Selegiline and levodopa in early or moderately advanced Parkinson's disease: a double-blind controlled short- and long-term study

Monoamine-oxidase Type B Inhibitors and Cognitive Functions in Parkinson's Disease: Beyond the Primary Mechanism of Action

Symptoms of cognitive impairment are rather common since the early stage of Parkinson's disease (PD); they aggravate with disease progression and may lead to dementia in a significant proportion of cases. Worsening of cognitive symptoms in PD patients depends on the progression of subcortical dopaminergic damage as well as the involvement of other brain neurotransmitter systems in cortical and subcortical regions. Beyond the negative impact on disability and quality of life, the presence and severity of cognitive symptoms may limit adjustments of dopamine replacement therapy along the disease course. This review focuses on the consequences of the administration of monoamine-oxidase type Binhibitors (MAOB-I) on cognition in PD patients. Two drugs (selegiline and rasagiline) are available for the treatment of motor symptoms of PD as monotherapy or in combination with L-DOPA or dopamine agonists in stable and fluctuating patients; a further drug (safinamide) is usable in fluctuating subjects solely. The results of available studies indicate differential effects according to disease stage and drug features. In early, non-fluctuating patients, selegiline and rasagiline ameliorated prefrontal executive functions, similarly to other dopaminergic drugs. Benefit on some executive functions was maintained in more advanced, fluctuating patients, despite the tendency of worsening prefrontal inhibitory control activity. Interestingly, high-dose safinamide improved inhibitory control in fluctuating patients. The benefit of high-dose safinamide on prefrontal inhibitory control mechanisms may stem from its dual mechanism of action, allowing reduction of excessive glutamatergic transmission, in turn secondary to increased cortical dopaminergic input.

A review on pathology, mechanism, and therapy for cerebellum and tremor in Parkinson's disease

Tremor is one of the core symptoms of Parkinson’s disease (PD), but its mechanism is poorly understood. The cerebellum is a growing focus in PD-related researches and is reported to play an important role in tremor in PD. The cerebellum may participate in the modulation of tremor amplitude via cerebello-thalamo-cortical circuits. The cerebellar excitatory projections to the ventral intermediate nucleus of the thalamus may be enhanced due to PD-related changes, including dopaminergic/non-dopaminergic system abnormality, white matter damage, and deep nuclei impairment, which may contribute to dysregulation and resistance to levodopa of tremor. This review summarized the pathological, structural, and functional changes of the cerebellum in PD and discussed the role of the cerebellum in PD-related tremor, aiming to provide an overview of the cerebellum-related mechanism of tremor in PD.

The MAO-B inhibitor deprenyl reduces the oral tremor and the dopamine depletion induced by the VMAT-2 inhibitor tetrabenazine

Tetrabenazine (TBZ) is prescribed for the treatment of chorea associated with Huntington's disease. Via inhibition of the vesicular monoamine transporter (VMAT-2), TBZ blocks dopamine (DA) storage and depletes striatal DA; this drug also has been shown to induce Parkinsonian motor side effects in patients. Recently, TBZ was shown to induce tremulous jaw movements (TJMs) in rats and mice. TJMs are an oral tremor that has many of the characteristics of Parkinsonian tremor in humans. The present study focused upon the ability of the well-established antiparkinsonian agent deprenyl to attenuate the behavioral and neurochemical effects of 2.0mg/kg TBZ. Deprenyl is a selective and irreversible inhibitor of monoamine oxidase-B, and administration of deprenyl produced a dose-related suppression of TBZ-induced TJMs. A second experiment employed in vivo microdialysis to examine extracellular DA levels in the ventrolateral striatum, the neostriatal region most closely associated with the production of TJMs, after administration of TBZ and deprenyl. Consistent with the behavioral data, TBZ alone produced a biphasic effect on extracellular DA, with an initial increases followed by a prolonged decrease during the period in which TJMs are displayed. Co-administration of deprenyl with TBZ increased DA levels compared to rats treated with TBZ alone. These results provide support for use of TBZ as a rodent model of Parkinsonism, and future studies should utilize this model to evaluate putative anti-Parkinsonian agents.

Summary of the recommendations of the EFNS/MDS-ES review on therapeutic management of Parkinson's disease

OBJECTIVE

To summarize the 2010 EFNS/MDS-ES evidence-based treatment recommendations for the management of Parkinson's disease (PD). This summary includes the treatment recommendations for early and late PD.

METHODS

For the 2010 publication, a literature search was undertaken for articles published up to September 2009. For this summary, an additional literature search was undertaken up to December 2010. Classification of scientific evidence and the rating of recommendations were made according to the EFNS guidance. In cases where there was insufficient scientific evidence, a consensus statement ('good practice point') is made.

RESULTS AND CONCLUSIONS

For each clinical indication, a list of therapeutic interventions is provided, including classification of evidence.

Selegiline: a reappraisal of its role in Parkinson disease

Selegiline at the doses used in Parkinson disease is a selective irreversible monoamine oxidase type B inhibitor, which potentiates dopaminergic function in the brain, and is used as monotherapy in early Parkinson disease or in combination with levodopa in more advanced disease. A renewed interest in monoamine oxidase type B inhibitors in the treatment of Parkinson disease has emerged after recent clinical trials of agents in this class. The use of selegiline monotherapy in early Parkinson disease is supported by the results of a large well-controlled trial in 800 patients (DATATOP) and several other studies, which demonstrated a symptomatic benefit, a reduction in disability, and a delay in the need to start levodopa therapy. Administered with levodopa in studies of up to 5 years' duration in patients with more advanced disease, selegiline improved disease-related disability, reduced the end-of-dose motor fluctuations, and also led to a reduction of the dose and dose frequency of levodopa required.Selegiline was the first drug to be investigated as a possible neuroprotective agent in patients with Parkinson disease, based on preclinical studies indicating protection of dopaminergic neurons from damage. The results of the extensive body of clinical trials, including delayed and lower levodopa requirements, may indeed suggest that selegiline, in addition to conferring symptomatic benefit, may have other effects on disease progression. Selegiline is well tolerated, and initial fears of increased mortality with the drug have not been borne out by subsequent robust meta-analyses.

Clinical trials of add-on medications in Parkinson's disease: Efficacy versus usefulness

Clinical trials designed to evaluate the efficacy of new anti-parkinsonian agents often employ an 'add-on' protocol in which patients with motor fluctuations on levodopa are randomized to receive active medication or placebo. Levodopa doses may not be increased, but can be decreased in response to dopaminergic side-effects such as increasing dyskinesia or hallucinations. Although these trials can delineate efficacy, additional studies are necessary to evaluate the usefulness of these medications in the clinical setting. The most important questions to be answered by such studies are: (1) Is the benefit derived from addon medication greater than that which could be brought about by further levodopa titration alone?, and (2) Can 'off' time be decreased and motor function improved without a proportionate increase in unwanted dyskinesia? The short-term symptomatic usefulness of an add-on medication can be evaluated by comparing the effects of the addition of active medication plus levodopa titration to further levodopa titration alone. We discuss the limitations of current add-on protocols as well as protocols which may help address the issue of clinical usefulness.

Orally disintegrating selegiline for the treatment of Parkinson's disease

The selective monoamine oxidase type B inhibitor selegiline is commonly administered as medical treatment to patients suffering from Parkinson's disease. The clinical value of conventional selegiline is, however, compromised by extensive first-pass metabolism, which reduces its bioavailability and leads to the production of possibly harmful methamfetamine metabolites. This review aims to evaluate a novel, orally disintegrating formulation of selegiline by examining scientific evidence from previous pharmacological and clinical studies. As a result of improved bioavailability, orally disintegrating selegiline can be administered at lower doses than conventional selegiline with similar clinical effect. It also leads to less variable selegiline blood concentrations and produces significantly less methamfetamine metabolites. We conclude that this novel formulation offers an interesting treatment option, especially for patients who report adverse events after initial treatment with conventional selegiline or who suffer from swallowing difficulties.

Review of the therapeutic management of Parkinson's disease. Report of a joint task force of the European Federation of Neurological Societies and the Movement Disorder Society-European Section. Part I: early (uncomplicated) Parkinson's disease

The aim of the study was to provide evidence-based recommendations for the management of early (uncomplicated) Parkinson's disease (PD), based on a review of the literature. Uncomplicated PD refers to patients suffering from the classical motor syndrome of PD only, without treatment-induced motor complications and without neuropsychiatric or autonomic problems. MEDLINE, Cochrane Library and International Network of Agencies for Health Technology Assessment (INAHTA) database literature searches were conducted. National guidelines were requested from all European Federation of Neurological Societies (EFNS) societies. Non-European guidelines were searched for using MEDLINE. Part I of the guidelines deals with prevention of disease progression, symptomatic treatment of motor features (parkinsonism), and prevention of motor and neuropsychiatric complications of therapy. For each topic, a list of therapeutic interventions is provided, including classification of evidence. Following this, recommendations for management are given, alongside ratings of efficacy. Classifications of evidence and ratings of efficacy are made according to EFNS guidance. In cases where there is insufficient scientific evidence, a consensus statement (good practice point) is made.

Pharmacological treatment of disabling tremor

Tremor is often a disabling primary condition or secondary to another disorder. No universally effective pharmacological agent exists for the treatment of essential tremor, and patients differ greatly in their response to therapies, thus requiring individualised regimens. Deep brain stimulation is the best option for patients with disabling, drug-resistant essential tremor. Resting tremor in Parkinson's disease is usually not the primary disabling feature, and in most cases, levodopa/carbidopa is satisfactory for many years. Young Parkinson's patients with dominant, disabling tremor benefit from anticholinergics in addition to dopaminergic therapies. However, older Parkinson's patients with more disabling tremor may suffer from dose-dependent side effects, and deep brain stimulation should be considered. This article outlines the available pharmacological agents and treatment considerations for various disabling tremors, including essential tremor and Parkinson's disease.

Treatment of Parkinson's disease in Japan

In this paper, the course of therapy for Parkinson's disease is outlined. The rationale for the use of DA-receptor-agonist (DA agonist) monotherapy or early combination therapy using levodopa and a DA agonist is that these therapies are asociated with a lower incidence of motor complications. However, the disease progresses, the use of levodopa in combination with a DA agonist results in motor complications and development of levodopa dependency in parkinsonian patients, because the effect of levodopa on parkinsonism is very strong. In this study, a positive correlation between the Hoehn-Yahr severity score at off-periods and duration of illness was observed in parkinsonian patients with long duration of illness. This indicates that responsiveness to dopaminergic therapy still exists even in patients in advanced stages of Parkinson's disease, indicating that continuous stimulation of DA receptors and reducing the excessive fluctuation in the plasma levodopa level possibly improve motor complications. If the dose of the DA agonist is simply increased without reduction of levodopa doses, dyskinesia worsens. Although levodopa therapy is essential in the case of patients in advanced stages of Parkinson's disease, the therapeutic principle, which depends on levodopa efficacy, must be changed. Reduction of the levodopa dose and administration of a sufficient dose of a DA agonist, which is equivalent to levodopa dose reduction, is one of the possible means of effective therapy of the disease.

Monoamine oxidase and catechol-O-methyltransferase inhibitors

Despite advances in the treatment of PD, there remain significant unmet therapeutic needs. This is particularly true at the later stages of the disease when dopaminergic therapy is complicated by motor fluctuations and dyskinesias. Inhibition of dopamine metabolism is a valuable adjunct to exogenous dopaminergic replacement. Inhibitors of MAO-B have been used to treat early and advanced PD for a number of years. Although controversy remains, existing evidence still raises the possibility that MAO-B inhibition may confer a protective effect in PD, delaying the progression of the underlying pathology. More recently, clinically useful inhibitors of COMT have become available. These medications largely act peripherally to increase the pool of available dopamine precursor and prolong the duration of effect of L-dopa. They are indicated primarily for control of motor fluctuations.

Monoamine oxidase inhibitors. A perspective on their use in the elderly

Monoamine oxidase inhibitors (MAOIs) are mainly used in psychiatry for the treatment of depressive disorders and in neurology for the treatment of Parkinson's disease. While the classical, nonselective and nonreversible MAOIs, such as phenelzine and tranylcypromine, are characterised by the risk of inducing a hypertensive crisis when dietary tyramine is ingested, the selective monoamine oxidase-B (MAO-B) inhibitor selegiline (deprenyl) and, even more so, the selective and reversible monoamine oxidase-A (MAO-A) inhibitor moclobemide, are free from this potential interaction. Drug tolerability data for the elderly show that moclobemide is one of the most well tolerated compounds. Selegiline, especially when used in combination with levodopa, can cause anorexia, dry mouth, dyskinesia and, most problematic, orthostatic hypotension. For the traditional MAOIs, phenelzine and tranylcypromine, published data are insufficient to be able to give a conclusive tolerability statement regarding the use of these compounds in elderly people. Although orthostatic hypotension occurs in most patients treated with traditional MAOIs, the incidence in elderly patients with depression does not appear to be greater than that reported with tricyclic antidepressants.

The effects of early selegiline therapy on long-term levodopa treatment and parkinsonian disability: an interim analysis of a Norwegian--Danish 5-year study. Norwegian-Danish Study Group

In this study, we investigated the effects of selegiline on levodopa treatment and parkinsonian disability over several years of treatment in patients with early Parkinson's disease (PD). The 163 patients were randomized to receive either selegiline or placebo in addition to levodopa in a double-blind, parallel-group study design, and the patients were to be followed up until a defined termination point or for 5 years. All patients had previously either never (two thirds) or for < 6 months (one third) received levodopa. After 1 year of treatment or at withdrawal from study or both, the patients were divided according to specified diagnostic criteria into groups of definite, probable, possible, or unlikely PD. The efficacy parameters were levodopa therapy, Unified Parkinson's Disease Rating Scale (UPDRS) with subscales, and the time to develop wearing-off fluctuations or reaching the termination point. Evaluation of efficacy was performed for all patients with PD and for patients with a definite and probable disease. The results of this study are based on an interim analysis when 80% of the 163 randomized patients had been followed up for > or = 3 years. Nine patients were excluded from the study because of protocol violations or because the patients were diagnosed as unlikely PD. At the time of interim analysis, 39 patients had been withdrawn from the study because of adverse effects or their own wish. Eighteen patients had reached the termination point, and 97 patients (observation time, 30-54 months) were still in the study. Among the patients receiving selegiline, we found a rather stable daily levodopa dose during 54 months of therapy, compared with an anticipated increase among patients with levodopa monotherapy. Concurrently, patients in the selegiline group showed a trend to develop less severe parkinsonian disability and a lower frequency of motor fluctuations and need for additional antiparkinsonian medication. The results of this study indicate that early combination therapy of selegiline and levodopa compared with levodopa monotherapy has an increasingly favorable impact on the long-term daily levodopa dose and may possibly delay the development of disability in PD.

The new generation of monoamine oxidase inhibitors

Irreversible and unspecific inhibitors of MAO were the first modern antidepressants, but after an initial success they fell into discredit due to adverse side effects. In the past two decades interest in MAO inhibitors has been renewed because of progress in basic research, a milestone being the finding that there are two subtypes of MAO, MAO-A and MAO-B. These are distinct proteins with high amino acid homology, coded by separate genes both located on the short arm of the human chromosome X. The enzyme subforms show different substrate specificities in vitro and different distributions within the central nervous system and in peripheral organs. In the central nervous system of man MAO-A seems to be mainly involved in the metabolism of 5 HT and noradrenaline, whereas 2-phenylethylamine and probably dopamine are predominantly deaminated by MAO-B. In the intestinal tract tyramine is mainly metabolized by MAO-A. These characteristics indicate distinct physiological functions of the two MAO-subforms. Several irreversible and reversible non-hydrazine inhibitors with relative selectivities for one of the MAO-subforms have been developed. They belong to various chemical classes with different modes of enzyme inhibition. These range from covalent mechanism based interaction (e.g. by propargyl- and allylamine derivatives) to pseudosubstrate inhibition (e.g. by 2-aminoethyl-carboxamides) and non-covalent interaction (e.g. by brofaromine, toloxatone and possibly moclobemide). The most important pharmacological effects of the new types of MAO inhibitors are those observed in neuropsychiatric disorders. The inhibitors of MAO-A show a favorable action in various forms of mental depression. The drugs seem to have about the same activity as other types of antidepressants, including tricyclic and related compounds as well as classical MAO inhibitors. The onset of action of the MAO-A inhibitors is claimed to be relatively fast. Other possible indications of these drugs include disorders with cognitive impairment, e.g. dementia of the Alzheimer type. In subjects with Parkinson's disease the MAO-B inhibitor L-deprenyl exerts a L-dopa-sparing effect, prolongs L-dopa action and seems to have a favorable influence regarding on-off disabilities. The action is in general transitory (months to several years). In addition L-deprenyl has been shown to delay the necessity for L-dopa treatment in patients with early parkinsonism. Whether the drug influence the progression of the disease is still a matter of debate. L-deprenyl also appears to have some antidepressant effect (especially in higher doses) and to exert a beneficial influence in other disorders, e.g. dementia of the Alzheimer type.(ABSTRACT TRUNCATED AT 400 WORDS)

Selegiline. A review of its pharmacology, symptomatic benefits and protective potential in Parkinson's disease

Selegiline (deprenyl) is a selective inhibitor of cerebral monoamine oxidase type B at the dosage (10 mg/day) used in patients with Parkinson's disease. Through this activity, the drug increases nigrostriatal dopamine levels, and may protect neurons against damage by free radicals and possibly exogenous neurotoxins. Selegiline also inhibits dopamine reuptake from the synaptic cleft. Because of its selectivity, selegiline 10mg daily does not prevent the breakdown and exacerbate the indirect pressor effects of dietary amines such as tyramine; it is devoid of the 'cheese' effect. Following oral administration, selegiline is rapidly metabolised to L-methamphetamine and L-amphetamine, which may account for the euphoria and insomnia seen in many patients, although potentiation of dopaminergic activity with concurrent levodopa appears more likely. The drug is a useful adjunct to levodopa in Parkinsonism, improving 'end-of-dose' fluctuations, producing modest improvements in motor function, and allowing a reduction in levodopa dosage. Indeed, if levodopa dosages are not decreased when selegiline is added to the therapeutic regimen, peak concentration dyskinesias due to levodopa are often exacerbated. However, symptomatic benefits are rarely maintained for more than a year and selegiline is relatively ineffective in allaying the abrupt swings in response to levodopa ('on/off' effects). When used alone in patients with mild disease, selegiline appears to slow the rate of symptom progression and may extend survival, through either neuroprotection or symptom relief. Whichever mechanism(s) is responsible, there is strong evidence to suggest that selegiline should be considered both in patients newly diagnosed with Parkinson's disease in an attempt to delay symptom progression, and in those experiencing dose-dependent fluctuations in response to levodopa.

Double-blind, crossover placebo controlled trial of selegiline in Parkinson's disease--an interim analysis

The response to selegiline was assessed in ten (2 females, 8 males) idiopathic parkinsonian patients with the wearing off response. Selegiline was compared to placebo in each patient in a double blind crossover study carried out over ten months. After 16 weeks of therapy selegiline significantly prolonged response to levodopa, extending response to 3 hours (p less than 0.05) in most patients and to 4 hours (p less than 0.001) in some patients. Baseline scores (zero time: 12 hours after their previous dose of medication) were also significantly better after selegiline therapy (p less than 0.05). Selegiline did not improve peak response (1 hour after medication) to levodopa indicating that these patients were on optimum therapy prior to receiving selegiline. Adverse effects (nausea (2), dyskinesia (2), fear reaction (1) and postural dizziness (1] occurred in 5 patients during the trial.

Selegiline in the treatment of daily fluctuations in disability of parkinsonian patients with long-term levodopa treatment

In order to evaluate in a double-blind manner the therapeutic efficacy of selegiline in the treatment of late-phase Parkinson's disease, 19 patients with end-of-dose type fluctuations were randomized for a double-blind cross-over trial receiving either selegiline 10 mg or placebo. Each period lasted 12 weeks. During a two week prestudy period the dose of levodopa was titrated to optimal levels. The disability was evaluated using the Columbia University Disability Scale (CUDS). The patients kept a daily diary to monitor closely the frequency and severity of their fluctuations and the side-effects of treatment. Their parkinsonian disability and all main symptoms improved significantly during selegiline treatment. The mean duration of action of a levodopa dose was significantly longer and there was significantly less daily end-of-dose and early morning akinesia during selegiline treatment. The side-effects were similar in both treatments. This double-blind study confirms the findings of earlier open studies that selegiline potentiates and prolongs the therapeutic effects of levodopa and thus its use is particularly beneficial in patients with end-of-dose type fluctuations in disability.