Multicenter, placebo-controlled trial of cabergoline taken once daily in the treatment of Parkinson's disease

Comparative effectiveness of dopamine agonists and monoamine oxidase type-B inhibitors for Parkinson's disease: a multiple treatment comparison meta-analysis

PURPOSE

To investigate the comparative effectiveness of dopamine agonists and monoamine oxidase type-B (MAO-B) inhibitors available for treatment of Parkinson's disease.

METHODS

We performed a systematic literature search identifying randomized controlled trials investigating 4 dopamine agonists (cabergoline, pramipexole, ropinirole, rotigotine) and 3 MAO-B inhibitors (selegiline, rasagiline, safinamide) for Parkinson's disease. We extracted and pooled data from included clinical trials in a joint model allowing both direct and indirect comparison of the seven drugs. We considered dopamine agonists and MAO-B inhibitors given as monotherapy or in combination with levodopa. Selected endpoints were change in the Unified Parkinson's Disease Rating Scale (UPDRS) score, serious adverse events and withdrawals. We estimated the relative effectiveness of each dopamine agonist and MAO-B inhibitor versus comparator drug.

RESULTS

Altogether, 79 publications were included in the analysis. We found all the investigated drugs to be effective compared with placebo when given as monotherapy except safinamide. When considering combination treatment, the estimated relative effects of selegiline, pramipexole, ropinirole, rotigotine, cabergoline, rasagiline and safinamide were 2.316 (1.819, 2.951), 2.091 (1.889, 2.317), 2.037 (1.804, 2.294), 1.912 (1.716, 2.129), 1.664 (1.113, 2.418), 1.584 (1.379, 1.820) and 1.179 (1.031, 1.352), respectively, compared with joint placebo and levodopa treatment.

CONCLUSIONS

Dopamine agonists were found to be effective as treatment for Parkinson's disease, both when given as monotherapy and in combination with levodopa. Selegiline and rasagiline were also found to be effective for treating Parkinson's disease, and selegiline was the best option in combination with levodopa among all the drugs investigated.

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.

Continuous dopaminergic stimulation (CDS)-based treatment in Parkinson's disease patients with motor complications: a systematic review and meta-analysis

A systematic review of the literature was conducted to identify randomized trials involving continuous dopaminergic stimulation (CDS) in PD patients with motor complications. Difference between n groups was assessed by partitioning heterogeneity and using the χ2 distribution with n-1 degrees of freedom, where n equals the number of groups. We looked for publication bias using funnel plotting, Egger's test and Begg's test. Twenty Randomized Controlled Trials (RCTs) were included. The results showed that CDS could evidently improve the Unified Parkinson's Disease Rating Scale (UPDRS) Part II (p < 0.0001), part III (P < 0.00001) and UPDRS total score (p < 0.00001). There was also a statistical discrepancy in off time reduction (p < 0.00001) and prolongation of on time (p < 0.00001) by the CDS therapy compared with control groups. Meanwhile, the results of this study showed obvious side effects in the CDS therapy compared with the placebo, especially at the expense of increased dyskinesia (23.4% vs 11.7%). The present study showed that CDS was beneficial in the treatment of PD patients with motor complications. But the incidence of the side events is more common than placebo.

Nonergot dopamine-receptor agonists for treating Parkinson's disease - a network meta-analysis

OBJECTIVE

To compare the efficacy of the three nonergot dopamine-receptor agonists (DAs) pramipexole, ropinirole, and rotigotine for the treatment of early and advanced Parkinson's disease (PD).

MATERIALS AND METHODS

Bayesian network meta-analyses were performed separately for early and advanced PD, and at time points 11-16 and 24-28 weeks. Outcomes for early PD included improvement on the Unified Parkinson's Disease Rating Scale (UPDRS) activities in daily life (UPDRS-II), motor function (UPDRS-III), and their subtotal (UPDRS-II + III). Outcomes for advanced PD also included daily "off time" (hours), but not UPDRS-II + III.

RESULTS

Totals of 23 and 24 trials informed early and advanced PD analyses. For early PD UPDRS-II at 11-16 weeks, pramipexole and rotigotine were statistically significantly superior to placebo, but ropinirole was not. For UPDRS-III and UPDRS-II + III, all DAs were statistically significantly better than placebo and exhibited similar improvements. At 24-28 weeks, results were also statistically significant for all DAs versus placebo, and the magnitudes of improvements were similar for pramipexole, ropinirole and rotigotine. Advanced PD improvements on UPDRS-II, UPRDS-III, and off time were statistically significant for pramipexole, ropinirole, and rotigotine versus placebo. At 11-16 weeks, rotigotine yielded slightly smaller effects than ropinirole and pramipexole, but credible intervals on differences were wide. For off time, results were near identical. At 24-28 weeks, results were similar for all three outcomes. Ropinirole yielded a slightly higher improvement on UPDRS-III, but a slightly smaller improvement in off time.

CONCLUSION

Our analyses suggest that pramipexole, ropinirole, and rotigotine exhibit similar efficacy in the treatment of early and advanced PD.

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.

Clinical aspects and management of levodopa-induced dyskinesia

In Parkinson's disease, one of the most troublesome dilemmas is the treatment of levodopa-induced dyskinesia. After a few years, chronic treatment with levodopa is associated with the development of dyskinesias. Strategies to delay or to reduce dyskinesias are based on the change of levodopa dosing or the early use of dopamine agonists. Dopamine agonists with different pharmacological profile are available. Our paper was aimed to analyse the clinical impact and the management of dyskinesias with dopamine agonists.

Dopamine receptor agonists for the treatment of early or advanced Parkinson's disease

Dopamine receptor agonists are indicated for the symptomatic treatment of early, moderate or advanced Parkinson's disease as well as for the reduction of levodopa-related motor complications. Ergolinic dopamine agonists, such as bromocriptine or pergolide, were initially developed and marketed, and then non-ergolinic dopamine agonists, such as pramipexole and ropinirole, were introduced, reducing the risk of drug-induced fibrotic reactions. Once-daily, controlled-release oral and transdermal formulations have been developed aiming at providing more stable 24-hour plasma drug concentrations and more convenient administration. A disease-modifying effect of dopamine agonists has not been demonstrated clinically. As with any other drug, dopamine agonists can also cause adverse drug reactions, which can be related or unrelated to dopaminergic hyperactivation. Dopaminergic reactions include nausea, hallucinations, confusion and orthostatic hypotension, among others, which were readily identified in pre-marketing clinical trials. During post-marketing surveillance, important adverse reactions were identified, such as daytime somnolence, impulse-control disorders and heart valve fibrosis. Other issues, including the efficacy of dopamine agonists for the treatment of non-motor symptoms, remain under evaluation.

Evaluation of the efficacy and safety of adjuvant treatment to levodopa therapy in Parkinson s disease patients with motor complications

BACKGROUND

One of the complications of long-term treatment of Parkinson's disease (PD) with levodopa is the development of motor complications. Generally, when motor complications develop, clinicians add in an additional drug (to the levodopa regimen) from one of three other classes of anti-Parkinsonian treatments (dopamine agonists, catechol-O-methyl transferase inhibitors (COMTIs) or monoamine oxidase type B inhibitors (MAOBIs)). However, despite trials having shown that these drugs are beneficial compared to placebo, it remains unclear as to the best way to treat patients experiencing motor complications and whether one class of drug is more effective than another.

OBJECTIVES

This meta-analysis aims to assess more reliably the benefits and risks of the three classes of drugs (dopamine agonists, COMTIs and MAOBIs) currently used as adjuvant treatment to levodopa in PD patients suffering from motor complications. The three drug classes were compared with the aim of determining whether one class of drug provides better symptomatic control than another.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library), MEDLINE, EMBASE, PubMed, LILACS and Web of Science, plus major journals in the field, abstract books, conference proceedings and reference lists of retrieved publications.

SELECTION CRITERIA

Randomised trials comparing an orally administered dopamine agonist, COMTI or MAOBI versus placebo, both on a background of levodopa therapy, in PD patients experiencing motor complications.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data on off-time, levodopa dose, motor complications, side-effects, treatment concordance, clinician-rated disability, mortality, quality of life and health economic data.

MAIN RESULTS

Forty-four eligible trials, involving 8436 participants were identified. Compared to placebo, adjuvant therapy significantly reduced off-time (-1.05 hours/day, 95% confidence interval (CI) -1.19 to -0.90; P<0.00001), the required levodopa dose (-55.65 mg/day, CI -62.67 to -48.62; P<0.00001) and improved UPDRS scores (UPDRS ADL score: -1.31 points, CI -1.62 to -0.99; P<0.00001; UPDRS motor score: -2.84 points, CI -3.36 to -2.32; P<0.00001; UPDRS total score: -3.26 points, CI -4.52 to -2.00; P<0.00001). However, dyskinesia (odds ratio (OR) 2.50, CI 2.21 to 2.84; P<0.00001) and side-effects including constipation (OR 3.19, CI 2.17 to 4.68; P<0.00001), dizziness (OR 1.57, CI 1.30 to 1.90; P<0.00001), dry mouth (OR 2.33, CI 1.22 to 4.47; P=0.01), hallucinations (OR 2.16, CI 1.70 to 2.74; P<0.00001), hypotension (OR 1.47, CI 1.18 to 1.83; P=0.0007), insomnia (OR 1.38, CI 1.09 to 1.74; P=0.007), nausea (OR 1.78, CI 1.53 to 2.07; P<0.00001), somnolence (OR 1.87, CI 1.40 to 2.51; P<0.0001) and vomiting (OR 2.56, CI 1.67 to 3.93; P<0.0001) were all increased with adjuvant therapy.Indirect comparisons of the three drug classes suggested that dopamine agonists were more efficacious in reducing off-time (dopamine agonist: -1.54 hours/day; COMTI: -0.83 hours/day; MAOBI: -0.93 hours/day; test for heterogeneity between drug classes P=0.0003) and levodopa dose (dopamine agonist: -116 mg/day; COMTI: -52 mg/day; MAOBI: -29 mg/day; test for heterogeneity between drug classes P<0.00001). UPDRS scores also improved more with dopamine agonists than with COMTI or MAOBI (UPDRS total scores - dopamine agonist: -10.01 points versus COMTI: -1.46 points versus MAOBI: -2.20 points; test for heterogeneity between drug classes P<0.00001), although more dyskinesia were seen with dopamine agonists (OR 2.70) and COMTI (OR 2.50) than with MAOBI (OR 0.94) (test for heterogeneity between drug classes P=0.009). Although the increase in the overall incidence of side-effects was generally more marked with dopamine agonists (OR 1.52) and COMTI (OR 2.0) than with MAOBI (OR 1.32), heterogeneity between drug classes was only of borderline significance (P=0.07).

AUTHORS' CONCLUSIONS

Compared to placebo, adjuvant therapy reduces off-time, levodopa dose, and improves UPDRS scores in PD patients who develop motor complications on levodopa therapy. However, this is at the expense of increased dyskinesia and numerous other side-effects. Indirect comparisons suggest that dopamine agonist therapy may be more effective than COMTI and MAOBI therapy, which have comparable efficacy. However, as indirect comparisons should be interpreted with caution, direct head-to-head randomised trials assessing the impact of these different drug classes on overall patient-rated quality of life are needed.

Adding a dopamine agonist to preexisting levodopa therapy vs. levodopa therapy alone in advanced Parkinson's disease: a meta analysis

BACKGROUND

To perform a meta analysis of randomised placebo-controlled trials evaluating the use of dopamine agonist (DA) or placebo to preexisting levodopa therapy for the treatment of advanced Parkinson's disease (PD). We focused on clinically important efficacy [Unified Parkinson's Disease Rating Scale (UPDRS) activities of daily living (ADL) and motor scores as well as change in 'off' time and levodopa dose] and safety outcomes (withdrawal because of adverse drug events (ADEs), dyskinesias, hallucinations and mortality).

METHODS

A systematic literature search was performed between January 1990 and July 2007. The primary outcome measures assessed were the reduction in scores of Unified Parkinson's Disease Rating Scale (UPDRS) activities of daily living (ADL) and motor scores as well as reduction in 'off' time and reductions in levodopa dose from baseline. Safety end-points were also evaluated.

RESULTS

A total of 15 trials (n = 4380 subjects) were included in the meta analysis. Adjunctive DA use resulted in greater improvement as measured by the UPDRS ADL [weighted mean difference (WMD) -2.20, 95% confidence interval (CI) -2.64 to -1.76; p < 0.0001] and motor score reduction (WMD -5.56, 95% CI -6.82 to -4.31; p < 0.0001) as well as reduction in 'off' time measured in hours/day (WMD -1.20, 95% CI -1.78 to -0.62; p < 0.0001) and reduction in levodopa dose (WMD -128.5 mg, 95% CI -175.0 to -82.1; p < 0.0001) vs. placebo. Incidence of dyskinesia and hallucinations was higher with DAs [odds ratio (OR) 3.27, 95% CI 2.65-4.03; p < 0.0001] and (OR 3.34, 95% CI 2.44-4.58; p < 0.0001). Non-ergot DAs were qualitatively better, although both ergot and non-ergot DAs showed statistically significant improvements in all UPDRS scores.

CONCLUSION

Adjunctive DA use to levodopa is superior to levodopa alone in reducing PD symptoms in patients not controlled with monotherapy. DAs seem especially useful amongst PD patients with wearing-off phenomenon from levodopa therapy, but can cause some adverse events.

Deep brain stimulation and continuous dopaminergic stimulation in advanced Parkinson's disease

Patients receiving oral levodopa, the standard treatment for Parkinson's disease (PD), eventually develop motor fluctuations and dyskinesias. Treatment options for patients with these symptoms include high-frequency deep brain stimulation of the subthalamic nucleus (STN-DBS) or continuous dopaminergic stimulation (CDS). STN-DBS is the prevalent surgical therapy for PD and has shown efficacy, but behavioural disorders, including cognitive problems, depression and suicidality have been reported. CDS can be achieved with oral dopamine agonists with a long half-life, transdermal or subcutaneous delivery of dopamine agonists, or intestinal levodopa infusion. Of these, duodenal levodopa infusion appears to be the most promising option in terms of both efficacy and safety.

Efficacy of pramipexole and transdermal rotigotine in advanced Parkinson's disease: a double-blind, double-dummy, randomised controlled trial

BACKGROUND

Continuous dopaminergic drug delivery is an unmet medical need in advanced Parkinson's disease. The aim of this trial-Clinical Efficacy of Pramipexole And Transdermal Rotigotine in Advanced PD (CLEOPATRA-PD)-was to assess the efficacy of adjunct treatment with rotigotine in comparison with placebo and with pramipexole in levodopa-treated patients with advanced Parkinson's disease and wearing-off type motor fluctuations.

METHODS

In this randomised controlled trial, eligible participants were randomly assigned to receive either rotigotine (up to 16 mg/24 h as a transdermal patch), pramipexole (up to 4.5 mg/day orally), or placebo for 6 months. Primary efficacy variables were absolute change in total hours "off" (assessed by home diaries) from baseline to end of study and responder rate (defined as the proportion of patients with >or=30% reduction in absolute off time per day). Analyses were done by intention to treat. This trial is registered with the US National Institutes of Health clinical trials database (ClinicalTrials.gov), number NCT00244387.

FINDINGS

204 patients were randomly assigned to receive rotigotine, 201 to receive pramipexole, and 101 to receive placebo; 427 (84%) completed the trial. The number of discontinuations in each group was similar; most were for adverse events. The mean dose of rotigotine was 12.95 mg/24 h (SD 3.54), the mean dose of pramipexole was 3.1 mg/day (1.24). Mean absolute change in off time from baseline was -2.5 h (SE 0.20) with rotigotine, -2.8 h (0.20) with pramipexole, and -0.9 h (0.29) with placebo. The absolute change in off time from baseline compared with placebo was -1.58 h (95% CI -2.27 to -0.90; p<0.0001) for rotigotine and -1.94 h (-2.63 to -1.25; p<0.0001) for pramipexole. Responder rates were 67% (134 of 200 patients) for pramipexole, 59.7% (120 of 201 patients) for rotigotine, and 35% (35 of 100 patients) for placebo.

INTERPRETATION

In terms of change in absolute off time, rotigotine was non-inferior to pramipexole. Continuous delivery of rotigotine as transdermal patches could offer similar efficacy to oral pramipexole in patients with fluctuating Parkinson's disease over 6 months of treatment.

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.

Review of the therapeutic management of Parkinson's disease. Report of a joint task force of the European Federation of Neurological Societies (EFNS) and the Movement Disorder Society-European Section (MDS-ES). Part II: late (complicated) Parkinson's disease

To provide evidence-based recommendations for the management of late (complicated) Parkinson's disease (PD), based on a review of the literature. Complicated PD refers to patients suffering from the classical motor syndrome of PD along with other motor or non-motor complications, either disease-related (e.g. freezing) or treatment-related (e.g. dyskinesias or hallucinations). MEDLINE, Cochrane Library and INAHTA database literature searches were conducted. National guidelines were requested from all EFNS societies. Non-European guidelines were searched for using MEDLINE. Part II of the guidelines deals with treatment of motor and neuropsychiatric complications and autonomic disturbances. 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.

Qigong exercise for the symptoms of Parkinson's disease: a randomized, controlled pilot study

Irrespective of limited evidence, not only traditional physiotherapy, but also a wide array of complementary methods are applied by patients with Parkinson's disease (PD). We evaluated the immediate and sustained effects of Qigong on motor and nonmotor symptoms of PD, using an add-on design. Fifty-six patients with different levels of disease severity (mean age/standard deviation [SD], 63.8/7.5 years; disease duration 5.8/4.2 years; 43 men [76%]) were recruited from the outpatient movement disorder clinic of the Department of Neurology, University of Bonn. We compared the progression of motor symptoms assessed by Unified Parkinson's Disease Rating Scale motor part (UPDRS-III) in the Qigong treatment group (n = 32) and a control group receiving no additional intervention (n = 24). Qigong exercises were applied as 90-minute weekly group instructions for 2 months, followed by a 2 months pause and a second 2-month treatment period. Assessments were carried out at baseline, 3, 6, and 12 months. More patients improved in the Qigong group than in the control group at 3 and 6 months (P = 0.0080 at 3 months and P = 0.0503 at 6 months; Fisher's exact test). At 12 months, there was a sustained difference between groups only when changes in UPDRS-III were related to baseline. Depression scores decreased in both groups, whereas the incidence of several nonmotor symptoms decreased in the treatment group only.

Salvage of sildenafil failures with cabergoline: a randomized, double-blind, placebo-controlled study

To evaluate the safety and efficacy of cabergoline in men with erectile dysfunction (ED) who did not respond to sildenafil. Four hundred two sildenafil nonresponders aged from 21 to 59 years were included in the study. Patients were randomly divided into group 1, those who received 0.5-1 mg cabergoline weekly for 6 months and group 2, who received placebo for the same period. They underwent preliminary assessment, including medical and sexual history, self-administered International Index of Erectile Function (IIEF) and intravaginal ejaculatory latency time (IVELT) evaluation. Standard biochemistry and hematological laboratory tests, and measurement of serum testosterone and prolactin levels were also carried out. When indicated, other tests were used to establish the diagnosis of vasculogenic and neurogenic ED, including penile color duplex Doppler ultrasonography, pudendal nerve conduction test and impaired sensory-evoked potentials studies. The efficacy of two treatments was assessed every 2 weeks during treatment, at the end of the study, using responses to IIEF, IVELT evaluation, mean intercourse satisfaction domain, mean weekly coitus episodes and adverse drug effects. The trial was completed by 370 (92%) men. Positive clinical results were seen in 31.2% of patients in the cabergoline group compared with 7.1% of patients in the placebo group (P=0.04). The mean weekly intercourse episodes increased from pretreatment values of 1.4 and 1.2 to 2.2 and 1.4, for cabergoline and placebo, respectively (P=0.04). Baseline mean intercourse satisfaction domain values of IIEF 10 and 11 reached to 15 and 10 at 6-month treatment in groups 1 and 2, respectively (P=0.04). The IVELT after cabergoline and placebo gradually increased from 98 and 101 s to approximately 242 and 116 s, respectively (P=0.001). More drug-related adverse effects occurred in cabergoline group and 12 (5.9%) had to discontinue treatment (P=0.001). Cabergoline is moderately effective salvage therapy for sildenafil nonresponse. Further studies with different dosages and treatment regimens are necessary to draw final conclusions on the efficacy of this drug in ED.

Efficacy and safety of high-dose cabergoline in Parkinson's disease

OBJECTIVES

To assess the efficacy and safety of high-dose (up to 20 mg/day) cabergoline in Parkinson's disease (PD) patients with motor fluctuations and/or dyskinesias.

MATERIALS AND METHODS

Thirty-four PD patients had cabergoline up-titrated and their levodopa (L-dopa) reduced over a maximum of 20 weeks, followed by at least 6 weeks steady cabergoline dosing. Primary endpoint was change in mean hyperkinesia intensity at the final visit (week 26).

RESULTS

Mean (+/- SD) cabergoline was increased from 6.43 +/- 2.66 to 12.78 +/- 5.67 mg/day and mean L-dopa reduced from 606.6 +/- 263.9 to 370.6 +/- 192.5 mg/day. A significant reduction (P < 0.001) in mean hyperkinesia intensity occurred from baseline (day 0) to week 26. Improvements in 'on with dyskinesias', mean dystonia intensity (P < 0.05), time spent in 'severe off' condition, severity of 'off' periods as well as clinical/patient global impression, and health-related quality of life were observed. Twenty-four drug-related adverse events were recorded of which four were regarded as serious.

CONCLUSION

High-dose cabergoline was well tolerated and provided significant improvements in the Parkinson symptomatology and a reduced requirement for L-dopa.

Randomized controlled pilot trial of cabergoline, hydergine and levodopa/carbidopa: Los Angeles Cocaine Rapid Efficacy Screening Trial (CREST)

AIM

This study tested three dopaminergic medications against a common unmatched placebo condition: hydergine 1 mg three times daily (n = 15); levodopa/carbidopa 25/100 mg three times daily (n = 15); cabergoline 0.5 mg per week (n = 15); and placebo three times daily (n = 15) as potential pharmacotherapies for cocaine dependence.

DESIGN

The four-parallel group, Cocaine Rapid Efficacy Screening Trial (CREST) design featured a 2-week baseline period followed by randomization to an 8-week medication condition that included 1 hour per week of cognitive behavioral drug counseling. A safety evaluation was conducted 4 weeks after termination.

MEASURES

Outcomes included cocaine metabolites measured in urine, retention and self-reports for drug use, cocaine craving, clinical improvement, mood and HIV risk behaviors.

RESULTS

Participants assigned to receive cabergoline provided more urine samples negative for cocaine metabolites (42.4%) than those assigned to receive placebo (25.0%), a statistically significant difference after controlling for baseline differences in self-reported cocaine use (F = 2.95, df = 3; P = 0.05). Cabergoline-treated participants demonstrated a significant improvement over placebo from baseline to week 8 when measured using the Addiction Severity Index (ASI) employment subscale (overall change = - 0.09, SD = 0.10, t = 2.36, P < 0.05). Safety and adverse event measures showed similar rates and types of complaints by treatment condition.

CONCLUSIONS

These results, combined with the apparent safety of cabergoline when used with this population, provide empirical support for conducting a larger study of the medication.

Cabergoline

Cabergoline is a synthetic ergoline dopamine agonist with a high affinity for dopamine D2 receptors and a long elimination half-life. This agent provides continuous dopaminergic stimulation with once-daily administration. Adjuvant oral cabergoline is usually well tolerated and effective in controlling symptoms in patients with advanced Parkinson's disease experiencing response fluctuations to long-term levodopa therapy. In patients with early Parkinson's disease, cabergoline (with or without levodopa) is well tolerated and effective in controlling disease symptoms, and may reduce the risk of developing drug-induced motor complications. Data from two pharmacoeconomic analyses suggest that cabergoline may be a cost-effective treatment option versus levodopa in patients with early Parkinson's disease, and highlight the need for further evaluation of the drug in this indication.

Clinical pharmacokinetics of cabergoline

Cabergoline is a synthetic ergoline dopamine agonist with a high affinity for D(2) receptors indicated for use in both early and advanced Parkinson's disease and in hyperprolactinaemic disorders. Following oral administration, peak plasma concentrations of cabergoline are reached within 2-3 hours. Over the 0.5-7mg dose range, cabergoline shows linear pharmacokinetics in healthy adult volunteers and parkinsonian patients. Cabergoline is moderately bound (around 40%) to human plasma proteins in a concentration-independent manner; concomitant administration of highly protein-bound drugs is unlikely to affect its disposition. The absolute bioavailability of cabergoline is unknown. Cabergoline is extensively metabolised by the liver, predominantly via hydrolysis of the acylurea bond of the urea moiety. Cytochrome P450-mediated metabolism appears to be minimal. The major metabolites identified thus far do not contribute to the therapeutic effect of cabergoline. A significant fraction of the administered dose undergoes a first-pass effect. Less than 4% is excreted unchanged in the urine. The elimination half-life of cabergoline estimated from urinary data of healthy subjects ranges between 63 and 109 hours. Mild to moderate renal and hepatic impairment, administration of food and the use of concomitant antiparkinsonian medications, such as levodopa and selegiline, have no effect on the pharmacokinetics of cabergoline.The pharmacokinetic properties of cabergoline allow once daily administration in patients with Parkinson's disease and twice weekly administration in patients with hyperprolactinaemia, making this drug advantageous over other dopaminergic agents in term of both therapeutic compliance and better symptom control.

Comparing dopamine agonists in Parkinsonʼs disease

Dopamine agonists are effective in the management of both advanced and early-stage Parkinson's disease. Unfortunately, randomized head-to-head comparative studies between the many different dopamine agonists now available are sparse. Indirect comparisons of dopamine agonists show that ergot derivatives, such as pergolide and cabergoline, are as effective as non-ergot derivatives, such as ropinirole and pramipexole, in ameliorating Parkinson's disease symptoms in patients in early or advanced stages of the condition. As far as safety and tolerability are concerned, no significant differences between dopamine agonists are found. However, some specific adverse events, such as somnolence and sleep attacks, seem less frequent in monotherapy studies with pergolide than in those with the non-ergot dopamine agonists; however, because of the lack of direct-comparison studies this cannot be proved conclusively. Randomized, controlled comparative studies between dopamine agonists are necessary to verify any possible differences in their effectiveness and tolerability in the treatment of Parkinson's disease.

Chronic treatment with small doses of cabergoline prevents dopa-induced dyskinesias in parkinsonian monkeys

Levodopa continues to be the most effective agent for the symptomatic treatment of Parkinson's disease (PD). But over time, initial benefits decline in efficacy because of a rise in adverse effects such as dyskinesias. The pathophysiology of levodopa-induced dyskinesias (LID) is not completely understood, but it appears to result from deficient regulation by dopamine of corticostriatal glutamatergic inputs leading to a cascade of neurochemical changes in the striatum and the output pathways. In the present study, we examined if the addition of small doses of cabergoline (a long-acting D(2) receptor agonist) to levodopa could prevent LID. The major hypothesis is that sustained activation of postsynaptic D(2) receptors on medium spiny neurons even by small doses of cabergoline could prevent or reduce LID. The minor hypothesis, and the more controversial of the two, is that the long-acting stimulation by small doses of cabergoline could diminish the release of glutamate by the corticostriatal pathway and prevent LID. Eight MPTP-treated monkeys with a long-standing and stable parkinsonian syndrome and having never received dopaminergic agents were used. Two groups of four were treated for 1 month with levodopa/benserazide administered orally (100 mg/25 mg). The second group received in addition a threshold dose of cabergoline (dose ranging from 0.015 to 0.035 mg/kg, SC). During the treatment, we observed LID in the levodopa group but not in the group receiving levodopa+cabergoline. Furthermore, the combination produced a comparable antiparkinsonian effect in terms of quality but prolonged the duration (by 1 to 2 hours) and increased the locomotion (mean for 2 weeks congruent with 104%). Our data suggest that a small dose of a long-acting D(2) agonist combined with high doses of levodopa could be preventive of LID in patients with PD and could be an alternative to using antiglutamatergic agents for this purpose.

Potential of transdermal drug delivery in Parkinson's disease

There has been a growing recognition that pulsatile stimulation of dopamine receptors may be an important mechanism in the generation of the motor fluctuations that often develop and compromise the effectiveness of long-term levodopa administration in persons with Parkinson's disease (PD). This has prompted investigation of treatment approaches that might provide more constant, and therefore physiological, dopamine receptor stimulation. Frequent levodopa administration, controlled-release levodopa preparations, inhibitors of levodopa metabolism, and duodenal, subcutaneous and even intravenous infusions of levodopa or dopamine agonists have all been employed with this goal in mind, but all have limitations. Transdermal drug delivery is a treatment approach that is not only capable of providing a constant rate of drug delivery, but is also non-invasive and relatively simple to use. However, developing a drug to be delivered transdermally for the treatment of PD has been anything but easy. Levodopa and many dopamine agonists are not sufficiently soluble to be administered via the transdermal route, and blind alleys have been encountered thus far in the investigation of suitably soluble drugs. Nevertheless, investigation continues and yet another candidate drug, rotigotine (N-0923), is currently under active investigation. Techniques designed to enhance skin permeation and thus improve the effectiveness of transdermal drug delivery are also potential sources for future treatment advances.

Use of the dopamine agonist cabergoline in the treatment of movement disorders

Cabergoline is an ergot-derived dopamine agonist used in the treatment of Parkinson's disease (PD). Both ergot and non-ergot-derived dopamine agonists directly stimulate dopamine receptors, unlike levodopa, which must undergo presynaptic breakdown to dopamine beforehand. Cabergoline has the longest half-life of the dopamine agonists currently available and is effective when given once-daily. It has been proposed that therapy with cabergoline may mimic physiological dopaminergic stimulation in PD by providing striatal intrasynaptic dopamine replacement. Its long half-life is likely to result in sustained rather than pulsatile dopaminergic stimulation, the preferred manner of treating PD. Placebo-controlled trials using cabergoline as an adjunctive therapy in PD have shown that it significantly reduces 'off' time, improves motor function and reduces levodopa requirements. Cabergoline has been shown to be as effective as other dopamine agonists in improving motor function as monotherapy in early PD, and a 5-year levodopa-controlled study indicates the superiority of cabergoline over levodopa in reducing dyskinesias. The efficacy of cabergoline in PD patients with nocturnal disabilities, restless leg syndrome and augmentation has also been demonstrated. Audits of the clinical efficacy of cabergoline indicate that it is well-tolerated and has an acceptable side effect profile.

The novel use of very high doses of cabergoline and a combination of testosterone and an aromatase inhibitor in the treatment of a giant prolactinoma

Most prolactinomas respond rapidly to low doses of dopamine agonists. Occasionally, stepwise increases in doses of these agents are needed to achieve gradual prolactin (PRL) reductions. Approximately 50% of treated men remain hypogonadal, yet testosterone replacement may stimulate hyperprolactinemia. A 34-yr-old male with a pituitary macroadenoma was found to have a PRL level of 10,362 micro g/liter and testosterone level of 3.5 nmol/liter. Eleven months of dopamine agonist therapy at standard doses lowered PRL levels to 299 micro g/liter. Subsequent stepwise increases in cabergoline (3 mg daily) further lowered PRL levels to 71 micro g/liter, but hypogonadism persisted. Initiation of testosterone replacement resulted in a rise and discontinuation in a fall of PRL levels. Aromatization of exogenous testosterone to estradiol and subsequent estrogen-stimulated PRL release was suspected. Concomitant use of cabergoline with the aromatase inhibitor anastrozole after resuming testosterone replacement resulted in the maintenance of testosterone levels and restoration of normal sexual function, without increasing PRL. Ultimately, further reduction in PRL on this therapy permitted endogenous testosterone production. Thus, novel pharmacological maneuvers may permit successful medical treatment of some patients with invasive macroprolactinomas.

Clinical pharmacokinetic and pharmacodynamic properties of drugs used in the treatment of Parkinson's disease

Current research in Parkinson's disease (PD) focuses on symptomatic therapy and neuroprotective interventions. Drugs that have been used for symptomatic therapy are levodopa, usually combined with a peripheral decarboxylase inhibitor, synthetic dopamine receptor agonists, centrally-acting antimuscarinic drugs, amantadine, monoamine oxidase-B (MAO-B) inhibitors and catechol-O-methyltransferase (COMT) inhibitors. Drugs for which there is at least some evidence for neuroprotective effect are certain dopamine agonists, amantadine and MAO-B inhibitors (selegiline). Levodopa remains the most effective drug for the treatment of PD. Several factors contribute to the complex clinical pharmacokinetics of levodopa: erratic absorption, short half-life, peripheral O-methylation and facilitated transport across the blood-brain barrier. In patients with response fluctuations to levodopa, the concentration-effect curve becomes steeper and shifts to the right compared with patients with stable response. Pharmacokinetic-pharmacodynamic modelling can affect decisions regarding therapeutic strategies. The dopamine agonists include ergot derivatives (bromocriptine, pergolide, lisuride and cabergoline), non-ergoline derivatives (pramipexole, ropinirole and piribedil) and apomorphine. Most dopamine agonists have their specific pharmacological profile. They are used in monotherapy and as an adjunct to levodopa in early and advanced PD. Few pharmacokinetic and pharmacodynamic data are available regarding centrally acting antimuscarinic drugs. They are characterised by rapid absorption after oral intake, large volume of distribution and low clearance relative to hepatic blood flow, with extensive metabolism. The mechanism of action of amantadine remains elusive. It is well absorbed and widely distributed. Since elimination is primarily by renal clearance, accumulation of the drug can occur in patients with renal dysfunction and dosage reduction must be envisaged. The COMT inhibitors entacapone and tolcapone dose-dependently inhibit the formation of the major metabolite of levodopa, 3-O-methyldopa, and improve the bioavailability and reduce the clearance of levodopa without significantly affecting its absorption. They are useful adjuncts to levodopa in patients with end-of-dose fluctuations. The MAO-B inhibitor selegiline may have a dual effect: reducing the catabolism of dopamine and limiting the formation of neurotoxic free radicals. The pharmacokinetics of selegiline are highly variable; it has low bioavailability and large volume of distribution. The oral clearance is many-fold higher than the hepatic blood flow and the drug is extensively metabolised into several metabolites, some of them being active. Despite the introduction of several new drugs to the antiparkinsonian armamentarium, no single best treatment exists for an individual patient with PD. Particularly in the advanced stage of the disease, treatment should be individually tailored.

Treatment interventions for Parkinson's disease: an evidence based assessment

We did a systematic review, with a uniform method of assessment of efficacy and safety, to assess the different interventions available for the management of Parkinson's disease (drugs, surgical interventions, and physical treatments) with respect to the following indications: prevention of disease progression, symptomatic treatment of motor features (parkinsonism), symptomatic control of motor complications, prevention of motor complications, and symptomatic treatment of non-motor features. Our aim was not to define practice guidelines, but rather to improve clinicians' knowledge of the presently available published clinical evidence, based mainly on randomised controlled trials. We hope that our review will help doctors to incorporate this background into their own decision-making strategy to make appropriate choices with respect to the treatment of individual patients with Parkinson's disease.

The use of pramipexole in Parkinson's disease: are its actions D(3) mediated?

Pramipexole is a non-ergot dopamine agonist recently approved for the treatment of early and advanced Parkinson's disease (PD). It has preferential affinity for the D(3) dopamine receptor, compared to previous dopamine agonists that have higher affinity for D(2) dopamine receptors. The ultimate question is whether its efficacy is linked to its action at the D(3) dopamine site or due to its binding to D(2) dopamine receptors. There is no direct experimental evidence available to answer this question. Based on a review of the pharmacological literature, it is likely that the motor benefits of pramipexole in PD patients are due to D(2) stimulation, whereas its putative effects on mood and apathy may be related to its D(3) agonist properties.

Cabergoline for levodopa-induced complications in Parkinson's disease

BACKGROUND

Long term levodopa therapy in Parkinson's disease is associated with the development of motor complications including abnormal involuntary movements and a shortening response to each dose (wearing off phenomenon). It is thought that dopamine agonists can reduce the duration of immobile off periods and the need for levodopa therapy whilst maintaining or improving motor impairments and only minimally increasing dopaminergic adverse events.

OBJECTIVES

To compare the efficacy and safety of adjuvant cabergoline therapy versus placebo in patients with Parkinson's disease, already established on levodopa and suffering from motor complications.

SEARCH STRATEGY

Electronic searches of MEDLINE, EMBASE and the Cochrane Controlled Trials Register. Handsearching of the neurology literature as part of the Cochrane Movement Disorders Group's strategy. Examination of the reference lists of identified studies and other reviews. Contact with Pharmacia Upjohn Limited.

SELECTION CRITERIA

Randomised controlled trials of cabergoline versus placebo in patients with a clinical diagnosis of idiopathic Parkinson's disease and long-term complications of levodopa therapy.

DATA COLLECTION AND ANALYSIS

Data was abstracted independently by the authors and differences settled by discussion. The outcome measures used included Parkinson's disease rating scales, levodopa dosage, off time measurements and the frequency of withdrawals and adverse events.

MAIN RESULTS

Cabergoline has been compared with placebo in two phase II (6 - 12 weeks) and one phase III randomised controlled trials (24 weeks). These were double-blind, parallel group, multicentre studies including 268 patients with Parkinson's disease and motor complications. The reduction of 1.14 hours (WMD; 95% CI -0.06, 2.33; p = 0.06) in off time in favour of cabergoline was not statistically significant. Inadequate data on dyskinesia was collected either on rating scales or as adverse event reporting to allow a conclusion to be drawn. A small but statistically significant advantage of cabergoline over placebo was seen in one study for UPDRS ADL (part II) score and UPDRS motor score. No such advantage was seen in one other study due to small numbers of patients and the comparatively low doses of cabergoline used. No significant differences in Schwab and England scale were seen in two studies. Levodopa dose reduction was significantly greater with cabergoline (WMD 149.6 mg/d; 95% CI 94.1, 205.1; p < 0.00001). There was a trend towards more dopaminergic adverse events with cabergoline but this did not reach statistical significance at the p < 0.01 level. However, there was a trend towards fewer withdrawals from cabergoline.

REVIEWER'S CONCLUSIONS

In the management of the motor complications seen in Parkinson's disease, cabergoline can be used to reduce levodopa dose and modestly improve motor impairment and disability with an acceptable adverse event profile. These conclusions are based on, at best, medium term evidence.

Dopamine agonists: the treatment for Parkinson's disease in the XXI century?

Levodopa combined with a peripheral dopa-decarboxylase inhibitor (DCI) has been considered the therapy of choice for Parkinson's disease (PD). Levodopa is nearly always effective, but has a high incidence of adverse effects with long term use, including response fluctuations (on/off phenomena) and dyskinesias. Dopaminergic agonists, acting directly at the receptor level, would be able to decrease the incidence of these motor complications.In progressive neurodegenerative diseases, such as PD, modification of the rate of disease progression (often referred to as neuroprotection) is currently a highly debated topic. Increased oxidative stress is thought to be involved in nigral cell death, that is characteristic of PD. This oxidative stress may be further exacerbated by levodopa therapy. These mechanisms have been proven in vitro and animal models, but it's relevance in humans remains speculative.Based on the considerations above, the emerging therapeutic strategies for PD advocate early use of dopamine agonists in the treatment of PD. A number of recent well-controlled studies have proven the efficacy of dopamine agonists used as monotherapy. Moreover, as predicted by animal studies, on the long term, dopaminergic agonists induce significantly less motor complications than levodopa.In the last 2years, three new dopamine agonists have been launched, including ropinirole, pramipexole and cabergoline. These new agonists have been added, as therapeutical options to well-established drugs, like pergolide, bromocriptine or talipexole. The recently launched compounds have proven efficacy in monotherapy and as adjunctive therapy to levodopa. Unfortunately, only a very limited amount of comparative data among the different agonists is available. Pergolide has proven to be a superior drug to bromocriptine as adjunctive therapy to levodopa in a significant number of studies and is considered the gold standard dopamine agonist. Nevertheless, none of the recently launched compounds has compared itself against pergolide.A comparison of monotherapy trials is difficult, because of differences in design and populations. In a recently completed trial pergolide was statistically significantly better than placebo in all the efficacy parameters tested, with 57% of pergolide treated patients improving over 30% in the motor section of the UPDRS, as compared to 17% in the placebo arm. Interestingly, these results were obtained in the absence of any other antiparkinsonian drug during the trial. Recent monotherapy trials done with ropinirole and pramipexole achieved also significant improvements as monotherapy, but in these cases selegeline, a drug that causes a symptomatic improvement in PD, was allowed as co-medications during the trial. Not all trials used the same efficacy measures, i.e. monotherapy trials with pergolide and ropinirole used a "responder" based analysis (responder were all patients that improved 30% or more on the motor section of UPDRS), as well as a baseline to endpoint improvement in motor scores. Pramipexole monotherapy trials used only the latter approach, which is clinically less powerful than a responder analysis.Even with the difficulties mentioned above, all the recent trials with dopamine agonists have proven that these drugs are a useful symptomatic long term treatment for PD with or without levodopa and that the early use of dopamine agonists reduces the incidence of motor complications as compared to levodopa.

A comparison of dopamine agonists and catechol-O-methyltransferase inhibitors in Parkinson's disease

To compare the efficacy and tolerability of three dopamine agonists--pergolide (PRG), pramipexole (PRX), and ropinirole (ROP)-and two catechol-O-methyltranferase (COMT) inhibitors-tolcapone (TOL) and entacapone (ENT)-as add-on therapies to levodopa (L-Dopa) in Parkinson's disease, we analyzed randomized, double-blind, placebo-controlled, multicenter studies. To our knowledge, they had not yet been evaluated in comparison with each other. Statistical analyses used odds ratios, numbers needed to harm, and Fisher's inverse chi2 method. Seven studies meeting the inclusion criteria included treatment of 1,756 patients. The common efficacy measures were the reduction of L-Dopa dose and "off' duration. The reported reduction in L-Dopa dose was significant for all drugs in relation to placebo, but was most significant for PRX and ENT (p < 0.0001). The most significant reduction in "off' duration was with PRG, PRX, and ENT (p < 0.001). The common tolerability measures were the percentage of patients withdrawn because of side effects, because of any reason, and because of the development of dyskinesias. Ropinirole, PRX, and ENT caused fewer withdrawals related to side effects. Pergolide was better than other analyzed drugs concerning withdrawals for any reason. All drugs caused more dyskinesias than placebo (p < 0.0001), with overlapping confidence intervals, except for TOL 600 mg, which caused more dyskinesias than dopamine agonists and ENT. Pramipexole and ENT had the best efficacy and tolerability profile in this analysis.

Sustained cabergoline treatment reverses levodopa-induced dyskinesias in parkinsonian monkeys

The pathophysiology of L-Dopa-induced dyskinesias (LID), a common problem after long-term use of L-dopa in the treatment of Parkinson's disease (PD), is not completely understood. Oscillations in L-Dopa concentrations in the brain are believed to be responsible, at least in part, for their pathogenesis. This study was aimed at verifying whether chronic administration of cabergoline, a long-acting dopamine D2-like receptor agonist, can reverse established LID. Four MPTP-treated cynomolgus monkeys with long-standing and stable parkinsonian syndrome and reproducible dyskinesias to L-Dopa, were used in this study. We compared the antiparkinsonian and dyskinetic responses of L-Dopa methyl ester (62.5 mg and 125 mg), given with benserazide (50 mg) (L-Dopa/benserazide), administered before and after a 6-week period during which the animals were treated only by daily administration of cabergoline (doses ranging from 0.125 to 0.185 mg/kg, subcutaneous). During cabergoline treatment, the monkeys initially showed marked dyskinesias, which were reduced significantly after 4 weeks of treatment. However, there was no tolerance to its antiparkinsonian effect. L-Dopa/benserazide given 4 days after cabergoline withdrawal produced a significant antiparkinsonian effect, but dyskinesias were dramatically reduced compared to what had been seen before chronic cabergoline treatment. The duration of the L-Dopa response was not increased after chronic administration of cabergoline. Our data suggest that sustained dopamine D2 receptor stimulation could be of value when trying to reduce or to reverse LID in patients with fluctuating advanced PD.

Clinical pharmacology of dopamine agonists

With the availability of newer dopamine agonists selective for dopamine (D2) receptor subtypes, medical management of Parkinson's disease has progressed substantially. These agents can decrease the frequency of ergot-related side effects and dyskinesias. Also, when given as adjunctive therapy with levodopa, they can allow the levodopa maintenance dosage to be reduced without loss of symptom control. Based on early clinical experience, dopamine agonists can also be prescribed as initial monotherapy and can delay therapy with levodopa. Their therapeutic roles will be defined further by long-term studies.

New drugs for the treatment of Parkinson's disease

Since the introduction of levodopa to treat Parkinson's disease (PD), several new therapies have been directed at improving symptom control, which can decline after a few years of levodopa therapy. Dopaminergic agents can serve as adjuncts or as alternatives to levodopa. In addition, a new class of drugs, catechol-O-methyltransferase inhibitors, can extend the duration of levodopa action. Although surgical options such as pallidotomy offer improvement of parkinsonism beyond the realm of pharmacologic treatment, judicious administration of drugs in combination can generally solve most problems of PD.

Dopamine agonists: what is the place of the newer compounds in the treatment of Parkinson's disease?

Three new dopamine agonists (cabergoline, pramipexole, ropinirole) have been put on to the market within the past months to treat patients with Parkinson's disease. Like any marketed dopamine agonists, the new compounds bind to the D2-like receptors. Pramipexole and ropinirole appear to be quite close drugs. Both are selective non ergot D2 (and preferentially D3) agonists, with an elimination half-life of 5 to 10 hours. Conversely, cabergoline is an ergot derivative, less selective for the D2 receptors, with a much longer elimination half-life (60 hours or more). In moderately advanced levodopa treated patients with Parkinson's disease and motor fluctuations, cabergoline, pramipexole and ropinirole all do significantly better than placebo in reducing UPDRS motor examination scores, time spent off and daily dose of levodopa. None of the 3 newer agonists proved to do significantly better than bromocriptine in this indication, at the cost of very similar adverse effects. In de novo levodopa naive patients, pramipexole and ropinirole did significantly better than placebo in short-term (few months) follow-up trials, at the cost again of classical dopaminergic adverse effects. Ropinirole was marginally more effective than bromocriptine, while its use induced the same risk of psychosis than the "old" reference agonist. Early treatment with cabergoline, compared with levodopa, in a long-term (5 year) study reduced the relative risk of developping motor complication by more than 50%. A similar study is presently on-going to compare ropinirole and levodopa. Clinical trials to assess putative neuroprotective effects are also on going with ropinirole and pramipexole. Up to now, the available clinical controlled data suggest that the newer dopamine agonists have very similar clinical effects with only minor superiority, if any, versus bromocriptine.

A review of health-related quality-of-life concepts and measures for Parkinson's disease

Parkinson's disease affects individuals health-related quality of life (HQL). Including standardized HQL assessments in therapeutic clinical trials will broaden our understanding of treatment efficacy. Selecting appropriate HQL measures for clinical studies requires consideration of their comprehensiveness, psychometric properties and feasibility. To facilitate selection, this manuscript reviews the HQL areas affected by Parkinson's disease and available Parkinson's disease-specific HQL measures: the Parkinson's Disease Questionnaire--39 (PDQ-39) and the Parkinson's Disease Quality-of-Life Questionnaire (PDQL). Based on a literature review and consultation with HQL experts, five clinicians and three patients, 12 areas of HQL were identified as particularly relevant to Parkinson's disease: physical function, mental health/emotional well being, self-image, social function, health-related distress, cognitive function, communication, sleep and rest, eating, role function, energy/fatigue, and sexual function. The PDQ-39 measures all areas except for self-image and sexual function. The PDQL measures all areas except for eating and role function. Both measures are brief and are designed and validated to be self-completed by patients. Both measures demonstrate adequate internal consistency (PDQ-39: 0.72-0.95; PDQL: 0.80-0.87) and evidence of cross-sectional validity with patient-reported measures of similar concepts. The PDQ-39 also demonstrates reproducibility (0.68-0.94), significant associations with clinical measures and preliminary evidence of responsiveness. Applications of the PDQ-39 and PDQL to clinical trials will contribute greatly towards their continued validation and interpretation.

Parkinson's Disease: The Proper Use of Dopamine Receptor Agonists

Although dopamine receptor agonists are not simple to use, they are assuming increased importance in the treatment of early and advanced symptoms of Parkinson's disease (PD). The new agonists, pramipexole and ropinirole, are generally adequate without levodopa for early symptoms and carry the hope for a more acceptable profile of long-term side effects. In the patient with advanced disease, all four dopamine agonists significantly augment the response to levodopa, which reduces the problems of motor fluctuations and drug-related dyskinesia. Understanding the common pitfalls when prescribing these drugs will facilitate their safety and efficacy.

Dopamine agonists

Dopamine agonists have been used in the treatment of Parkinson's disease (PD) since the mid 1970s. With the approval of two new agents in 1997, the number available in the United States is up to four; bromocriptine, pergolide, pramipexole, ropinirole. These agents differ in dopamine receptor affinities and chemical structure, which, in turn, may possibly result in differences in efficacy tolerability and safety. Dopamine have historically been used in combination with levodopa in patients with advanced PD, but indicators are now expanding. With is expansion comes increasing controversy. This article reviews dopamine receptor pharmacology and the results of the clinical trials that have used for agonists available in the United States as well as a discussion of three minor agonists.

Motor fluctuations in Parkinson's disease: pathophysiology and treatment

At the initial stages of Parkinson's disease (PD), levodopa (LD) is able to reduce most motor symptoms and to significantly improve the patient's quality of life. However, in the vast majority of patients with prolonged LD usage, some decline in efficacy occurs and motor complications eventually begin to appear. These complications consist not only of daily fluctuations in the voluntary motor performance often accompanied by involuntary movements, but also of fluctuations in cognitive, autonomic, and sensory functions. Several recent studies on LD complications in PD have led to a better understanding of their pathophysiology and of the possible therapeutic interventions, and a summary of these findings is presented in this review. Different observations now suggest that postsynaptic pharmacodynamic factors play a major role in determining fluctuations in PD. Two explanations are given: chronic intermittent dopaminergic therapy may lead to postsynaptic receptor downregulation in PD; or, receptor changes in the striatum may occur independently of treatment as a result of structural adaptation of the postsynaptic dopaminergic system to the progressive decline of the nigrostriatal pathway. The hypothesis of reversible postsynaptic changes as the main mechanism underlying a fluctuating response to LD lends itself to a possible pharmacological manipulation of the dopaminergic response to reverse, or even avoid, motor fluctuations (initial monotherapy with dopamine agonists and early combination LD/dopamine agonists). The role of peripheral pharmacokinetics factors is also critical and the use of controlled release LD formulations, of monoamine oxidase (MAO)-B and of catechol-O-methyltransferase (COMT) inhibitors may all, to a different degree, improve such phenomena. In the last decade, there has been a resurgence in surgical therapies in advanced PD, due to higher levels of accuracy and safety provided by the new surgical devices, and to a more precise localization of the target areas allowed by the neurophysiological mapping techniques. The surgical procedures currently used in advanced PD are stereotactic brain lesions (internal globus pallidus and subthalamic nucleus), chronic brain stimulation (of the same nuclei) and striatal grafting of dopamine-producing cells. All these procedures have already shown their efficacy in the management of severe fluctuations in PD, but their indications, and relative advantages and disadvantages, are still the subject of considerable debate and controversy.

Clinical pharmacology of dopamine agonists in Parkinson's disease

Oral levodopa is the most effective symptomatic treatment for Parkinson's disease. Dopamine agonists are useful adjuvants to levodopa in the pharmacotherapy of parkinsonian patients. Monotherapy with dopamine agonists in early Parkinson's disease has been advocated in order to delay the occurrence of complications associated with long term administration of levodopa. The use of dopamine agonists alone provides an adequate antiparkinsonian effect in only a minority of patients. In early stages of Parkinson's disease, dopamine agonists can produce a clinical response comparable with levodopa but, thereafter, their efficacy wanes. Early initiation of combination therapy with levodopa and dopamine agonists appears to reduce the severity and delay the appearance of the complications associated with long term administration of levodopa. Currently, dopamine agonists are most commonly used in combination with levodopa in patients in advanced stages of the disease who experience fluctuations of their motor symptoms. Despite their different pharmacodynamic and pharmacokinetic profiles, the ergot derivatives bromocriptine, lisuride and pergolide appear to be very similar in terms of their clinical efficacy. Continuous dopaminergic stimulation by parenteral infusion of water-soluble dopamine agonists such as apomorphine and lisuride can overcome motor fluctuations in advanced Parkinson's disease. Other dopamine agonists such as cabergoline, pramipexole and ropinirole are currently being studied. Further studies with these compounds will be required to determine their efficacy and adverse effects in comparison with the currently available orally active ergot agonists. It has been suggested that oxidative stress resulting from dopamine metabolism may be reduced by the administration of dopamine agonists. These drugs may therefore slow the rate of progression of Parkinson's disease. At present, however, there is no convincing clinical data to support a neuroprotective effect of dopamine agonists.

Clinical experience with cabergoline in patients with advanced Parkinson's disease treated with levodopa

The clinical efficacy of the long-acting dopamine agonist cabergoline as an adjunct to levodopa has been investigated in controlled and uncontrolled studies in > 1500 patients with advanced Parkinson's disease and motor complications. Four of these studies (including 2 comparisons with placebo and 2 with bromocriptine), which used similar methodology (including study design, blindness, selection criteria, treatment modalities and duration) and measurements of efficacy and safety, are reviewed. Compared with placebo, cabergoline 2 to 10 mg/day (median 5 mg/day) induced a significantly higher percentage decrease in the number of 'off' hours (18 vs 45%) in a preliminary phase II study that included 37 patients with severe motor fluctuations. This was not associated with an increase in dyskinesia in either treatment group. In a subsequent phase III placebo-controlled study (n = 188 patients with motor fluctuations), treatment with cabergoline 0.5 to 5 mg/day (median 3.5 mg/day) achieved a statistically significant decrease in levodopa dosage compared with placebo (18 vs 3%) and improved the Unified Parkinson's Disease Rating Scale scores for activities of daily living in a greater number of patients (23 vs 4%). Comparisons of cabergoline with bromocriptine have been conducted in 750 patients stabilised on levodopa therapy; one study was conducted in patients without, and the other in patients with, previous exposure to dopamine agonists. Cabergoline was administered once daily at doses ranging from 0.5 to 6 mg, and bromocriptine was given at a dosage of 5 to 40 mg/day divided into 3 administrations. A combined analysis of the response rates obtained in the 2 studies found cabergoline to be at least as effective and well tolerated as bromocriptine, with a trend in favour of cabergoline in terms of response rate and number of 'off' hours. The majority of adverse events in this patient population were those associated with levodopa therapy, as shown by the high frequency of adverse events in the placebo group (68%). Both cabergoline and bromocriptine showed a comparable incidence of adverse events, with CNS and gastrointestinal events being the most common. Thus, the potential advantages of cabergoline include improved patient compliance as a result of its once-daily administration, and an increased threshold for the development of dyskinesia as a result of the levodopa sparing effect of cabergoline.

Effects of acute or prolonged administration of cabergoline on parkinsonism induced by MPTP in common marmosets

The effects of a single treatment or chronic administration of cabergoline (1-[(6-allylergolin-8beta-yl)carbonyl]-1-[3-(dimethylamino)p ropyl]-3-ethyl-urea), a potent, long-lasting dopamine receptor agonist, on parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in common marmosets were studied. The administration of 0.2 mg/kg or a higer dose of cabergoline began to reverse parkinsonism-like symptoms 60 min after a subcutaneous injection, and showed steady and constant effects throughout the observation period. For prolonged administration, 0.2 mg/kg cabergoline was injected daily for 22 consecutive days. Locomotor activity in MPTP-treated animals increased until it reached its peak on the third day, then it gradually decreased. Akinesia scores, rating the quality of movements, were also improved, and the improvement was sustained up to the last day of chronic administration. None of the animals developed abnormal behaviors after either acute or chronic administration. These results suggest that cabergoline has long-acting effects in the marmoset model of parkinsonism, and that it will be a useful agent for the treatment of Parkinson's disease, particularly in cases with fluctuating motor disabilities.

Entacapone improves motor fluctuations in levodopa-treated Parkinson's disease patients. Parkinson Study Group

Motor fluctuations associated with levodopa therapy are common problems encountered in the long-term treatment of Parkinson's disease (PD). Entacapone, a peripherally acting, reversible inhibitor of catechol-O-methyltransferase, slows the elimination of levodopa in humans by reducing the formation of 3-O-methyldopa. We conducted a placebo-controlled, double-blind, parallel-group, multicenter trial of entacapone in PD patients with motor fluctuations. Two hundred five patients were randomized to receive either entacapone 200 mg or matching placebo with each dose of levodopa and were followed for 24 weeks. The primary measure of efficacy was the change in percentage of "on" time (relief of parkinsonism) while awake, as recorded by subjects at home in diaries completed at 30-minute intervals. At baseline, patients averaged approximately 10 hours of "on" time per day while awake (60.5% "on" time), and entacapone treatment increased the percent "on" time by 5.0 percentage points. The effect of entacapone was more prominent in patients with a smaller percent "on" time (<55%) at baseline, and increased as the day wore on. Entacapone is effective at increasing the duration of response to levodopa and at relieving parkinsonism in patients experiencing motor fluctuations and was well tolerated during the 24 weeks of treatment.

New pharmacotherapy for Parkinson's disease

OBJECTIVE

To summarize the development, pharmacology, pharmacokinetics, efficacy, and safety of five investigational antiparkinsonian drugs that are in or have recently completed Phase III trials: three dopamine agonists, pramipexole, ropinirole, and cabergoline; and two catechol-O-methyltransferase (COMT) inhibitors, entacapone and tolcapone. The pathophysiology and the role of dopamine in Parkinson's disease are also reviewed.

DATA SOURCES

A MEDLINE search of relevant English-language literature, clinical studies, abstracts, and review articles pertaining to Parkinson's disease was conducted. Manual searches of 1996/1997 meeting abstracts published by the American Academy of Neurology and the Movement Disorders Society were also performed. Manufacturers provided unpublished Phase III trial efficacy and pharmacokinetic data.

STUDY SELECTION AND DATA EXTRACTION

Clinical trial investigations selected for inclusion were limited to human subjects. Interim analyses after 6 months for long-term clinical studies in progress were included. Pharmacokinetic data from animals were cited if human data were unavailable. Statistical analyses for all studies were evaluated.

DATA SYNTHESIS

By selectivity targeting D2 receptors, the newer dopamine agonists (i.e., cabergoline, pramipexole, ropinirole) may delay the introduction of levodopa and thus the occurrence of levodopa-induced dyskinesias. In addition, they are efficacious as adjunctive therapies in patients with advanced Parkinson's disease. Unlike the currently available dopamine agonists, pramipexole and ropinirole are non-ergot derivatives and do not cause skin inflammation, paresthesias, pulmonary infiltrates, or pleural effusion. The COMT inhibitors, tolcapone and entacapone, improve the pharmacokinetics of levodopa by preventing its peripheral catabolism and increasing the concentration of brain dopamine; thus, these agents may reduce the incidence of "wearing-off" effects associated with the short half-life of levodopa and the progression of Parkinson's disease.

CONCLUSIONS

Interim 6-month analyses of pramipexole, ropinirole, and cabergoline for symptomatic treatment of early Parkinson's disease have shown these drugs to be efficacious and relatively well-tolerated when used as monotherapy. Their role in delaying the development of motor fluctuations and delaying the addition of levodopa is the subject of long-term clinical studies. In advanced stages of Parkinson's disease, these medications were also efficacious; however, the main adverse effects included dyskinesias, somnolence, and hallucinations. The COMT inhibitors, entacapone and tolcapone, have also demonstrated efficacy in improving on-time in patients with stable disease. Tolcapone has also demonstrated efficacy in patients with motor fluctuations. Both drugs are relatively well-tolerated, with the exception of dyskinesias that require reduction of the levodopa dosage and occasional diarrhea.