Anticholinergic withdrawal and benzhexol treatment in Parkinson's disease

Anticholinergic drugs for parkinsonism and other movement disorders

Anticholinergic (AC) drugs, a medication class that acts by blocking nicotinic and muscarinic acetylcholine receptors, were first utilized for therapeutic purposes in the mid-19th century. Initial applications were as symptomatic therapy for Parkinson disease (PD), a practice continuing to the present. Initially, the AC drugs used were naturally-occurring plant compounds. Synthetic AC drugs were developed in the late 1940s and predominated in neurological therapeutics. Until the advent of pharmaceuticals acting upon striatal dopaminergic motor pathways, AC drugs provided the only effective means for lessening tremors and other clinical problems of the PD patient. However, because dopaminergic compounds are so effective at meeting the needs of the typical PD patient, AC medications are far less utilized by clinicians today. In recent years, there has been only a few investigations of AC drugs as neurological treatments. This review will revisit the clinical landscape of AC pharmacology and application for movement disorders along with recent research in search of improving therapeutics with AC drugs.

Relative sparing of dopaminergic terminals in the caudate nucleus is a feature of rest tremor in Parkinson's disease

Resting tremor (RT) is a Parkinson's disease (PD) symptom with an unclear relationship to the dopaminergic system. We analysed data from 432 subjects from the Parkinson's Progression Markers Initiative, 57 additional PD patients and controls and 86 subjects referred for dopamine transporter single-photon emission computed tomography (DaT-SPECT). Caudate binding ratio (CBR), but not putamen binding ratio, was higher in RT patients. Furthermore, higher baseline CBR was linked to RT development. In the smaller cohorts, a 4-6 Hz oscillation-based metric from inertial sensors correlated with RT amplitude, distinguished controls from patients with reduced DaT binding and correlated with CBR in the latter group. In silico modelling uncovered that higher CBR in RT patients explained correlations between RT and DaT-SPECT found in several datasets, supporting a spurious origin for ipsilateral correlations between CBR and RT. These results suggest that caudate dopaminergic terminals integrity is a feature of RT with potential pathophysiological implications.

Safety overview of FDA-approved medications for the treatment of the motor symptoms of Parkinson's disease

INTRODUCTION

Parkinson's disease (PD) is among the most common of the neurodegenerative disorders. Treatment is primarily focused on correcting neurotransmitter imbalances. Several classes of medication are available for this purpose.

AREAS COVERED

A Medline search was performed to gather information about the safety of the medications approved for the treatment of the motor symptoms of PD. This was supplemented with additional articles obtained from online sources and information provided by the FDA and the manufacturers. The focus of this review is the side-effect and safety profiles of carbidopa/levodopa, dopamine agonists, selective monoamine oxidase inhibitors, catechol-o-methyltransferase inhibitors, anticholinergics and amantadine.

EXPERT OPINION

Though serious side-effects may occur, as a group, the medications used for the treatment of PD motor symptoms tend to produce side-effects that are mild to moderate in nature, and that primarily reflect the focus on dopaminergic therapies. Care plans for Parkinson's patients should be approached based on the needs of the individual as disease presentation, lifestyle, level of disability, concurrent disease states and the presence of non-motor symptoms make each case unique. Patients and caregivers must have realistic expectations about the use of PD medications.

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.

Rationale for current therapies in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that affects an estimated 1 million people in the US and tens of millions worldwide. Medication therapy has made significant advances and improvements especially over the last 10 years. A number of new treatments and new strategies have emerged and the quality of life for the average sufferer has improved. This review will describe the rationale and strategies for current medical therapies in PD, with special emphasis on the use of antipsychotic agents. Levodopa remains the most efficacious medication for the management of PD. Long-term use of levodopa, however, is associated with the development of motor fluctuations including dyskinesia. Trials with dopamine agonists have demonstrated a delay in the onset of dyskinesia with the use of this therapy. There is also active, ongoing investigation to determine whether a neuroprotective effect may be present with agonist therapy. Anticholinergics have been successfully used to treat tremor as well as sialorrhoea and urinary urgency. Catechol-O-methyltransferase inhibitors increase 'on time', decrease 'off time,' and improve motor scores. Continuous stimulation of dopamine receptors may decrease the fluctations observed with pulsatile delivery of anti-Parkinsonian medications, but this will require more study. Monoamine oxidase-B inhibitors, specifically selegiline, may provide symptomatic improvement; the question as to whether a neuroprotective benefit is present remains unanswered. Amantadine has demonstrated both symptomatic benefit and dyskinesia benefit in some patients. Selective dopamine blockers such as clozaril and quetiapine, have been shown to be effective in the treatment of psychosis. This class of medications is particularly useful as an adjunctive to levodopa and dopamine agonists. Doses of dopaminergic drugs can be escalated to treat Parkinsonian symptoms, whereas selective dopamine blockers can be added to block psychosis. Old management strategies required a reduction in dopaminergic therapy and therefore worsened Parkinsonian symptoms. Even though there have been great advances in the medical options for symptomatic management of PD, there are still many unmet needs for this patient population.

Anticholinergics for symptomatic management of Parkinson's disease

BACKGROUND

Anticholinergics were the first drugs available for the symptomatic treatment of Parkinson's disease and they are still widely used today, both as monotherapy and as part of combination regimes. They are commonly believed to be associated with a less favourable side effect profile than other antiparkinsonian drugs, in particular with respect to neuropsychiatric and cognitive adverse events. They have been claimed to exert a better effect on tremor than on other parkinsonian features.

OBJECTIVES

To determine the efficacy and tolerability of anticholinergics in the symptomatic treatment of Parkinson's disease compared to placebo or no treatment.

SEARCH STRATEGY

The literature search included electronic searches of the Cochrane Controlled Trials Register (The Cochrane Library, Issue 4, 2001), MEDLINE (1966 to 2001), Old Medline (1960-1965), Index Medicus (1927 - 1959), as well as handsearching the neurology literature including the reference lists of identified articles, other reviews and book chapters.

SELECTION CRITERIA

Randomised controlled trials of anticholinergic drugs versus placebo or no treatment in de-novo or advanced Parkinson's disease, either as monotherapy or as an add-on to other antiparkinsonian drugs were included. Trials of anticholinergic drugs that were never in general clinical use were excluded.

DATA COLLECTION AND ANALYSIS

Data was abstracted independently by two authors. Differences were settled by discussion among all authors. Data collected included patient characteristics, disease duration and severity, concomitant medication, interventions including duration and dose of anticholinergic treatment, outcome measures, rates of and reasons for withdrawals, and neuropsychiatric and cognitive adverse events.

MAIN RESULTS

The initial search yielded 14 potentially eligible studies, five of which were subsequently excluded. In three cases this was because they dealt with substances that had never been marketed or had not been licensed for as far as could be traced back. One trial had been published twice in different languages. One study was excluded based on the assessment of its methodological quality. The remaining nine studies were all of double-blind cross-over design and included 221 patients. Trial duration was between five and 20 weeks and drugs investigated were benzhexol (mean doses: 8 to 20 mg/d), orphenadrine (mean dose not reported), benztropine (mean dose not reported), bornaprine (8 to 8.25 mg/d), benapryzine (200 mg/d), and methixine (45 mg/d). Only one study involved two anticholinergic drugs. Outcome measures varied widely across studies and in many cases, the scales applied were the authors' own and were not defined in detail. Incomplete reporting of methodology and results was frequent. The heterogeneous study designs as well as incomplete reporting precluded combined statistical analysis. Five studies used both tremor and other parkinsonian features as outcome measures. Outcome measures in these five studies were too different for a combined analysis and results varied widely, from a significant improvement in tremor only to significant improvement in other features but not in tremor. All studies except one (dealing with methixine) found a significant improvement from baseline on the anticholinergic drug in at least one outcome measure. The difference between placebo and active drug was reported in four studies and was found to be significant in all cases. No study failed to show superiority of the anticholinergic over placebo. The occurrence of neuropsychiatric and cognitive adverse events was reported in all but three studies (in 35 patients on active drug versus 13 on placebo). The most frequently reported reason for drop-outs from studies was in patients on placebo due to withdrawal from pre-trial anticholinergic treatment.

REVIEWER'S CONCLUSIONS

As monotherapy or as an adjunct to other antiparkinsonian drugs, anticholinergics are more effective than placebo in improving motor function in Parkinson's disease. Neuropsychiatric and cognitive adverse events occur more frequently on anticholinergics than on placebo and are a more common reason for withdrawal than lack of efficacy. Results regarding a potentially better effect of the anticholinergic drug on tremor than on other outcome measures are conflicting and data do not strongly support a differential clinical effect on individual parkinsonian features. Data is insufficient to allow comparisons in efficacy or tolerability between individual anticholinergic drugs.

Reduction of Parkinsonian signs in patients with Parkinson's disease by dopaminergic versus anticholinergic single-dose challenges

We investigated the effect of an anticholinergic (biperiden) and a dopamine agonist (apomorphine) on tremor, rigidity, and akinesia in patients with idiopathic Parkinson's disease. In a standardized, crossover study design 17 patients received single-dose challenges of 5 mg biperiden intravenously and a previously determined dose of apomorphine subcutaneously on 2 consecutive days. Resting (RT), postural (PT), and action tremor (AT) were assessed using spectral analysis of accelerometer data, and Unified Parkinson's Disease Rating Scale (UPDRS) scores for rigidity and akinesia were determined before and after administration of the study drug. Both single-dose challenges significantly reduced the amplitude of RT, PT, and AT, but only apomorphine significantly reduced UPDRS scores for rigidity and akinesia. In only one patient was tremor reduced by the dopamine agonist but not by the anticholinergic. We found that anticholinergic and dopaminergic agents are both effective in reducing tremor in IPD, and there was no evidence for a selective anticholinergic responsiveness of parkinsonian tremor. Akinesia and rigidity, on the other hand, were not improved by biperiden. We therefore conclude that dopaminergic substances are as effective as anticholinergics in patients with parkinsonian tremor and additionally improve other parkinsonian signs.

Neuropsychiatric adverse effects of antiparkinsonian drugs. Characteristics, evaluation and treatment

Parkinson's disease (PD) is a progressive neurological condition that causes considerable disability in the elderly. Drugs used to treat PD, such as levodopa, offer symptomatic relief but often have neuropsychiatric adverse effects, most prominently psychosis and delirium. Aged patients and those with dementia are particularly vulnerable to these adverse effects. Evaluating PD patients with drug-induced neuropsychiatric adverse effects is made difficult by their complex clinical presentations. The treatment of drug-induced psychosis and delirium begins with manipulating the antiparkinsonian drug regimen, but this frequently worsens motor function. Atypical antipsychotics such as clozapine have been successfully employed to treat the psychosis without worsening the motor disability. Patient intolerance of clozapine therapy has prompted open-label studies with newer agents such as risperidone, remoxipride, zotepine, mianserin and ondansetron.

A risk-benefit assessment of drugs used in the management of Parkinson's disease

The introduction of levodopa therapy in the 1960s and subsequent advances in neuropharmacology have revolutionised the management of Parkinson's disease but at a cost. Adverse effects are common, and an erratic pattern of response may develop with long term therapy due to a poorly understood interaction between drug treatment and disease progression. Not all features of the disease respond to drugs, and certain aspects such as psychiatric symptoms and postural imbalance may indeed be exacerbated. Patients vary considerably in their tolerance of anti-Parkinsonian drugs. Individual assessment of each patient's medical, psychiatric and functional problems is required, with ongoing review and dose titration as the disease progresses. In recent years there has been increasing interest in whether it is possible to influence the progression of Parkinson's disease. As a result more complicated drug regimens are being advocated for use in newly diagnosed patients. Arguments for and against this approach, as opposed to traditional symptomatic treatment, are presented.

Current drug therapy for Parkinson's disease. A review

The impact of neuropharmacology has been greatest in 2 areas of clinical treatment: epilepsy and Parkinson's disease. This article covers the drug treatment of Parkinson's disease, a condition which characteristically affects the elderly population. The 5 drugs or groups of drugs used in the treatment of Parkinson's disease are: (a) anticholinergic drugs; (b) amantadine; (c) levodopa plus a peripheral decarboxylase inhibitor; (d) dopamine agonists; and (e) selegiline. Levodopa is still the most effective anti-Parkinsonian drug for most patients and is often combined with selegiline which may retard the rate of disease progression. The early use of dopamine agonists (such as bromocriptine) may prevent the subsequent development of response fluctuations. Once fluctuations have developed, they may be helped by the use of slow release levodopa preparations and, in the most severe cases, subcutaneous apomorphine.

On-off phenomenon: relation to levodopa pharmacokinetics and pharmacodynamics

Motor function in the moderately to severely affected parkinsonian patient is critically dependent upon delivery of levodopa to the striatum. This, in turn, is influenced by the fluctuating plasma concentrations of levodopa produced by the drug's short half-life and erratic absorption, and by modifiable transport at the blood-brain barrier. Duration of response to a single dose of levodopa is proportional to peak plasma drug levels, and paradoxical responses may occur when plasma concentrations are in the vicinity of minimum effective concentrations. Thus the strategy of administering frequent, small doses of levodopa may contribute additional unpredictability to a fluctuating clinical response imposed by pharmacokinetic factors.

Anti-parkinsonian drugs today

The drug treatment of Parkinson's disease has progressed through 3 main stages: firstly, the use of anticholinergic drugs and amantadine; then the introduction of levodopa and its association with peripheral decarboxylase inhibitors; and finally the use of direct acting dopamine agonist drugs. Levodopa, however, remains the most effective single drug in Parkinson's disease. Unfortunately, the side effects associated with long term levodopa treatment today constitute an important cause of functional disability. 'Positive' side effects such as involuntary movements and psychiatric disorder remain difficult to manage without causing an increase in Parkinsonian immobility; conversely, management of the 'negative' phenomenon of the 'off' period is limited by these same side effects. This has generated renewed interest in the highly complex pharmacokinetic and pharmacodynamic properties of levodopa, with the aim of reducing fluctuations in plasma levodopa (and hence brain dopamine) concentrations by sustained release oral or continuous parenteral administration of the drug.

Treatment of Parkinson's disease with agents other than levodopa and dopamine agonists: controversies and new approaches

Parkinson's disease is associated with a variety of neurotransmitter disturbances which may be further altered by its treatment with dopamine agonists. Based on this information a wide range of pharmacological approaches have been used in search of newer treatment alternatives and in hopes of reducing complications of long-term levodopa use. This paper reviews the various therapies which have had some success in the management of Parkinson's disease, other than levodopa and dopamine agonists. Special emphasis is placed on the many unresolved questions and controversies that exist in this area of neuropharmacology.

Advances in the management of parkinson's disease

The treatment of Parkinson's disease today is complex, time-consuming, but rewarding. The introduction of levodopa has not cured the disease, but has provided the most powerful therapy available yet. Its use is limited by side effects and careful titration to optimum dosage, often in combination with other drugs, is required. Despite best therapy, some patients never respond, and others begin to lose benefit after some years of therapy. New problems, such as the "on-off" effect have appeared with long-term treatment, and require careful adjustment of dosage. As with any replacement therapy, a balance between sub-optimal benefit and side effects has to be discovered and maintained by careful and frequent review. New approaches to treatment may offer further improvement in the near future.

L-dopa and carbidopa (sinemet) in the management of parkinsonism

Parkinsonism is a degenerative disease. A weakening in the responsiveness to dopamine replacement therapy affects many patients: thus 45% fail to maintain their initial improvement after 2 years' and 50% after 3 years' medication. However, by reducing the peripheral and systemic side actions of dopamine through the selective introduction of sinemet, a decarboxylase inhibitor+L-dopa combination, a partial amelioration of as much as 35% at 2 years, or 20% at 3 years, can be achieved. There is evidence, also, that the initial choice of anti-parkinsonian therapy may be critical to the long term prognosis.

Abnormal involuntary movements in relation to anticholinergics and levodopa therapy

During a study comparing levodopa with and without benserazide in Parkinsonism, 19 of 41 patients (42 per cent) receiving concomitant anticholinergic therapy developed abnormal involuntary movements (AIM), in contrast to 11 of 58 patients (19 per cent) receiving only levodopa. This difference is statistically significant. Discontinuation or dose-reduction of anticholinergics in 10 patients without altering the levodopa-dosage resulted in disappearance or amelioration of the AIM in nine cases. The Parkinsonism, however, aggravated subsequently, necessitating resumption of anticholinergics in five cases. These results establich further the facilitating effect of anticholinergics on the emergence of AIM.