Ropinirole for the treatment of early Parkinson disease: a 12-month experience. Ropinirole Study Group

Comparative efficacy and safety of six non-ergot dopamine-receptor agonists in early Parkinson's disease: a systematic review and network meta-analysis

Background

Non-ergot dopamine agonists (NEDAs) have been used as monotherapy or as an adjunctive therapy to levodopa for many years. Novel long-acting formulations of NEDAs including pramipexole extended-release (ER), ropinirole prolonged-release (PR), and rotigotine transdermal patch have been developed. However, there is no strong evidence that a given NEDA is more potent than another. We performed a systematic review and network meta-analysis to evaluate the efficacy, tolerability and safety of six commonly used NEDAs in early Parkinson's disease (PD).

Methods

Six NEDAs including piribedil, rotigotine transdermal patch, pramipexole immediate-release (IR)/ER, and ropinirole IR/PR were investigated. The efficacy outcomes including Unified Parkinson's Disease Rating Scale activities in daily life (UPDRS-II), motor function (UPDRS-III), and their subtotal (UPDRS-II + III), tolerability and safety outcomes were analyzed.

Results

A total of 20 RCTs (5,355 patients) were included in the current study. The result indicated that compared with placebo, all six investigated drugs had statistically significant differences in the improvement of UPDRS-II, UPDRS-III, and UPDRS-II + III (except ropinirole PR in UPDRS-II). There were no statistically significant differences between six NEDAs for the UPDRS-II and UPDRS-III. For UPDRS-II + III, the improvement of ropinirole IR/PR and piribedil were higher than that of rotigotine transdermal patch, and piribedil was higher than that of pramipexole IR. The surface under the cumulative ranking curve (SUCRA) indicated that piribedil resulted in best improvement in UPDRS-II and UPDRS-III (0.717 and 0.861, respectively). For UPDRS-II + III, piribedil and ropinirole PR exhibited similar improvement and both had high rates (0.858 and 0.878, respectively). Furthermore, piribedil performed better as monotherapy, ranking first in the improvement of UPDRS-II, III, and II + III (0.922, 0.960, and 0.941, separately). With regard to tolerability, there was a significant increase in overall withdrawals with pramipexole ER (0.937). In addition, the incidence of adverse reaction of ropinirole IR was relatively high (nausea: 0.678; somnolence: 0.752; dizziness: 0.758; fatigue: 0.890).

Conclusions

In this systematic review and network meta-analysis of six NEDAs, piribedil exhibited better efficacy, especially as monotherapy, and ropinirole IR was associated with a higher incidence of adverse events in patients with early PD.

Identifying potential drug-target interactions based on ensemble deep learning

Introduction

Drug-target interaction prediction is one important step in drug research and development. Experimental methods are time consuming and laborious.

Methods

In this study, we developed a novel DTI prediction method called EnGDD by combining initial feature acquisition, dimensional reduction, and DTI classification based on Gradient boosting neural network, Deep neural network, and Deep Forest.

Results

EnGDD was compared with seven stat-of-the-art DTI prediction methods (BLM-NII, NRLMF, WNNGIP, NEDTP, DTi2Vec, RoFDT, and MolTrans) on the nuclear receptor, GPCR, ion channel, and enzyme datasets under cross validations on drugs, targets, and drug-target pairs, respectively. EnGDD computed the best recall, accuracy, F1-score, AUC, and AUPR under the majority of conditions, demonstrating its powerful DTI identification performance. EnGDD predicted that D00182 and hsa2099, D07871 and hsa1813, DB00599 and hsa2562, D00002 and hsa10935 have a higher interaction probabilities among unknown drug-target pairs and may be potential DTIs on the four datasets, respectively. In particular, D00002 (Nadide) was identified to interact with hsa10935 (Mitochondrial peroxiredoxin3) whose up-regulation might be used to treat neurodegenerative diseases. Finally, EnGDD was used to find possible drug targets for Parkinson's disease and Alzheimer's disease after confirming its DTI identification performance. The results show that D01277, D04641, and D08969 may be applied to the treatment of Parkinson's disease through targeting hsa1813 (dopamine receptor D2) and D02173, D02558, and D03822 may be the clues of treatment for patients with Alzheimer's disease through targeting hsa5743 (prostaglandinendoperoxide synthase 2). The above prediction results need further biomedical validation.

Discussion

We anticipate that our proposed EnGDD model can help discover potential therapeutic clues for various diseases including neurodegenerative diseases.

Recent advances in dopamine D2 receptor ligands in the treatment of neuropsychiatric disorders

Dopamine is a biologically active amine synthesized in the central and peripheral nervous system. This biogenic monoamine acts by activating five types of dopamine receptors (D_1-5 Rs), which belong to the G protein-coupled receptor family. Antagonists and partial agonists of D₂ Rs are used to treat schizophrenia, Parkinson's disease, depression, and anxiety. The typical pharmacophore with high D₂ R affinity comprises four main areas, namely aromatic moiety, cyclic amine, central linker and aromatic/heteroaromatic lipophilic fragment. From the literature reviewed herein, we can conclude that 4-(2,3-dichlorophenyl), 4-(2-methoxyphenyl)-, 4-(benzo[b]thiophen-4-yl)-1-substituted piperazine, and 4-(6-fluorobenzo[d]isoxazol-3-yl)piperidine moieties are critical for high D₂ R affinity. Four to six atoms chains are optimal for D₂ R affinity with 4-butoxyl as the most pronounced one. The bicyclic aromatic/heteroaromatic systems are most frequently occurring as lipophilic appendages to retain high D₂ R affinity. In this review, we provide a thorough overview of the therapeutic potential of D₂ R modulators in the treatment of the aforementioned disorders. In addition, this review summarizes current knowledge about these diseases, with a focus on the dopaminergic pathway underlying these pathologies. Major attention is paid to the structure, function, and pharmacology of novel D₂ R ligands, which have been developed in the last decade (2010-2021), and belong to the 1,4-disubstituted aromatic cyclic amine group. Due to the abundance of data, allosteric D₂ R ligands and D₂ R modulators from patents are not discussed in this review.

The effect and safety of ropinirole in the treatment of Parkinson disease: A systematic review and meta-analysis

BACKGROUND

It is necessary to conduct a meta-analysis of the clinical randomized controlled trials (RCTs) on ropinirole in the treatment of Parkinson disease (PD), to explore the effects and safety of ropinirole, and to provide a theoretical basis for clinically safe and rational drug use.

METHODS

RCTs on the effectiveness and safety of ropinirole in the treatment of PD were searched. We searched Dutch medical literature database, Pubmed, Cochrane Library, China National Knowledge Infrastructure, Wanfang Knowledge Service Platform up to December 15, 2020. The Cochrane risk bias assessment tool was used to evaluate the quality of the included literature, and the RevMan5.3 software was used for meta-analysis.

RESULTS

A total of 12 RCTs with 3341 patients were included. The changes of Parkinson Disease Rating Scale Part II score (mean difference = -2.23, 95% confidence interval [CI] -2.82 to -1.64) and Parkinson Disease Rating Scale Part III scores (mean difference = -4.93, 95%CI -5.25 to -4.61) in the ropinirole group was significantly lower than that in the control group. The incidence of dizziness (odd risk [OR] = 1.85, 95%CI 1.50-2.28), nausea (OR = 2.17, 95%CI 1.81-2.59), vomiting (OR = 2.73, 95%CI 1.47-5.09), and lethargy (OR = 2.19, 95%CI 1.39-3.44) in the ropinirole group was significantly higher than that in the control group (all P < .05), and there were no significant differences in the incidence of headache (OR = 1.14, 95%CI 0.79-1.65) and insomnia (OR = 1.06, 95%CI 0.72-1.55) were found between 2 groups (all P > .05).

CONCLUSIONS

Ropinirole can help improve the ability of daily living and exercise function of PD patients, but it will increase the incidence of related adverse reactions, which needs to be further confirmed by subsequent large-scale, high-quality RCTs.

Emerging Pharmacotherapies for Motor Symptoms in Parkinson's Disease

Parkinson's disease (PD) is the second commonest neurodegenerative disorder in the older adult and is characterized by progressive disabling motor symptoms of bradykinesia, tremor, rigidity, postural instability and also non motor symptoms that affect quality of life. The pharmacotherapy of PD consists of oral, transdermal, and subcutaneous medications, as well as invasive advanced therapies at later stages of the disease. PD medications are often started as monotherapy but with the progression of the illness often there is a need to add more medications and frequently comprises of a challenging polypharmacotherapy. Adverse effects of pharmacotherapy often add to the problems of adequate treatment. Patients and physicians have to prioritize treatment goals on the most disabling symptoms and the safest and most effective treatments. Almost every year newer medications and modes of delivery continue to be researched and added to the therapeutic armamentarium. This review article outlines existing and emerging pharmacotherapies for motor symptoms in PD.

Istradefylline to Treat Patients with Parkinson's Disease Experiencing "Off" Episodes: A Comprehensive Review

Parkinson’s disease (PD) is a common neurodegenerative disorder that leads to significant morbidity and disability. PD is caused by a loss of dopaminergic, cholinergic, serotonergic, and noradrenergic neurons in the central nervous system (CNS), and peripherally; the syndromic parkinsonism symptoms of movement disorder, gait disorder, rigidity and tremor are mostly driven by the loss of these neurons in the basal ganglia. Unfortunately, a significant proportion of patients taking levodopa, the standard of care treatment for PD, will begin to experience a decrease in effectiveness at varying times. These periods, referred to as “off episodes”, are characterized by increased symptoms and have a detrimental effect on quality of life and disability. Istradefylline, a novel adenosine A2A receptor antagonist, is indicated as a treatment addition to levodopa/carbidopa in patients experiencing “off episodes”. It promotes dopaminergic activity by antagonizing adenosine in the basal ganglia. This review will discuss istradefylline as a treatment for PD patients with off episodes.

Pharmacological Treatment of Early Motor Manifestations of Parkinson Disease (PD)

Parkinson disease (PD), as a slowly progressive neurodegenerative disorder, undergoes six neuropathological stages. The earliest clinical manifestation presents in the middle stage of the disorder pathologically, when 50% or more of the dopaminergic neurons have degenerated in the substantia nigra. This discrepancy between the early stage clinically and that pathologically has, in part, spurred the debate as to when it is best to initiate symptomatic therapy. The most well-studied monotherapeutic agents for PD in its early course include levodopa (the cornerstone of PD therapy), dopamine agonists, and monoamine oxidase inhibitors (MAOIs). With several options for initiating pharmacologic therapy, along with the heterogenous presentation of the disorder, an individualized approach is warranted. Careful deliberation must be done to optimize risk reduction while providing effective symptom control, taking the chronological age, comorbidities, social and financial disposition, work status, and both immediate- and long-term goals into consideration. Generally, treatment can be delayed in patients with mild symptoms and minimal functional impairment at any age. If treatment must be initiated, dopamine agonists and monoamine oxidase type B inhibitors can be used, especially in younger patients with milder disease. However, for older patients, those with moderate to severe PD symptoms, regardless of age, or for patients with greater comorbidities, levodopa generally remains the better choice. Eventually, regardless of initial therapy, studies have shown that most will eventually require levodopa therapy when symptoms become more disabling.

Comparison for Efficacy and Tolerability among Ten Drugs for Treatment of Parkinson's Disease: A Network Meta-Analysis

Parkinson’s disease (PD) is a long term disorder affects the central nervous system and we aim to determine the relative efficacy of the current available drugs used in PD. Firstly, we performed a systematic review in current literature and eligible studies were retrieved from online databases, relevant data were extracted. Efficacy of these medications was assessed by different Unified Parkinson’s Disease Rating Scales (UPDRS). Mean difference (MD) and odds ratio (OR) were produced by pairwise or network meta-analysis (NMA). Finally, we performed a cluster analysis for the included medications with respect to their surface under the cumulative ranking curve (SUCRA). Pairwise meta-analysis suggests that selegiline had a higher ranking in UPDRS II, UPDRS III and UPDRS total than bromocriptine and levodopa. Selegiline was more tolerable than bromocriptine (OR = 0.62, CI: 0.39 to 0.98) and pramipexole was less tolerable than levodopa (OR = 1.43, CI = 1.00 to 2.04). Results of NMA indicate that patients with levodopa, pramipexole, ropinirole and selegiline exhibited a significantly improved UPDRS III than those with lazabemide. To sum up, levodopa, selegiline, ropinirole and rotigotine were recommended for PD patients as they appeared relatively high efficacy and tolerability.

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.

Abnormal involuntary movement (AIM) expression following D2 dopamine agonist challenge is determined by the nature of prior dopamine receptor stimulation (priming) in 6-hydroxydopamine lesioned rats

Rats with unilateral 6-hydroxydopamine (6-OHDA) lesions show sensitization (priming) of rotational behavior upon repeated treatment with dopamine agonists. To relate these observations to dyskinesias exhibited by Parkinson's Disease patients, we assessed abnormal involuntary movements (AIMs) in 6-OHDA rats, which were primed with three injections of either the following: water, D1/D2 agonist apomorphine (Apo) (0.5mg/kg), D1 agonist SKF38393 (SKF) (10mg/kg) or D2 agonist quinpirole (Quin) (1 or 2.5mg/kg). The rats were challenged one week later with Quin (0.25mg/kg). Axial, limb, orolingual, locomotor, and grooming AIMs were scored (0-4) every 5min. Priming with water did not produce AIMs. Priming with Quin (1mg/kg) produced axial and locomotor AIMs, while priming with Apo, SKF or Quin (2.5mg/kg) produced axial, locomotor, limb, and grooming AIMs. The disparity in AIM profiles between Quin (1mg/kg) and (2.5mg/kg) was not the result of D1 receptor stimulation since there was little striatal Fos expression following the third priming injection with Quin (1 or 2.5mg/kg) compared to following SKF, which led to robust striatal Fos expression. Challenge with Quin (0.25mg/kg) essentially reproduced the categories of AIMs exhibited during priming, with no AIMs in water-primed 6-OHDA rats, mild, non-significant, axial and locomotor AIMs in Quin (1 and 2.5mg/kg)-primed 6-OHDA rats, and axial, limb, locomotor, and grooming AIMs in Apo- and SKF-primed 6-OHDA rats. These data suggest that the types of AIMs expressed following challenge with Quin depend on the dopamine receptor subtype and dose of dopamine agonist used during priming.

Duration of L-dopa and dopamine agonist monotherapy in Parkinson's disease

The expected duration of initial antiparkinson monotherapy before the need for supplementation is not clearly defined for routine practice. The aim of this study was to define the length of L-dopa (L-3, 4-dihydrophenylalanine) and dopamine agonist monotherapy. The duration of monotherapy and discontinuation rates were investigated in a natural observational setting by plotting Kaplan-Meier survival curves. Out of 345 patients, 180 (52.2%) received L-dopa and 165 (47.8%) received a dopamine agonist as initial monotherapy. Half of the patients starting L-dopa received supplementary therapy with- in 3.6 years (95% confidence interval, 3.2-4.6), significantly longer than for dopamine agonist monotherapy (half required a second agent at 2.3 years [2.0-2.9]; P = 0.00017). Discontinuation of L-dopa therapy was 1%. Dopamine agonists were stopped (due to side-effects like impulse control disorders [6%], somnolence [4%] and light-headedness [3%]) in 20% over four years. The duration and tolerability of L-dopa and dopamine agonists as initial Parkinson's disease monotherapy are defined in this study; this may form part of the information exchange with patients.

cAMP response element binding protein phosphorylation in nucleus accumbens underlies sustained recovery of sensorimotor gating following repeated D₂-like receptor agonist treatment in rats

BACKGROUND

Prepulse inhibition (PPI) is a cross-species measure of sensorimotor gating. PPI deficits are observed in humans and rats upon acute treatment with dopamine D₂-like receptor agonists and in patients with schizophrenia. Repeated treatment with a D₂-like agonist, however, reverses PPI deficits and increases cyclic adenosine monophosphate (cAMP) signaling in the nucleus accumbens (NAc). This study examined the short- and long-term effects on PPI of treatment with quinpirole and ropinirole, dopamine D₂/D₃ receptor agonists, and the molecular mechanism by which they occur.

METHODS

PPI was assessed in adult male Sprague-Dawley rats following acute and chronic treatment with quinpirole or ropinirole and 1, 2, 3, and 4 weeks after termination of repeated ropinirole treatment. Finally, the effect of dominant negative mutant cAMP response element binding protein (CREB) overexpression in the NAc on PPI following chronic quinpirole treatment was assessed.

RESULTS

Acute quinpirole produced dose-dependent PPI deficits, whereas ropinirole caused consistent PPI reduction at all but the highest dose. Repeated ropinirole treatment significantly increased PPI compared with acute treatment, and increased CREB phosphorylation in NAc neurons. Subsequent ropinirole challenge had no effect as long as 28 days later, at which time NAc CREB phosphorylation had normalized. Overexpression of dominant negative mutant CREB prevented PPI recovery induced by chronic quinpirole treatment.

CONCLUSIONS

Chronic quinpirole or ropinirole treatment produces sustained PPI recovery; CREB activity in the NAc is required to induce PPI recovery but not to maintain it. The results suggest that transcriptional regulation by CREB mediates long-lasting changes occurring within NAc circuits to promote recovery of sensorimotor gating.

Successful treatment of post-stroke apathy by the dopamine receptor agonist ropinirole

Dopamine D2/3 receptor agonists have been widely used to treat motor symptoms in Parkinson's disease and are also reported to improve cognitive and emotional disturbances. Here we describe a patient who developed severe apathy after cerebral infarction in the prefrontal cortex. After administration of ropinirole, his verbal output and spontaneity in daily life was improved remarkably. This improvement was associated with increased blood flow in the prefrontal cortex and basal ganglia. We suggest that ropinirole may be a treatment option for deficits in motivated behavior after prefrontal damage.

An Exploratory Retrospective Evaluation of Ropinirole-Associated Psychotic Symptoms in an Outpatient Population Treated for Restless Legs Syndrome or Parkinson's Disease

Background:

Traditional treatment approaches for the management of restless legs syndrome (RLS) and Parkinson's disease (PD) include the use of medications that either directly or indirectly increase dopamine levels. In turn, a potential adverse event that could be expected is the development or exacerbation of psychiatric-related symptoms.

Objective:

To evaluate and describe the incidence of psychosis and associated behavioral features in patients taking ropinirole for RLS or PD.

Methods:

Patients were identified from a computerized database search of outpatients being treated with ropinirole for 1 of 2 medical conditions: PD or RLS. Data were collected in a retrospective manner from 95 patients who were tracked over the course of their therapy to determine whether psychosis or associated behavioral symptoms developed as a result and whether an intervention was needed to adjust ropinirole dosing or if additional medications had to be added to control features associated with psychosis.

Results:

A total of 284 patients being treated for RLS or PD were identified; of this group, 95 patients were identified as being treated for PD or RLS with ropinirole. Of the 95 patients being treated with ropinirole, 13 developed psychotic features that required therapeutic intervention with either the use of an antipsychotic or dose adjustment of ropinirole. PD patients included in this study were numerically more likely to develop psychotic features compared with RLS patients; however, the difference was not statistically significant (p = 0.122). The results do suggest that this risk is increased when ropinirole is used as part of a dual therapy approach with dopamine agonists in the treatment of either PD or RLS (p = 0.003).

Discussion:

Dopamine agonists have long been used as preferred treatment in the management of PD and RLS. When treating either PD or RLS in the psychiatric population, the concern arises that increased activity at dopamine receptors may induce or exacerbate psychiatric features. A potential clinical concern with the use of ropinirole is the potential for patients to develop psychiatric features, although there are few data available to demonstrate whether stimulation of targeted individual dopamine receptors is linked to the development or exacerbation of psychotic features. It is also undetermined whether concurrent antipsychotic treatment provides any protective benefit against psychosis, especially in patients already being treated for psychotic symptoms.

Conclusions:

Our findings suggest that ropinirole may play a role in inducing or exacerbating psychosis and its associated features, although a number of confounding variables prevent the determination of a clear association and suggest that further investigation is warranted in controlled clinical trials.

Impact of newer pharmacological treatments on quality of life in patients with Parkinson's disease

Parkinson's disease is a common progressive neurodegenerative condition with multiple motor and nonmotor features contributing to impairment of health-related quality of life (HR-QOL). Pharmacological treatments have been directed primarily at dopamine replacement with levodopa and agents to improve its bioavailability, including DOPA decarboxylase inhibitors, catechol-O-methyltransferase (COMT) inhibitors and monoamine oxidase B (MAO-B) inhibitors, as well as synthetic dopamine agonists. These treatments to restore motor function are often very successful in early Parkinson's disease, with objective improvement and concomitant improvement in subjective HR-QOL scores. However, as the disease progresses, motor complications and nonmotor symptoms predominate and are often refractory to therapeutic interventions. Antiparkinsonian medications have been shown to improve motor severity and motor complications of advancing disease, and there is increasing evidence that this can be translated into subjective improvement of HR-QOL from a patient's point of view. However, the degree of improvement is less marked on HR-QOL scores than on motor scores, and some studies do not show improvement of HR-QOL in parallel to motor improvements. A number of explanations are possible, including limitations of the scales used, trial designs and lack of clinical improvement from the patients' point of view. This review concentrates on clinical trials with an index of HR-QOL as an outcome measure, with particular emphasis on well designed, randomized, double-blind, placebo-controlled or active comparator-controlled methodology. Drugs that have been more recently added to the armamentarium of Parkinson's disease, including the oral (pramipexole, ropinirole and piribedil) and transdermal (rotigotine) non-ergotamine-derived dopamine agonists, the novel MAO-B inhibitor rasagiline and the COMT inhibitors tolcapone and entacapone, were included. The effect of each of these agents on overall HR-QOL and depression, a factor that has been shown to significantly contribute to HR-QOL in several multivariate analyses, is discussed.Overall, the literature search revealed 14 double-blind, placebo- or active comparator-controlled trials with an index of HR-QOL as an outcome measure. Entacapone resulted in HR-QOL improvement in nonfluctuating patients (one study) but not clearly in those with motor fluctuations (two studies). Tolcapone was only tested in patients with motor fluctuations and resulted in significant improvement in two of four studies using HR-QOL as an outcome measure. Rasagiline improved HR-QOL as monotherapy in early Parkinson's disease (one study), but not clearly in more advanced disease (one study). Rotigotine improved HR-QOL in both early Parkinson's disease (one study) and more advanced disease with motor fluctuations (one study). The impact of ropinirole and pramipexole on HR-QOL as monotherapy in early Parkinson's disease versus placebo has not been assessed, but both agents have resulted in improved HR-QOL in patients with motor fluctuations (ropinirole one study, pramipexole one study). The evidence for antidepressant efficacy of antiparkinsonian medications is limited.

Discontinuation of ropinirole and pramipexole in patients with Parkinson's disease: clinical practice versus clinical trials

OBJECTIVE

To compare characteristics and incidence of discontinuation of Parkinson's disease (PD) patients starting ropinirole or pramipexole in clinical practice with data from randomised controlled clinical trials (RCTs).

METHODS

Included in the retrospective clinical-practice cohort were first-time users of ropinirole or pramipexole diagnosed with PD before 2005. Baseline characteristics and incidence of discontinuation were compared between the clinical-practice cohort and RCTs. Treatment discontinuation was defined as more than 180 days between two refills of ropinirole or pramipexole. The incidence of discontinuation in RCTs was based on the reported rate of discontinuation for any cause.

RESULTS

Included were 45 patients who started with ropinirole and 59 patients who started with pramipexole. Treatment was discontinued within 3 years in 51% (ropinirole) and 60% (pramipexole) of the patients. Ten RCTs with ropinirole and 12 with pramipexole were identified. Baseline characteristics did not differ between the clinical-practice cohort and RCTs. RCTs reported discontinuation rates comparable with those at the same timepoint in the clinical practice until 1 year of follow-up.

CONCLUSION

This study shows that the overall incidence of discontinuation of ropinirole and pramipexole between the patients in our clinical-practice cohort and patients in the RCTs was comparable for the short term. However for the long term, discontinuation in practice is possibly higher.

Current status of symptomatic medical therapy in Parkinson's disease

Symptomatic medical therapies for Parkinson's disease (PD) have been disease modifying and have led to improvement in daily function, quality of life, and survival. For 40 years, these therapies have been primarily dopaminergic, and currently include the dopamine (DA) precursor levodopa (LD), DA agonists, catechol-O-methyltransferase (COMT) inhibitors, and monoamine oxidase (MAO) inhibitors. The roles of all these classes of agents have evolved, with significant changes occurring since the early 2000s. This article reviews the current literature for each of these classes of drugs, with a focus on efficacy and place in the therapeutic scheme. Levodopa is no longer considered to be toxic and, thus, its early use is not only appropriate but recommended. Ergot agonists are no longer in use, and new agents administered in patch form or subcutaneous injections have been approved. The COMT inhibitor tolcapone, with its significant efficacy, has been reintroduced, and two new MAO inhibitors have been approved. Selected safety issues are discussed, including the incidence of melanoma in relation to LD; pathological gambling and DA agonists; hepatic toxicity of tolcapone; and the tyramine or so-called cheese reaction with MAO B inhibitors. The article closes with a discussion of future directions and new drugs under development.

Clinical studies with ropinirole in Parkinson's disease and RLS

Ropinirole is a modern dopamine agonist with a half-life of medium extent that is highly selective for D(2)-receptors. Ropinirole is an indole derivative and thus does not belong to the group of ergoline dopamine receptor agonists. Its effect has been proved in a number of controlled studies in both monotherapy and combination treatments of Parkinson's disease. We can meanwhile refer to the long-term data of studies that have been run for more than 10 years. The substance has also been approved for the management of restless legs syndrome. A long-acting formula of the substance will be available soon.

Overexpression of D2/D3 receptors increases efficacy of ropinirole in chronically 6-OHDA-lesioned Parkinsonian rats

Ropinirole, which is a non-ergot dopamine agonist derivative, exerts therapeutic benefits in Parkinson's disease (PD). Based on recent studies implicating dopamine receptors 2 and 3 (D2R and D3R) as possible targets of ropinirole, we over-expressed these dopamine receptor genes in the dopamine-denervated striatum of rodents to reveal whether their over-expression modulated ropinirole activity. Adult Sprague-Dawley rats initially received unilateral 6-hydroxydopamine lesion of the medial forebrain bundle. At 1 month after surgery, successfully lesioned animals (3 or less forelimb akinesia score, and 8 or more apomorphine-induced rotations/min over 1 h) were randomly assigned to intrastriatal injection (ipsilateral to the lesion) of blank lentiviral vector, D2R, D3R or both genes. At about 5 months post-lesion, ropinirole (0.2 mg/kg, i.p.) was administered daily for 9 consecutive days. The subtherapeutic dose of ropinirole improved the use of previously akinetic forelimb and produced robust circling behavior in lesioned animals with striatal over-expression of both D2R and D3R compared to lesioned animals that received blank vector. In contrast, the subtherapeutic dose of ropinirole generated only modest motor effects in lesioned animals with sole over-expression of D2R or D3R. Western immunoblot and autoradiographic assays showed enhanced D2R and D3R protein levels coupled with normalized D2R and D3R binding in the ventral striatum of lesioned animals with lentiviral over-expression of both D2R and D3R relative to vehicle-treated lesioned animals. Immunohistochemical analyses showed that D2R and D3R GFP fluorescent cells colocalized with enkephalin and substance P immunoreactive medium spiny neurons. These data support the use of the subtherapeutic dose of ropinirole in a chronic model of PD.

Ropinirole, a non-ergoline dopamine agonist

Dopamine agonists have become indispensable in the treatment of Parkinson's disease. In every-day practice, however, the decision to select the best compound for an individual patient is rendered difficult because of the large number of substances available on the market. This review article provides a closer look at the experimental and clinical studies with ropinirole published so far. Ropinirole is a non-ergoline dopamine agonist which has been proven to be effective in both, monotherapy and combination therapy of idiopathic Parkinson's disease. In addition to ameliorating bradykinesia, rigor, and tremor, ropinirole facilitates the daily life and improves depressive moods of patients with Parkinson's disease. The long-term complications of levodopa are avoided, and problems commonly associated with levodopa treatment are reduced. Ropinirole appears to have a neuroprotective effect. In addition to Parkinson's disease, ropinirole has also been used successfully in the treatment of restless legs syndrome.

Ropinirole in the treatment of Parkinson's disease

In this review, the pharmacokinetics, safety and tolerability, and clinical efficacy of ropinirole (Requip), a non-ergoline dopamine agonist approved for use in the treatment of Parkinson's disease (PD) are examined. A summary of preclinical and clinical studies is presented. Ropinirole is safe and efficacious as monotherapy in the treatment of early PD and as an adjunct to levodopa in more advanced cases.

Comparison of the risk of adverse events with pramipexole and ropinirole in patients with Parkinson's disease: a meta-analysis

BACKGROUND

Pramipexole and ropinirole are relatively new dopamine agonists, both of which have proven efficacy in the treatment of Parkinson's disease. There is, however, uncertainty regarding differences in the adverse event profiles associated with each drug.

OBJECTIVE

To compare the adverse events of pramipexole and ropinirole as reported in the peer-reviewed medical literature.

METHODS

We systematically reviewed the medical literature to identify randomised controlled trials of pramipexole and ropinirole used in the management of Parkinson's disease. Computerised databases (including Medline, Embase, the Cochrane Library, and the International Pharmaceutical Abstracts) were used to identify pertinent articles for inclusion in this study. Trials that compared the dopamine agonists to either levodopa or placebo were included.

ANALYSIS

Adverse events with these drugs included dizziness, nausea, hypotension, hallucinations, and somnolence. We made two separate analyses. In the first analysis, we estimated the pooled relative risk (RR) of adverse events with either pramipexole or ropinirole as compared with levodopa. In the second analysis, the pooled RRs of adverse events with pramipexole and ropinirole were compared with placebo. We used the random-effects model of DerSimonian and Laird to estimate the RRs and their corresponding 95% CIs. We tested for study heterogeneity using Q statistics.

RESULTS

There was no significant difference in the risk of dizziness, nausea, or hypotension with either drug individually or in combination when compared with levodopa. The risk of hypotension was approximately four times higher with ropinirole than pramipexole when each drug was individually compared with placebo (6.46 [95% CI 1.47-28.28] for ropinirole, and 1.65 [0.88-3.08] for pramipexole). The pooled RR (for pramipexole and ropinirole combined) of hallucinations was 1.92 (95% CI 1.08-3.43) when compared with levodopa. Relative to placebo, pramipexole had a significantly higher risk of hallucinations than ropinirole (pramipexole 5.2 [95% CI 1.97-13.72] vs ropinirole 2.75 [95% CI 0.55-13.73]). There was no significant difference in the risk of somnolence between the two drugs when each was individually compared with levodopa. When compared with placebo, the pooled RR (pramipexole and ropinirole combined) of somnolence was 3.16 (95% CI 1.62-6.13). Relative to placebo, the risk of somnolence was 2.01 (95% CI 2.17-3.16) with pramipexole and 5.73 (95% CI 2.34-14.01) with ropinirole.

CONCLUSIONS

Use of ropinirole seems to be associated with a higher risk of hypotension and somnolence than use of pramipexole when compared with placebo. Use of pramipexole seems to be associated with a higher risk of hallucinations than use of ropinirole when compared with placebo.

Advances in the pharmacological management of Parkinson disease

Numerous advances have taken place in the pharmacological management of Parkinson disease (PD) in recent years. Some of the more clinically relevant will be discussed in the text that follows. New drugs have been developed to treat or prevent the motor fluctuations and dyskinesias that occur frequently with the continuous use of levodopa. Such drugs include the catechol-O-methyl-transferase (COMT) inhibitors, such as tolcapone and entecapone, and new dopamine (DA) agonists with long half lives such as cabergoline, pramipexole or ropirinole. Also new, atyical, antipsychotics have appeared which have revolutionized the treatment of PD since they allow us to control hallucinations and other psychotic behaviour without worsening of motor function. Finally preliminary reports suggest that cholinesterase inhibitors, such as rivastigmine, can be usefull in the management of cognitive impairment in PD, one of the most difficult clinical problems encountered in the management of this neurodegenerative disorder.

'Sleep attacks' or 'unintended sleep episodes' occur with dopamine agonists: is this a class effect?

Controversial reports of sudden onset 'sleep attacks' resulting in road traffic accidents have recently been reported in patients with Parkinson's disease (PD) taking the non-ergot dopamine D(2 )/D(3) receptor agonists pramipexole and ropinirole. These reports have generated considerable debate as the concept of 'sleep attacks' is disputed amongst sleep specialists and most believe that isolated 'sleep attacks' not preceded by warning on the background of chronic sleepiness or 'unintended sleepiness' do not exist. A series of case reports suggested that this phenomenon may not be exclusive to the non-ergot dopamine agonists such as pramipexole or ropinirole and indeed may occur with most dopaminergic agents. Recent evidence suggest that a 'sleepiness' or 'hypoactivity' reaction to dopaminergic therapy may be related to underlying dopamine deficiency of PD rather than a drug effect. In this report we provide the evidence for the phenomenon being a class effect attributable to all dopamine agonists currently employed in the management of PD. Controversy surrounding excessive daytime sleepiness (EDS) in PD and the use of the Epworth Sleepiness Scale (ESS) in relation to PD is also discussed. In spite of variable reports, EDS is recognised to be common in PD and is likely to be related to both the disease process and drug therapy. Studies using multiple sleep latency tests have also reported differing results in PD although a recent study indicated that a subset of 'sleepy' patients with PD may experience pathological somnolence with resultant detrimental consequence on daytime and cognitive functions. We recommend that the issue of 'sleepiness' or 'sleep attacks' in PD should be routinely checked in all patients with PD and indirectly assessed by using either the ESS or the recently introduced Parkinson's Disease Sleep Scale. Those with reported 'sleep attacks' or 'unintended sleep episodes' and excessive daytime sleepiness while taking dopamine agonists or dopaminergic agents such as levodopa should have a review of their medication, should not be driving a car on their own and some may merit formal sleep architecture studies. The latter may identify sleep disorders such as secondary narcolepsy which may benefit from the use of a wakefulness promoting agent.

Excessive daytime sleepiness in de novo and treated Parkinson's disease

Excessive daytime sleepiness (EDS) in Parkinson's disease (PD) is due to either treatment-related factors or the disease itself. The study of this disturbing phenomenon in de novo parkinsonian patients may contribute to a better understanding of its pathophysiology. We conducted a case control study in which we compared 25 PD patients who had never been treated before with dopaminergic drugs (de novo PD), 50 PD patients being treated with dopaminergic drugs (treated PD), and 25 healthy control subjects, all of whom were matched for age and gender. EDS was measured by means of the Epworth Sleepiness Scale (ESS) and quality of sleep by means of the Pittsburgh Sleep Quality Index (PSQI). ESS and PSQI scores were not statistically different between de novo PD patients and controls, whereas they were significantly higher in treated PD. Differences in ESS score variability were best explained by the treatment effect, whereas there was no clear correlation between PSQI and any of the clinical variables considered.

Frontiers in Neuropharmacotherapy Part II: Multiple Sclerosis and Parkinson’s Disease

Disease-modifying agents such as β-interferons and glatiramer acetate have a significant impact on slowing the course of relapsing-remitting multiple sclerosis (MS). Therapeutic guidelines recommend initiating therapy with 1 of the 3 agents shortly after diagnosis of clinically definite MS, but there is insufficient data to specifically select one of the therapies. New research helps differentiate the therapies based on their induction of neutralizing antibodies, optimal dosing, and monitoring strategies. New treatments for secondary progressive MS are also emerging with evidence for the use of interferon β-1b and the approval of mitoxantrone. Future therapies for MS include oral glatiramer acetate and combination therapy.

Levodopa continues to be the standard of care for the treatment of Parkinson’s disease, but the approval of newer therapies that spare the use of levodopa and improve safety profiles are changing the management of the disease. Dopamine agonists such as bromocriptine and pergolide have been used to manage complications of levodopa therapy in patients with advanced disease, but new research supports the use of the more selective dopamine agonists, pramipexole and ropinirole, as monotherapy in early Parkinson’s disease. The combination of a catechol-O-methyltransferase (COMT) inhibitor with levodopa provides a new therapeutic option for treating patients with motor complications in advanced disease.

Evaluation of sleep and driving performance in six patients with Parkinson's disease reporting sudden onset of sleep under dopaminergic medication: a pilot study

Six patients with Parkinson's disease (PD) reporting unusually fast or sudden onset of sleep under the addition of dopamine agonists to a previous levodopa-containing therapy were examined using a sleep-wake diary, the Epworth sleepiness scale (ESS), polysomnography, multiple sleep latency tests (MSLT), a standardized vigilance test, and driving simulation. In all patients, ESS scores were increased and polysomnography showed disruption of the sleep pattern, a tendency towards poor sleep efficiency, and reduced proportions of slow- wave and rapid eye movement sleep. Pathological results in the MSLT or the vigilance test were obtained in five cases. For evaluation of driving performance, the standard deviation from the mean lane position during driving simulation was calculated. Three of five patients had clearly increased mean SDLP values. With respect to the measurement of daytime sleepiness (ESS, MSLT, vigilance test, and driving simulation), each patient had pathological results in at least two of these examinations. However, only a limited transfer of the routine vigilance assessment to driving performance was possible. In summary, this pilot study indicates that unusually fast or sudden onset of sleep in PD patients is a phenomenon of daytime sleepiness.

Increased risk of somnolence with the new dopamine agonists in patients with Parkinson's disease: a meta-analysis of randomised controlled trials

BACKGROUND

Recent case reports and letters have alerted practitioners to the risk of sleep attacks, usually preceded by somnolence, in patients with Parkinson's disease treated with pramipexole and ropinirole.

OBJECTIVE

To quantify the risk of somnolence with the new dopamine agonists pramipexole and ropinirole in patients with Parkinson's disease.

METHODS

We searched MEDLINE, EMBASE, International Pharmaceutical Abstracts and Cochrane Library, contacted experts and pharmaceutical manufacturers, and manually reviewed all references retrieved to identify possible articles to include. Information on randomisation, blinding, type of treatment and reporting of somnolence were abstracted by 2 independent reviewers. Disagreements were resolved by a third author.

ANALYSIS

We made 2 separate analyses. The first analysis compared the risk of somnolence in patients taking either pramipexole or ropinirole to that in patients taking placebo. The second analysis compared the risk of somnolence with these drugs (plus levodopa) versus that with levodopa alone. We calculated pooled relative risk estimates using the random effects model and when no heterogeneity was detected we used the fixed effects model.

RESULTS

Four trials were included in the analysis of patients taking pramipexole or ropinirole compared with those taking placebo. The pooled relative risk of somnolence in this analysis was 4.98 [95% confidence interval (CI) 1.79 to 13.89]. Seven trials were included in the analysis of patients taking levodopa and pramipexole or ropinirole compared with those taking levodopa alone. The pooled relative risk was 2.06 (95% CI 1.47 to 2.88).

CONCLUSION

Patients with Parkinson's disease using pramipexole or ropinirole are at higher risk of experiencing somnolence relative to patients taking placebo. Patients taking levodopa plus either one of these dopamine agonists are at higher risk than those taking levodopa alone. Clinicians should carefully weigh this risk against the benefit of these agents when prescribing these drugs.

Daytime somnolence in patients with Parkinson's disease

We studied daytime sleepiness in 160 patients with Parkinson's disease and 40 normal subjects. We compared the prevalence of daytime sleepiness in patients who were taking levodopa alone, levodopa with bromocriptine, levodopa with ropinirole, and levodopa with pramipexole. We found that (1) all these anti-Parkinson drugs can cause daytime sleepiness; (2) 'dozing off' correlated highly with 'falling asleep without warning'; (3) after statistical adjustment for confounding variables there was no significant difference among the risks for any of these anti-Parkinson drugs causing daytime somnolence.

Initial treatment of early Parkinson's disease: a review of recent, randomized controlled trials

Many studies have shown dopamine agonists to significantly improve parkinsonian symptoms compared with placebo in early Parkinson's disease (PD), but how do agonists compare with the standard treatment of levodopa? Recently, three large, multicenter, randomized controlled studies directly comparing a dopamine agonist with levodopa as initial therapy in early PD have been published. These studies suggest that although both agents effectively ameliorate parkinsonian symptoms, levodopa was superior to dopamine agonists as measured by improvement in Unified Parkinson's Disease Rating Scale (UPDRS) scores. However, levodopa was more frequently associated with dopaminergic motor complications, and the dopamine agonists were more commonly associated with adverse events. Until further studies clearly demonstrate the beneficial effects of one therapeutic strategy over another, the decision to initiate treatment in early PD with either an agonist or levodopa will be based on the favorable motor complication profile of agonists versus the more potent antiparkinsonian effects and the favorable side-effect profile of levodopa.

Treatment of early Parkinson's disease

Levodopa is still the most effective therapeutic agent for the treatment of Parkinson's disease (PD). Initially, levodopa provides a stable therapeutic response but, during long-term treatment its beneficial effect declines and a gradually increasing number of patients experience fluctuations in motor response. Therefore, in the management of PD it is important to minimise the risks for the development of motor fluctuations. In this context, recent double-blind long-term studies have confirmed the earlier results, suggesting that it appears advisable to initiate dopaminergic treatment in early PD by initially using a dopamine agonist and by adding levodopa when the benefit is no longer adequate with dopamine agonist alone. Another alternative would be to start with selegiline alone, then depending on the disability of the patient, add a dopamine agonist and finally levodopa.

Comparative pharmacological study of ropinirole (SKF-101468) and its metabolites in rats

The dopamine receptor agonist ropinirole (SKF-101468) is used to treat Parkinson's disease. Ropinirole is metabolized by two routes to a series of different metabolites although the predominant pathway is species-dependent. It is unknown whether any of the metabolites contribute to its antiparkinsonian activity and whether D3 or D2 receptor agonist activity plays a preferential role. Therefore ropinirole and its primary metabolites, SKF-104557, SKF-97930 and SKF-96990, and the rat metabolite, SKF-89124 were tested in the 6-hydroxydopamine lesion model of Parkinson's disease. SKF-89124 and SKF-96990 were also assayed in radioligand binding and microphysiometer functional assays at cloned human dopamine D2 and D3. Ropinirole and SKF-89124 were equipotent in-vivo, and produced dose-related increases in circling at 0.05-0.8 mg kg(-1), s.c. (ropinirole) and 0.05-0.75 mg kg(-1), s.c. (SKF-89124). Neither SKF-96990 or SKF-97930, at doses up to 15 mg kg(-1), increased the circling rate. Some circling was observed with 15 mg kg(-1) SKF-104557 but the response was less than half that produced by ropinirole (0.8 mgkg(-1)). SKF-104557 was 150-fold less potent than ropinirole. SKF-89124 possessed-30-fold higher affinity for D3 over D2 receptors in radioligand binding studies, but was not selective in the functional microphysiometer assay. SKF-96990 was 10-fold selective for D3 over D2 receptors in the radioligand binding assay. Ropinirole and SKF-104557 are 20-fold selective for D3 over D2 receptors in radioligand binding assays whereas in microphysiometry, selectivity is 10-fold. SKF-97930 is inactive in radioligand binding and microphysiometer assays. Primary metabolites of ropinirole did not contribute significantly to its activity in this model of Parkinson's disease. The lack of dopamine D3/D2 receptor selectivity for ropinirole rules out the possibility of attributing the degree of either D2 or D3 receptor activity to the behavioural efficacy of ropinirole.

Pramipexole-induced somnolence and episodes of daytime sleep

Pramipexole is a non-ergot dopamine agonist used to treat Parkinson's disease (PD). Because of concern regarding driving safety, we evaluated the incidence and nature of somnolence experienced by patients receiving pramipexole in clinical trials at our center. A retrospective chart review was performed and structured interviews were conducted with patients who had reported moderate or severe somnolence. In addition, two patients underwent polysomnography (PSG) and multiple sleep latency tests (MSLT) while on and 2 weeks after discontinuation of pramipexole. Forty patients with PD participating in pramipexole clinical trials were identified. In the double-blind phases of the studies, 22 patients were randomized to pramipexole and 18 were randomized to placebo. Six patients assigned to pramipexole reported somnolence as an adverse event (1 moderate, 5 mild) compared with two patients assigned to placebo (1 severe, 1 moderate; p = 0.19, one-tailed Fisher's exact test). Thirty-seven patients participated in open-label extension studies. Twenty-one (57%) reported somnolence as an adverse event. Eleven (30%) patients reported moderate somnolence and three (8%) patients reported severe somnolence. For patients with moderate or severe somnolence, the onset of worst-reported somnolence occurred at a mean (+/- standard error) pramipexole dose of 4.0 +/- 0.4 mg (range, 0.75-4.5 mg) per day. Patients had been taking pramipexole for a total of 10.0 +/- 1.5 months (range, .03-22 mos) and at their maximal dose for 6.7 +/- 1.5 months (range, .03-20 mos). During structured interviews with 12 of the 14 patients reporting moderate or severe somnolence, seven reported falling asleep while driving and two reported minor motor vehicle accidents caused by falling asleep. Most patients reported relatively continuous drowsiness that led to falling asleep without acute warning during periods of inactivity. Three patients reported discreet waves of irresistible sleepiness heralded by prodromal symptoms occurring against a background of normal wakefulness. MSLT in two of these patients revealed decreased latency to sleep without early onset of rapid eye movements. Sleep latency normalized after withdrawal of pramipexole. Intensive patient education is necessary to prevent motor vehicle accidents in patients taking pramipexole. We recommend that patients who are experiencing generalized drowsiness and falling asleep during periods of inactivity be instructed not to drive because these patients do fall asleep without acute warning. Somnolence usually resolves with pramipexole dose reduction or discontinuation. Patients should also be alerted to pull over and stop driving immediately if they feel a wave of sleepiness coming on. Patient education and compliance are critical to maximize safety.

Ropinirole: a review of its use in the management of Parkinson's disease

Ropinirole, a non-ergoline dopamine agonist, has selective affinity for dopamine D2-like receptors and little or no affinity for non-dopaminergic brain receptors. Ropinirole is indicated as adjunct therapy to levodopa in patients with advanced Parkinson's disease. It is also indicated, and recent clinical trials have focused on its use, as monotherapy in patients with early Parkinson's disease. In the symptomatic treatment of early Parkinson's disease ropinirole monotherapy was significantly more effective than placebo in 2 multicentre, randomised, double-blind trials of 3 to 12 months duration as assessed by the Unified Parkinson's Disease Rating Scale (UPDRS) motor scores and Clinical Global Impression/Clinical Global Evaluation Scales. In a similarly designed 3-year comparative study with bromocriptine, ropinirole recipients showed a significant improvement in UPDRS- activities of daily living (ADL) scores; however, motor scores were similar between the 2 groups. Ropinirole and levodopa treatments were similar in efficacy as measured by UPDRS ADL scores, although ropinirole recipients showed significantly less improvement on UPDRS motor scores at the 5-year study end-point in a multicentre, randomised double-blind trial. As an adjunct therapy to levodopa in patients with more advanced Parkinson's disease, ropinirole was reported to be as effective as bromocriptine and significantly more effective than placebo. In general in the comparisons with placebo ropinirole allowed a > or =20% reduction in the concomitant dose of levodopa without compromising efficacy in a significant proportion of patients and, in some trials decreased the amount of awake time spent in the 'off' state ('off' state is defined as a gradual return to parkinsonism despite adequate medication). Ropinirole was well tolerated either as monotherapy or as an adjunct to levodopa treatment. Nausea, dizziness and somnolence were the most commonly reported adverse events and were reported at a higher incidence by patients receiving ropinirole than by those receiving placebo. In patients with early Parkinson's disease, ropinirole generally showed a similar overall tolerability profile to bromocriptine although, over a 3-year period nausea was more commonly reported with ropinirole recipients. In a 5-year study, the incidence of dyskinesia was significantly lower with ropinirole than with levodopa regardless of levodopa supplementation. Prior to the addition of supplementary levodopa 5% of ropinirole recipients had experienced dyskinesia compared with 36% of those receiving levodopa.

CONCLUSIONS

In patients with early Parkinson's disease, ropinirole monotherapy was more efficacious than bromocriptine with regard to improvement in activities of daily living, and need for supplemental levodopa. Ropinirole recipients had a higher requirement for levodopa supplementation than levodopa recipients in a 5-year study, but the incidence of dyskinesia was significantly lower with ropinirole than with levodopa (markedly so in the one third of ropinirole recipients who were able to remain on monotherapy with no levodopa supplementation). Thus available data suggest that ropinirole may provide a means of treating early Parkinson's disease while minimising the risk of dyskinesia and delaying the need for supplemental levodopa in some patients. In addition, ropinirole is also efficacious in the management of more advanced Parkinson's disease in patients who are experiencing motor complications after long term levodopa use.

Comparative tolerability of the newer generation antiparkinsonian agents

In recent years, the treatment of Parkinson's disease has undergone an immense amount of research, resulting in the development of multiple new medications. This has largely been fuelled by dissatisfaction over the development of motor complications secondary to long term levodopa therapy. Different treatment approaches are applied depending on the stage of Parkinson's disease. In early and mild Parkinson's disease, selegiline offers a limited symptomatic effect. Its neuroprotective effect, although at present theoretical, has questionable clinical relevance. Increased mortality associated with selegiline has been reported, although a meta-analysis of 5 different trials did not support this finding. The newer, non-ergoline dopamine agonists, pramipexole and ropinirole, have undergone extensive studies to evaluate their efficacy as monotherapy in early Parkinson's disease. These newer agonists are ideal initial symptomatic medications, primarily because they delay the onset of levodopa-induced motor fluctuations. Efficacy of the newer dopamine agonists in advanced disease seems to be comparable to that of the older agents, bromocriptine and pergolide. Adverse effects can be reduced by starting the medication at a very low dose and then slowly titrating upward. Catechol-O-methyl transferase (COMT) inhibitors are indicated for the treatment of motor fluctuations in advanced disease, particularly the 'wearing-off' phenomenon. Tolcapone, a peripheral and central COMT inhibitor, appears to be quite effective, producing a 47% reduction in 'off' time. Unfortunately, 3 deaths have been observed, which are presumably secondary to tolcapone therapy. The drug has been withdrawn in many countries, and liver enzyme testing is mandatory in the US. Entacapone, a purely peripheral COMT inhibitor with a lower potency than tolcapone, has also proved to be effective and has not been associated with liver damage, obviating the need for testing.

The initial treatment of Parkinson's disease should begin with levodopa

For over two decades controversy has surrounded the initial choice of therapeutic agent for patients with early symptomatic Parkinson's disease. Whether levodopa or dopamine receptor agonist monotherapy in these patients is more efficacious and/or results in fewer long-term complications of dopaminergic therapy such as motor fluctuations, dyskinesias, or psychiatric disorders is unresolved. This article examines the evidence related to levodopa-sparing strategies and levodopa-induced toxicity in Parkinson's disease. At this time, there is little evidence to support levodopa-sparing strategies or to suggest that levodopa is toxic and harmful to patients with Parkinson's disease.

Treatment of Parkinson's disease should begin with a dopamine agonist

The occurrence of side effects with long-term levodopa therapy, such as fluctuations in motor performance or abnormal movements, led to a search for new antiparkinsonian drugs. Dopamine agonists include ergot derivatives such as bromocriptine, lisuride, pergolide, and cabergoline and other agents which do not possess the ergot structure such as pramipexole and ropinirole. They all are powerful stimulators of the D2 dopamine receptor which probably underlies their therapeutic effects. The clinical consequences of their binding to other dopamine receptor subtypes (D1 or D3) remains unknown. They are usually prescribed in combination with levodopa when late side effects begin to occur. This review summarizes the available pharmacologic and clinical data to support the early use of dopamine agonists in Parkinson's disease. Several strategies can be used, such as monotherapy or "early" or "late" combination with levodopa. Results of recent well-performed, modern clinical trials show that early use of the new dopamine agonists is able to effectively control the clinical symptoms for more than 3 years thereby offering the possibility of delaying the occurrence of levodopa-induced late motor side effects.