4) implantation of fetal mesencephalon tissue and other grafts may be effective in younger patients with Parkinson's disease, but is associated with significant complications and remains experimental.

Entacapone in the management of Parkinson's disease

Entacapone is one of a new class of drugs, the catechol-O-methyltransferase (COMT) inhibitors, which expand the therapeutic options for Parkinson's disease by extending the action of levodopa. Entacapone is used in conjunction with levodopa and provides benefit to patients who suffer from motor fluctuations. Side effects include worsening of the dyskinesias associated with peak doses of levodopa, hypotension, constipation and urine discoloration. Unlike tolcapone, an earlier COMT inhibitor, entacapone does not require liver function monitoring.