A controlled study comparing trihexyphenidyl hydrochloride plus levodopa with placebo plus levodopa in patients with Parkinson's disease

Regional cerebral cholinergic nerve terminal integrity and cardinal motor features in Parkinson's disease

Clinical effects of anti-cholinergic drugs implicate cholinergic systems alterations in the pathophysiology of some cardinal motor impairments in Parkinson’s disease. The topography of affected cholinergic systems deficits and motor domain specificity are poorly understood. Parkinson's disease patients (n = 108) underwent clinical and motor assessment and vesicular acetylcholine transporter [¹⁸F]-fluoroethoxybenzovesamicol PET imaging. Volumes-of-interest-based analyses included detailed thalamic and cerebellar parcellations. Successful PET sampling for most of the small-sized parcellations was available in 88 patients. A data-driven approach, stepwise regression using the forward selection method, was used to identify cholinergic brain regions associating with cardinal domain-specific motor ratings. Regressions with motor domain scores for model-selected regions followed by confounder analysis for effects of age of onset, duration of motor disease and levodopa equivalent dose were performed. Among 7 model-derived regions associating with postural instability and gait difficulties domain scores three retained significance in confounder variable analysis: medial geniculate nucleus (standardized β = −0.34, t = −3.78, P = 0.0003), lateral geniculate nucleus (β = −0.32, t = −3.4, P = 0.001) and entorhinal cortex (β = −0.23, t = −2.6, P = 0.011). A sub-analysis of non-episodic postural instability and gait difficulties scores demonstrated significant effects of the medial geniculate nucleus, entorhinal cortex and globus pallidus pars interna. Among 6 tremor domain model-selected regions two regions retained significance in confounder variable analysis: cerebellar vermis section of lobule VIIIb (β = −0.22, t = −2.4, P = 0.021) and the putamen (β = −0.23, t = −2.3, P = 0.024). None of the three model-selected variables for the rigidity domain survived confounder analysis. Two out of the four model-selected regions for the distal limb bradykinesia domain survived confounder analysis: globus pallidus pars externa (β = 0.36, t = 3.9, P = 0.0097) and the paracentral lobule (β = 0.26, t = 2.5, P = 0.013). Emphasizing the utility of a systems-network conception of the pathophysiology of Parkinson's disease cardinal motor features, our results are consistent with specific deficits in basal forebrain corticopetal, peduncupontine-laterodorsal tegmental complex, and medial vestibular nucleus cholinergic pathways, against the background of nigrostriatal dopaminergic deficits, contributing significantly to postural instability, gait difficulties, tremor and distal limb bradykinesia cardinal motor features of Parkinson’s disease. Our results suggest significant and distinct consequences of degeneration of cholinergic peduncupontine-laterodorsal tegmental complex afferents to both segments of the globus pallidus. Non-specific regional cholinergic nerve terminal associations with rigidity scores likely reflect more complex multifactorial signalling mechanisms with smaller contributions from cholinergic pathways.

Comparison of effectiveness of trihexyphenidyl and levodopa on motor symptoms in Parkinson's disease

Despite anti-cholinergics being the oldest type of medication used for the treatment of Parkinson's disease (PD), the mechanism of action and exact benefit is unclear. This study compared the effectiveness of trihexyphenidyl (THP) and levodopa (LD) on motor symptoms in patients with PD. Patients with PD who are currently taking or had taken THP were recruited. UPDRS-III was done following overnight medication OFF state and 30 min, 60 min, 90 min, and 120 min after THP (4 mg). After a forty-eight-hour interval, UPDRS-III was assessed one hour after Levodopa/carbidopa (200/50 mg) in an overnight OFF state. Twenty patients with a mean age of 57.9 ± 7.8 years and mean duration of illness of 5.1 ± 3.6 years were recruited. UPDRS-III score reduction (%) with THP was maximum in the tremor sub-score (53.8 ± 22.8) and was significantly better compared to improvement in total-UPDRS-III (27.0 ± 14.7), bradykinesia-UPDRS-III (22.2 ± 27.2), rigidity-UPDRS-III (29.5 ± 28.0) and axial-UPDRS-III (8.1 ± 13.3) sub-score. In comparison, respective LD improvement was 67.1 ± 22.9 (tremor-UPDRS-III), 61.3 ± 14.4 (total-UPDRS-III), 67.9 ± 32.1 (bradykinesia-UPDRS-III), 65.3 ± 25.5 (rigidity-UPDRS-III) and 50.7 ± 16.0 (axial-UPDRS-III). Improvement (%) in tre-UPDRS-III post-THP was comparable to that of post-LD (53.8 ± 22.8 vs. 67.1 ± 22.9, p = 0.057). Those with same or better tremor response with THP had significantly milder baseline tremor severity than those who had better response with LD (tre-UPDRS-III-OFF, 10.0 ± 2.8 vs. 5.8 ± 4.0, p = 0.013). Both THP and LD showed significant improvement in UPDRS-III. With THP, the maximum degree of improvement was in the tremor sub-score and not significantly different to that obtained by LD. Those with better tremor response on THP had milder tremor severity.

Therapeutic strategies for Parkinson's disease: promising agents in early clinical development

INTRODUCTION

To date, no drug has demonstrated clinically indisputable neuroprotective efficacy in Parkinson's disease (PD). We also have no effective symptomatic treatment for disabling symptoms such as balance problems, and dementia, and we need to improve the efficacy and safety profile of drugs currently used in the management of motor complications.

AREAS COVERED

We examine the agents which appear to have most therapeutic promise based on concepts, feasibility in a reasonable time frame, and available clinical data and place an emphasis on disease-modifying treatments. PUBMED and Clinicaltrials.gov databases were searched for Phase I and II randomized trials for symptomatic or disease-modifying treatments considering only studies that began since 2010 or that were completed after 2015, up to 30 April 2020.

EXPERT OPINION

Encouraging progress has been made in our understanding of molecular pathways. We find passive immunization approaches against α-synuclein, LRRK2 kinase inhibitors, and treatment that can increase GCase activity, which have shown some efficacy on both GBA-mutated and non-mutated PD patients. The recognition of non-dopaminergic impairment and the prominent role of non-motor symptoms have prompted the development of trials on compounds that could tackle different neurotransmitter systems. Future approaches will encompass more personalized medicine strategies based on molecular signatures and non-motor phenotypes.

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.

The management of orthostatic hypotension in Parkinson's disease

Orthostatic hypotension (OH) is a common and disabling symptom affecting Parkinson's disease (PD) patients. We present the effect of the different therapies commonly used to manage PD on this clinical manifestation. For this purpose, we describe the relationship between OH and the current treatments employed in PD, such as L-DOPA, dopaminergic agonists, and continuous dopaminergic stimulation therapies. Additionally, we review the therapeutic measures that could be used to ameliorate OH. There are different approaches to deal with this manifestation, including pharmacological and non-pharmacological treatments, although none of them is specifically aimed for treating OH in PD.

Optimizing therapeutic effects in patients with comorbidities: drug-resistant tremor, autonomic dysfunction, psychiatric disorders, and cognitive impairment

Parkinsonism is a syndrome characterized by a combination of cardinal features including resting tremor, bradykinesia, rigidity, and loss of postural reflexes. The most common presentation of parkinsonism is the idiopathic variety first described by James Parkinson in 1817 now known as Parkinson's disease (PD). This article focuses on identifying the different subtypes of PD, with the recognition that treatment approaches may differ depending on the initial presenting feature. It also addresses issues related to the recognition and treatment of nonmotor comorbidities of PD, such as autonomic dysfunction and neuropsychiatric problems including depression and dementia.

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.

Limitations of current Parkinson's disease therapy

Levodopa and other dopaminergic medications drastically improve the motor symptoms and quality of life of patients with Parkinson's disease in the early stages of the disease. However, once the "honeymoon" period has waned, usually after a few years of dopaminergic therapy, patients become progressively more disabled despite an ever more complex combination of available antiparkinsonian treatments. Sooner or later, they suffer from "dopa-resistant" motor symptoms (speech impairment, abnormal posture, gait and balance problems), "dopa-resistant" nonmotor signs (autonomic dysfunction, mood and cognitive impairment, sleep problems, pain) and/or drug-related side effects (especially psychosis, motor fluctuations, and dyskinesias). Therefore, the current antiparkinsonian therapy cannot be considered as ideal with regard to both efficacy and safety.

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.

Frequency of levodopa-related dyskinesias and motor fluctuations as estimated from the cumulative literature

There is no clear consensus regarding the frequency (and hence, the risk), of dyskinesias or motor fluctuations during chronic levodopa therapy for Parkinson's disease (PD). Multiple clinical series have tabulated these frequencies since the advent of levodopa over 30 years ago. We were interested in determining: (1) the aggregate frequency figures in the existing literature; and (2) how clinical series from the early levodopa era, which included patients with longer durations of parkinsonism, compare to more recent (modern era) series. We searched MEDLINE for all English language publications reporting the cumulative frequency of levodopa-induced dyskinesias or motor fluctuations during discrete intervals of treatment. This generated 2,478 publications spanning 1966 through September 2000. Papers with appropriate titles or abstracts were reviewed; reference lists from published clinical series were a source of additional papers for review. This ultimately yielded 74 publications with adequate data, relating to 112 intervals of levodopa treatment. Series that included patients with PD-onset well before levodopa availability (pre-levodopa era) were separately analyzed from all subsequent series. Series were grouped by duration of levodopa therapy and the median frequencies of dyskinesias and motor fluctuations were tabulated for each group. The data were analyzed both with and without adjustment for the number (N) in each series. Among series containing pre-levodopa era patients, the median dyskinesia frequency was already 50% by 5-6 months of treatment. This contrasts with the modern era series where dyskinesias were reported later in treatment. The median dyskinesia frequency was slightly less than 40% by 4-6 years of levodopa therapy among modern era patients. Motor fluctuations (wearing-off) were not tabulated in most of the early levodopa series. Among modern era reports, motor fluctuations were nil during the first year of levodopa therapy but were experienced by approximately 40% of patients by 4-6 years of treatment. Similar results were found when the analyses were restricted to only prospective studies where levodopa motor complications were targeted outcome measures. The conclusions reached were: (1) patients from the pre-levodopa era experienced dyskinesias much earlier during levodopa treatment than modern era patients, perhaps because of longer durations of pre-existing PD; (2) in the present era, patients treated with levodopa therapy for 4-6 years have approximately a 40% likelihood of experiencing motor fluctuations and a risk of dyskinesias just short of 40%; and (3) these findings represent incident data and the prevalence of clinically important morbidity may be substantially less.

Tremor-predominant Parkinson's disease. Approaches to treatment

Parkinson's disease is a neurodegenerative disorder that manifests clinically with variable degrees of tremor, muscle rigidity, bradykinesia and postural instability. Tremor-predominant Parkinson's disease is characterised by prominent tremor of one or more limbs with a relative lack of significant rigidity and bradykinesia. Despite the lack of other disabling motor symptoms, the tremor of tremor-predominant Parkinson's disease can be very disabling, especially if a postural and kinetic component exists. A wide variety of treatments for Parkinson's disease tremor are currently available and include use of oral medications, injections with botulinum toxin and neurosurgical procedures. Some of the first line medications (levodopa, dopamine agonists, anticholinergics) are very effective in controlling tremor. However, some patients with Parkinson's disease tremors are unresponsive to first line drugs and treatment with second line medications (clozapine, amantadine, clonazepam, propranolol, neurontin) should be attempted. In the small number of patients with disabling tremor that is refractory to all medications, neurosurgical intervention should be considered. Both thermocoagulation and deep brain stimulation at several different neuroanatomical sites (thalamus, globus pallidus, subthalamic nucleus) offer good to excellent tremor control with relatively low risk to the patient.

The management of Parkinson's disease

It is useful to divide Parkinsonian patients into those whose signs are confined to tremor, rigidity and akinesia, and those with evidence of a more diffuse disturbance. The treatment of choice in the former is levodopa combined with a peripheral decarboxylase inhibitor. At the onset of the disease, when disability is minimal, amantadine or anticholinergic drugs may suffice. Bromocriptine is useful in some patients who derive only short-lived benefit from each dose of levodopa. The role of stereotactic surgery is now confined to patients with an incapacitating unilateral tremor which has not improved with drug therapy. In elderly patients with evidence of diffuse cerebral dysfunction such as dementia, grasp reflex, hyper-reflexia or severe postural hypotension, the beneficial effect of these drugs is often outweighed by the side effects. Small doses of levodopa alone may be tried. Anticholinergic drugs and amantadine should be avoided in such patients.

Parkinson's disease: Cogentin with Sinemet, a better response

1. A randomized, placebo controlled, double-blind cross-over study was conducted to evaluate the clinical efficacy of the anticholinergic agent, benztropine mesylate (CogentinR) in 29 patients with mild to moderate, idiopathic Parkinson disease. 2. Patients were maintained on a stable, therapeutically optimal dosage and schedule of levadopa-carbidopa (Sinemet) throughout the study. 3. Both the neurologist's and the patient's global assessments of treatment efficacy indicated that Sinemet plus benztropine mesylate resulted in significantly greater improvement than Sinemet plus placebo. 4. Qualitative and quantitative evaluations of relevant neurologic functions showed small, but statistically significant improvements for rigidity, finger tapping speed and activities of daily living in patients during the Sinemet plus benztropine mesylate treatment period. 5. At the completion of the study 16 patients chose to continue taking benztropine mesylate as an adjuvant to Sinemet. 6. No important adverse side effects occurred during the study.

Combination therapy of extrapyramidal disease with trihexyphenidyl and L-dopa: an electromyographic study with specific reference to tremor

An electromyographic method was used to study the effect of combination therapy with L-dopa and trihexyphenidyl on tremor in thirty patients suffering from extrapyramidal motor system disease. In this method tremor activity was measured and documented so that the course of the disease could be followed objectively. L-dopa alone was slightly more effective against tremor than was trihexyphenidyl alone. The combination of the two drugs was more effective than either drug used alone, and its side-effects were mild and definitely fewer than had been reported with L-dopa combined with a decarboxylase inhibitor. Good control of tremor with L-dopa and trihexyphenidyl was obtained clinically and verified electromyographically.