Effects of methylphenidate on response to oral levodopa: a double-blind clinical trial

Experimental Dopamine Reuptake Inhibitors in Parkinson's Disease: A Review of the Evidence

Parkinson’s disease (PD) is the second most chronic neurodegenerative disorder worldwide. Deficit of monoamines, particularly dopamine, causes an individually varying compilation of motor and non-motor features. Constraint of presynaptic uptake extends monoamine stay in the synaptic cleft. This review discusses possible benefits of dopamine reuptake inhibition for the treatment of PD. Translation of this pharmacologic principle into positive clinical study results failed to date. Past clinical trial designs did not consider a mandatory, concomitant stable inhibition of glial monoamine turnover, i.e. with monoamine oxidase B inhibitors. These studies focused on improvement of motor behavior and levodopa associated motor complications, which are fluctuations of motor and non-motor behavior. Future clinical investigations in early, levodopa- and dopamine agonist naïve patients shall also aim on alleviation of non-motor symptoms, like fatigue, apathy or cognitive slowing. Oral levodopa/dopa decarboxylase inhibitor application is inevitably necessary with advance of PD. Monoamine reuptake (MRT) inhibition improves the efficacy of levodopa, the blood brain barrier crossing metabolic precursor of dopamine. The pulsatile brain delivery pattern of orally administered levodopa containing formulations results in synaptic dopamine variability. Ups and downs of dopamine counteract the physiologic principle of continuous neurotransmission, particularly in nigrostriatal, respectively mesocorticolimbic pathways, both of which regulate motor respectively non-motor behavior. Thus synaptic dopamine pulsatility overwhelms the existing buffering capacity. Onset of motor and non-motor complications occurs. Future MRT inhibitor studies shall focus on a stabilizing and preventive effect on levodopa related fluctuations of motor and non-motor behavior. Their long-term study designs in advanced levodopa treated patients shall allow a cautious adaptation of oral l-dopa therapy combined with a mandatory inhibition of glial monoamine turnover. Then the evidence for a preventive and beneficial, symptomatic effect of MRT inhibition on motor and non-motor complications will become more likely.

Current Perspectives on the Assessment and Management of Gait Disorders in Parkinson's Disease

Gait dysfunction is a key defining feature of Parkinson's disease (PD), and is associated with symptoms of freezing and an increased risk of falls. In this narrative review, we cover the putative mechanisms of gait dysfunction in PD, the assessment of gait abnormalities, and the management of symptoms caused by the inherent difficulty in walking. Our understanding of the causes of gait problems in PD has progressed in recent times, moving from neurocognitive theory to correlates of affected neuronal pathways. In particular, this can be shown to correspond with abnormalities in responses to dual-task paradigms and dysfunction in cholinergic signaling. Great progress has been made in the sophistication and precision of gait assessment; however, it has firmly remained in the research domain. There is significant momentum behind wearable technologies that can be used by patients in their own environment, acting as digital biomarkers that can not only reflect progression but also independently discriminate PD from non-PD individuals. The treatment of gait dysfunction has historically relied on physical therapies and training combined with a view to mitigating the impact of such consequences as falls. Pharmacological therapies that are the mainstay of treatment in PD have tended to address symptoms like bradykinesia; however, optimization of dopaminergic therapies likely has a positive effect on quality of gait. Other targets have been assessed with the goal of improving gait, of which medications that improve cholinergic signaling appear most promising. Neuromodulation techniques are increasingly used in the form of deep-brain stimulation; however, standard targets, such as the globus pallidus interna, have a modest effect on gait. Considerable benefit has been seen through targeting the pedunculopontine nucleus, and a dual-target approach may be warranted. Stimulation of the spinal cord and brain through direct or magnetic approaches has been assessed, but requires further evidence.

Efficacy and safety of 5-Hydroxytryptophan on levodopa-induced motor complications in Parkinson's disease: A preliminary finding

BACKGROUND AND PURPOSE

Several studies have indicated that altered serotonergic neurotransmission may contribute to the motor features commonly associated with Parkinson's disease (PD) drug treatment such as levodopa-induced dyskinesias (LIDs). 5-Hydroxytryptophan (5-HTP) is the immediate precursor of serotonin. We have recently demonstrated that 5-HTP produces significant antidyskinetic effects in a rat model of PD. To date, there has been inconsistent research on the use of 5-HTP in PD. The purpose of this study was to compare the effects of 5-HTP versus placebo on levodopa-induced motor complications in PD patients.

MATERIAL AND METHODS

A single-center, randomized, double-blind placebo-controlled cross-over study was performed. A total of 12 PD patients were diagnosed with LIDs and motor fluctuactions and subsequently were randomized to intervention; 11 subjects completed the entire 16-week protocol. Patients received placebo or 50 mg of 5-HTP daily in a cross-over design over a period of 4 weeks. For the assessment of efficacy on the motor functions and motor complications, the UPDRS (parts III and IV), Unified Dyskinesia Rating Scale (UDysRS), Wearing-Off Questionnaire (WOQ-19) and the self-reported 24-h home dyskinesia diaries were obtained at baseline and weeks 4, 8, 12 and 16 (T-end).

RESULTS

Repeated measures analysis revealed a significant improvement of LIDs during the 50 mg 5-HTP treatment as assessed by the UDysRS and UPDRS-IV scores.

CONCLUSIONS

This study provides preliminary evidence of clinical benefit of 5-HTP against LIDs in PD. Larger studies with a longer treatment duration and a wider range of doses are warranted to corroborate these findings.

Recent Advances in Drug Repurposing for Parkinson's Disease

As a long-term degenerative disorder of the central nervous system that mostly affects older people, Parkinson's disease is a growing health threat to our ever-aging population. Despite remarkable advances in our understanding of this disease, all therapeutics currently available only act to improve symptoms but cannot stop the disease progression. Therefore, it is essential that more effective drug discovery methods and approaches are developed, validated, and used for the discovery of disease-modifying treatments for Parkinson's disease. Drug repurposing, also known as drug repositioning, or the process of finding new uses for existing or abandoned pharmaceuticals, has been recognized as a cost-effective and timeefficient way to develop new drugs, being equally promising as de novo drug discovery in the field of neurodegeneration and, more specifically for Parkinson's disease. The availability of several established libraries of clinical drugs and fast evolvement in disease biology, genomics and bioinformatics has stimulated the momentums of both in silico and activity-based drug repurposing. With the successful clinical introduction of several repurposed drugs for Parkinson's disease, drug repurposing has now become a robust alternative approach to the discovery and development of novel drugs for this disease. In this review, recent advances in drug repurposing for Parkinson's disease will be discussed.

Treatment options for postural instability and gait difficulties in Parkinson's disease

Introduction: Gait and balance disorders in Parkinson's disease (PD) represent a major therapeutic challenge as frequent falls and freezing of gait impair quality of life and predict mortality. Limited dopaminergic therapy responses implicate non-dopaminergic mechanisms calling for alternative therapies.Areas covered: The authors provide a review that encompasses pathophysiological changes involved in axial motor impairments in PD, pharmacological approaches, exercise, and physical therapy, improving physical activity levels, invasive and non-invasive neurostimulation, cueing interventions and wearable technology, and cognitive interventions.Expert opinion: There are many promising therapies available that, to a variable degree, affect gait and balance disorders in PD. However, not one therapy is the 'silver bullet' that provides full relief and ultimately meaningfully improves the patient's quality of life. Sedentariness, apathy, and emergence of frailty in advancing PD, especially in the setting of medical comorbidities, are perhaps the biggest threats to experience sustained benefits with any of the available therapeutic options and therefore need to be aggressively treated as early as possible. Multimodal or combination therapies may provide complementary benefits to manage axial motor features in PD, but selection of treatment modalities should be tailored to the individual patient's needs.

Freezing of Gait in Parkinsonism and its Potential Drug Treatment

Freezing of gait (FOG) is a heterogeneous symptom. Studies of treatment for FOG are scarce. Levodopa and monoamine oxidase inhibitors (rasagiline and selegiline) have shown effective improvement for FOG. Other drugs, such as L-threo-3, 4-dihydroxyphenylserine, amantadine, and botulinum toxin have exhibited some beneficial effects. The present review summarizes the potential drug treatment for FOG in Parkinsonism.

Rasagiline for the symptomatic treatment of fatigue in Parkinson's disease

BACKGROUND

Fatigue affects 40% to 50% of all PD patients and is a leading cause of disability, with no clearly established or efficacious established treatments.

METHODS

In this double-blinded, placebo-controlled, pilot trial, we investigated whether rasagiline improved fatigue among PD patients. Subjects were randomized to 1 mg daily of rasagiline or placebo for 12 weeks. The primary endpoint was a change in the Modified Fatigue Impact Scale from baseline to week 12.

RESULTS

Thirty PD subjects (16 men), with Modified Fatigue Impact Scale baseline score of 67 ± 15, were randomized (16 to rasagiline vs. 14 to placebo). Significant improvement was noted in the mean Modified Fatigue Impact Scale score of the rasagiline group (12 points) as compared to placebo (8.5 points) from baseline to week 12 (P = 0.003).

CONCLUSION

In this pilot study, rasagiline at a dose of 1 mg per day improved fatigue. Larger randomized studies are needed to confirm this finding.

Pharmacological treatment in Parkinson's disease: Effects on gait

Gait impairments are a hallmark of Parkinson's disease (PD), both as early symptom and an important cause of disability later in the disease course. Although levodopa has been shown to improve gait speed and step length, the effect of dopamine replacement therapy on other aspects of gait is less well understood. In fact, falls are not reduced and some aspects of postural instability during gait are unresponsive to dopaminergic treatment. Moreover, many medications other than dopaminergic agents, can benefit or impair gait in people with PD. We review the effects of pharmacological interventions used in PD on gait, discriminating, whenever possible, among effects on four components of everyday mobility: straight walking, gait initiation, turning, gait adaptability. Additionally, we summarize the effects on freezing of gait. There is substantial evidence for improvement of spatial characteristics of simple, straight-ahead gait with levodopa and levodopa-enhancing drugs. Recent work suggests that drugs aiming to enhance the acetylcholine system might improve gait stability measures. There is a lack of well-designed studies to evaluate effects on more complex, but highly relevant walking abilities such as turning and making flexible adjustments to gait. Finally, paucity in the literature exists on detrimental effects of drugs used in PD that are known to worsen gait and postural stability in the elderly population.

Dopamine Reuptake Inhibitors in Parkinson's Disease: A Review of Nonhuman Primate Studies and Clinical Trials

Striatal dopamine deficiency is the core feature of the pathology of Parkinson's disease (PD), and dopamine replacement with l-3,4-dihydroxyphenylalanine (l-DOPA) is the mainstay of PD treatment. Unfortunately, chronic l-DOPA administration is marred by the emergence of dyskinesia and wearing-off. Alternatives to l-DOPA for alleviation of parkinsonism are of interest, although none can match the efficacy of l-DOPA to date. Catechol-O-methyltransferase and monoamine oxidase inhibitors are currently used to alleviate wearing-off, but they do not increase "on-time" without exacerbating dyskinesia. Alternate approaches to dopamine replacement in parkinsonism generally (and to wearing-off and dyskinesia, specifically) are therefore urgently needed. Inasmuch as they increase synaptic dopamine levels, dopamine transporter (DAT) inhibitors, whether they are selective or have actions on noradrenaline or serotonin transporters, theoretically represent an attractive way to alleviate parkinsonism per se and potentially enhance l-DOPA antiparkinsonian action (provided that sufficient dopamine terminals remain within the striatum). Several nonhuman primate studies and clinical trials have been performed to evaluate the potential of DAT inhibitors for PD. In this article, we review nonhuman primate studies and clinical trials, we summarize the current knowledge of DAT inhibitors in PD, and we propose a hypothesis as to how tailoring the selectivity of DAT inhibitors might maximize the benefits of DAT inhibition in PD.

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.

Monoamine reuptake inhibitors in Parkinson's disease

The motor manifestations of Parkinson's disease (PD) are secondary to a dopamine deficiency in the striatum. However, the degenerative process in PD is not limited to the dopaminergic system and also affects serotonergic and noradrenergic neurons. Because they can increase monoamine levels throughout the brain, monoamine reuptake inhibitors (MAUIs) represent potential therapeutic agents in PD. However, they are seldom used in clinical practice other than as antidepressants and wake-promoting agents. This review article summarises all of the available literature on use of 50 MAUIs in PD. The compounds are divided according to their relative potency for each of the monoamine transporters. Despite wide discrepancy in the methodology of the studies reviewed, the following conclusions can be drawn: (1) selective serotonin transporter (SERT), selective noradrenaline transporter (NET), and dual SERT/NET inhibitors are effective against PD depression; (2) selective dopamine transporter (DAT) and dual DAT/NET inhibitors exert an anti-Parkinsonian effect when administered as monotherapy but do not enhance the anti-Parkinsonian actions of L-3,4-dihydroxyphenylalanine (L-DOPA); (3) dual DAT/SERT inhibitors might enhance the anti-Parkinsonian actions of L-DOPA without worsening dyskinesia; (4) triple DAT/NET/SERT inhibitors might exert an anti-Parkinsonian action as monotherapy and might enhance the anti-Parkinsonian effects of L-DOPA, though at the expense of worsening dyskinesia.

Clinical syndromes: Parkinsonian gait

Disturbances of gait manifest in almost all cases of Parkinson's disease (PD), often leading to loss of mobility and increased mortality. In this review a clinically oriented approach to gait disorders in different stages of PD is presented. In addition, interactions between motor behavior and mental processing will be discussed. Analyzing the clinical features of gait can be helpful to differentiate PD from atypical forms of parkinsonism. Bedside tests to distinguish parkinsonian gait disorders are reviewed. There is still an unmet need to effectively treat complex gait disturbances, which are frequently not responsive to dopamine replacement medication. We thus present current approaches for the management of dopa-refractory gait disorders.

Methylphenidate : a treatment for Parkinson's disease?

Parkinson's disease (PD) affects about 1 % of the population over the age of 60 years and is characterized by a combination of rest tremor, bradykinesia, rigidity, postural instability, stooped posture and freezing of gait (FoG). However, the clinical spectrum also spans a wide range of non-motor symptoms, such as depression, apathy, cognitive disorders, sleepiness, fatigue and pain. Given that the loss of dopamine in the striatum is the primary pathochemical hallmark in PD, pharmacological treatment of the disease has focused on restoring dopaminergic neurotransmission. The currently licensed dopaminergic treatments for PD modulate all the key steps in the dopamine transmission except the most powerful determinant of extracellular dopamine concentrations: the presynaptic dopamine transporter (DaT). Methylphenidate is a CNS stimulant that blocks the DaT and the noradrenaline (norepinephrine) transporter in the striatum and the prefrontal cortex in particular. Here, we report on and discuss the main open-label studies and randomized controlled trials on the effect of methylphenidate on severe gait disorders (e.g. the FoG) and non-motor symptoms in advanced PD. The various pharmacodynamic effects of methylphenidate mean that the drug may have significant value in the treatment of PD. However, there is a lack of randomized controlled trials in this field. Furthermore, more rigorous selection of the types and doses of the associated dopaminergic treatments is required because these parameters may profoundly influence the mechanisms of action of methylphenidate and the clinical outcomes. Pharmacogenetic tools could be of use in better defining study patients as a function of their dopaminergic metabolism and drug responsiveness.

Fatigue rating scales critique and recommendations by the Movement Disorders Society task force on rating scales for Parkinson's disease

Fatigue has been shown to be a consistent and common problem in Parkinson's disease (PD) in multiple countries and cultures. It is one of the most disabling of all symptoms, including motor dysfunction, and appears early, often predating the onset of motor symptoms. Several studies of the epidemiology of fatigue have been published, often using different scales, but few on treatment. The Movement Disorder Society (MDS) commissioned a task force to assess available clinical rating scales, critique their psychometric properties, summarize their clinical properties, and evaluate the evidence in support of their use in clinical studies in PD. Six clinical researchers reviewed all studies published in peer reviewed journals of fatigue in PD, evaluated the scales' previous use, performance parameters, and quality of validation data, if available. Scales were rated according to criteria provided by the MDS. A scale was "recommended" if it has been used in clinical studies beyond the group that developed it, has been used in PD and psychometric studies have established that it is a valid, reliable and sensitive to change in people with PD. Requiring a scale to have demonstrated sensitivity to change in PD specifically rather than in other areas in order to attain a rating of "recommended" differs from the use of this term in previous MDS task force scale reviews. "Suggested" scales failed to meet all the criteria of a "recommended" scale, usually the criterion of sensitivity to change in a study of PD. Scales were "listed" if they had been used in PD studies but had little or no psychometric data to assess. Some scales could be used both to screen for fatigue as well as to assess fatigue severity, but some were only used to assess severity. The Fatigue Severity Scale was "recommended" for both screening and severity rating. The Fatigue Assessment Inventory, an expanded version of the Fatigue severity Scale, is "suggested" for both screening and severity. The Functional Assessment of Chronic Illness Therapy-Fatigue was "recommended" for screening and "suggested" for severity. The Multidimensional Fatigue Inventory was "suggested" for screening and "recommended" for severity. The Parkinson Fatigue Scale was "recommended" for screening and "suggested" for severity rating. The Fatigue Severity Inventory was "listed" for both screening and severity. The Fatigue Impact Scale for Daily Use, an adaptation of the Fatigue Impact Scale was "listed" for screening and "suggested" for severity. Visual Analogue and Global Impression Scales are both "listed" for screening and severity. The committee concluded that current scales are adequate for fatigue studies in PD but that studies on sensitivity and specificity of the scales are still needed.

Non-motor dopamine withdrawal syndrome after surgery for Parkinson's disease: predictors and underlying mesolimbic denervation

Apathy has been reported to occur after subthalamic nucleus stimulation, a treatment of motor complications in advanced Parkinson's disease. We carried out a prospective study of the occurrence of apathy and associated symptoms, predictors and mechanisms in the year following subthalamic stimulation. Dopamine agonist drugs were discontinued immediately after surgery and levodopa was markedly reduced within 2 weeks. Apathy and depression were assessed monthly, using the Starkstein apathy scale and the Beck Depression Inventory. Dopamine agonists were re-introduced if patients developed apathy or depression. Preoperative non-motor fluctuations were evaluated using the Ardouin Scale. Depression, apathy and anxiety were evaluated both on and off levodopa. Analysis of predictors of apathy was performed using a Cox proportional hazard model. Twelve patients who developed apathy and a control group of 13 patients who did not underwent [11C]-raclopride positron emission tomography scanning before and after oral intake of methylphenidate. In 63 patients with Parkinson's disease treated with subthalamic stimulation, dopaminergic treatment was decreased by 82% after surgery. Apathy occurred after a mean of 4.7 (3.3-8.2) months in 34 patients and was reversible in half of these by the 12-month follow-up. Seventeen patients developed transient depression after 5.7 (4.7-9.3) months and these fell into the apathy group with one single exception. At baseline, fluctuations in depression, apathy and anxiety scores were greater in the group with apathy. Fluctuations in apathy, depression and anxiety ratings during a baseline levodopa challenge were also significant predictors of postoperative apathy in univariate analysis, but not motor and cognitive states or the level of reduction of dopaminergic medication. The multivariate model identified non-motor fluctuations in everyday life and anxiety score during the baseline levodopa challenge as two independent significant predictors of postoperative apathy. Without methylphenidate, [11C]-raclopride binding potential values were greater in apathetic patients bilaterally in the orbitofrontal, dorsolateral prefrontal, posterior cingulate and temporal cortices, left striatum and right amygdala, reflecting greater dopamine D2/D3 receptor density and/or reduced synaptic dopamine level in these areas. The variations of [11C]-raclopride binding potential values induced by methylphenidate were greater in non-apathetic patients in the left orbitofrontal cortex, dorsolateral prefrontal cortex, thalamus and internal globus pallidus and bilaterally in the anterior and posterior cingulate cortices, consistent with a more important capacity to release dopamine. Non-motor fluctuations are related to mesolimbic dopaminergic denervation. Apathy, depression and anxiety can occur after surgery as a delayed dopamine withdrawal syndrome. A varying extent of mesolimbic dopaminergic denervation and differences in dopaminergic treatment largely determine mood, anxiety and motivation in patients with Parkinson's disease, contributing to different non-motor phenotypes.

Novel therapeutic strategies in Parkinson's disease

PD is a neurodegenerative disorder triggered by genetic and/or environmental factors and the pathological processes begin many years before motor symptom manifestation. Several drugs are available to treat PD, but there are still many aspects of the disease that have not been well addressed. These include nonmotor symptoms, disease progression, and preventing levodopa-induced motor complications. Besides the concept of continuous dopaminergic stimulation, the benefit of which has not been proved in clinical settings (see the STRIDE-PD trial), the nondopaminergic drugs offer promising alternatives to dopaminergic medication. However, modification and further development of dopaminergic molecules may provide significant symptomatic improvement and improved quality of life. In this review, we summarized new treatments that are in the pipeline, with patients being recruited for clinical trials. Among the compounds being studied are well-known ones (e.g., folic acid or methylphenidate), which have been used in other diseases, and newly developed drugs with known mode of action (e.g., the dopamine agonist aplindore) or compounds with completely new mechanisms, which have not yet been used in clinical settings (e.g., levetiracetam or Neu 120). A major breakthrough in treating Parkinson's disease cannot be expected with molecules from the first two cases, whereas significant clinical benefits can be predicted with the drugs in the last group. However, without these large-scale, well-designed, multicenter trials, the promising preclinical results cannot be directly adopted in patient care. Hopefully, some of these trials will end soon with positive results, and certain drugs will become available with which to treat PD patients, although still many aspects (e.g., the most problematic one, the question of neuroprotection) still need to be addressed.

Fatigue in Parkinson disease, stroke, and traumatic brain injury

Fatigue is a serious, QoL-limiting symptom of many neurologic conditions. Physicians should be thorough and consistent in their assessment for this problem and not let motor symptoms monopolize an office visit. Although the use of pharmacology to treat this problem has predominantly only anecdotal evidence of efficacy, several nonpharmacologic interventions may prove helpful. The directions of future research should aim to create clear treatment guidelines using the pharmacologic agents available.

Methylphenidate for the treatment of Parkinson disease and other neurological disorders

Methylphenidate (MPH) is a central nervous system stimulant derived from an amphetamine and acts as a potent inhibitor of catecholamine reuptake and increases dopamine levels in the brain. Methylphenidate is widely used for the treatment of children and adults with attention deficit hyperactivity disorder. Because the dopaminergic system is critical to the pathological process in Parkinson disease (PD), it has been suggested that MPH, which increases dopaminergic stimulation at the postsynaptic receptor level, may provide symptomatic relief in PD patients. This article reviews those studies that have evaluated the potential of MPH to treat the motor and cognitive aspects of PD, summarizes the evidence for clinical use in other neurological diseases, and briefly reviews the physiological mechanisms whereby MPH may bring about its therapeutic effects. Methylphenidate does seem to be useful for ameliorating cognitive, affective, and motor deficits in PD and in other neurological patients; however, additional studies are needed before MPH can be routinely prescribed as an adjunct therapy in these populations.

Methylphenidate improves fatigue scores in Parkinson disease: a randomized controlled trial

Fatigue is a common nonmotor symptom in idiopathic Parkinson disease (IPD) that can prominently affect everyday function. This study was a randomized, double-blind, placebo-controlled trial evaluating methylphenidate for the treatment of fatigue in patients with IPD maintained on their regular medications. Thirty-six patients were randomized to receive either methylphenidate (10 mg three times per day; n = 17) or placebo (n = 19) for 6 weeks. Primary outcomes were the change from baseline on two separate self-report fatigue questionnaires: the Fatigue Severity Scale (FSS) and the Multidimensional Fatigue Inventory (MFI). Secondary outcomes included the Unified Parkinson Disease Rating Scale (UPDRS) motor score and the five individual domains of the MFI. Fourteen patients in the methylphenidate group and 16 patients in the control group remained on the intervention for the entire study period. In the treatment arm, mean FSS score was reduced by 6.5 points (from a baseline of 43.8) and mean MFI score was reduced by 8.4 points (from a baseline of 51.0). Both these reductions were significant (P < 0.04). Smaller reductions in the placebo group were nonsignificant. Mean UPDRS motor score did not change significantly in either group. Analysis of MFI subscores showed a significant reduction in General Fatigue in the methylphenidate group (P < 0.001). Overall, adverse effects of medication were more frequent in the placebo group. In conclusion, methylphenidate was effective in lowering fatigue scores in patients with IPD following a 6-week treatment period.