Which risk factors predict the levodopa response in fluctuating Parkinson's disease?

Levodopa in the treatment of Parkinson's disease

Levodopa is the most efficacious drug to treat the symptoms of Parkinson's disease (PD) and is widely considered the "gold standard" by which to compare other therapies, including surgical therapy. Response to levodopa is one of the criteria for the clinical diagnosis of PD. A major limiting factor in levodopa therapy is the development of motor complications, namely dyskinesias and motor fluctuations. The ELLDOPA study was designed to determine if levodopa affected the progression of PD. This double-blind randomized study showed that the subjects treated with levodopa for 40 weeks had less severe parkinsonism than the placebo treated subjects even after a 2-week washout of medications, with the highest dose group showing the greatest benefit. Thus, levodopa may actually have neuroprotective value, but the result was not conclusive of slowing disease progression, because the same result could have arisen from a very long-lasting symptomatic benefit of levodopa.

Levodopa-induced response fluctuations in patients with Parkinson's disease: strategies for management

Fluctuations in response to levodopa in patients in the advanced stages of idiopathic Parkinson's disease occur frequently and are a difficult problem to treat. Patients who are treated with levodopa have an additional 10% risk of experiencing response fluctuations with each year of treatment: 50% of patients have this problem after 5 years of receiving levodopa therapy and almost 100% of patients after 10 years. The mechanisms by which response fluctuations occur are only partially understood and can be divided into three main types: (i) presynaptic neuronal degeneration leading to a lack of buffering of released levodopa, which is mainly related to wearing-off phenomena; (ii) postsynaptic changes in dopamine receptor sensitivity and number, partially caused by the presynaptic changes, which are clinically related to at-random response fluctuations; and (iii) pharmacokinetic and pharmacodynamic influences of exogenously administered dopaminergic agents. Several oral and parenteral treatment strategies are recommended to manage response fluctuations, such as optimisation of dopamine receptor agonist therapy in combination with a reduction of the levodopa load; use of slow-release levodopa formulations; use of catechol-O-methyltransferase inhibitors; an increase of levodopa dose frequency; use of high-dose amantadine; and intermittent or continuous use of apomorphine and/or levodopa. Continuous stimulation of dopamine receptors with dopaminergic agents is one of the crucial basic steps in the treatment of patients at an advanced stage of Parkinson's disease, and the preferential use of dopamine receptor agonists has proven to be successful in the prevention and treatment of response fluctuations.

Detection and assessment of the severity of levodopa-induced dyskinesia in patients with Parkinson's disease by neural networks

Levodopa-induced dyskinesias (LID) in Parkinson's disease (PD) have remained a clinical challenge. We evaluated the feasibility of neural networks to detect LID and to quantify their severity in 16 patients with PD at rest and during various activities of daily living. The movements of the patients were measured using four pairs of accelerometers mounted on the wrist, upper arm, trunk, and leg on the most affected side. Using parameters obtained from the accelerometer signals, neural networks were trained to detect and to classify LID corresponding to the modified Abnormal Involuntary Movement Scale. Important parameters for classification appeared to be the mean segment velocity and the cross-correlation between accelerometers on the arm, trunk, and leg. Neural networks were able to distinguish voluntary movements from LID and to assess the severity of LID in various activities. Based on the results in this study, we conclude that neural networks are a valid and reliable method to detect and to assess the severity of LID corresponding to the modified Abnormal Involuntary Movement Scale.

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.

Motor fluctuations in Parkinson's disease

OBJECTIVES

To assess patterns, prevalence, and risk factors of motor fluctuations in an unselected population of Parkinson's disease patients attending Movement Disorders Clinic of a tertiary hospital.

MATERIAL AND METHODS

Eighty patients with Parkinson's disease were interviewed and data about their clinical characteristics, motor fluctuations, i.e. dyskinesia, dystonia, motor blocks and details of drug therapy, were collected.

RESULTS

Forty patients had at least one type of motor fluctuation. Twenty three patients had motor blocks, 20 had dyskinesia and 11 had dystonia. Interval between onset of symptom and start of levodopa therapy and duration of levodopa therapy correlated with presence of motor fluctuations in general and to dyskinesia in particular. Patients with dyskinesia had younger age of onset of disease. Motor blocks showed a positive relationship to duration of disease.

CONCLUSIONS

Fifty percent of unselected patients of Parkinson's disease had motor fluctuations after a mean duration of 5 years of illness. Early initiation and longer duration of levodopa therapy were identified as risk factors for motor fluctuations. Younger patients had more risk of developing dyskinesias. Motor blocks were more common in patients with a longer duration of illness.

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.

Q10 therapy in patients with idiopathic Parkinson's disease

A 3-month open-label trial was performed to evaluate the efficacy of 200 mg Q10 daily in 10 patients with Parkinson's disease. Motor performance was assessed with UPDRS and motor tests. There was no significant effect on the clinical ratings.

Quantitative gait analysis in patients with vascular parkinsonism

Until now the clinical criteria for the diagnosis of vascular parkinsonism (VP) have been disputed. The purpose of the present study is to investigate whether quantitative gait analysis can differentiate between the gait pattern of patients with VP and the gait pattern of patients with idiopathic Parkinson's disease (PD). Twelve patients with VP, 12 patients with PD, and 10 neurologically nondiseased controls were examined by quantitative gait analysis. Patients with VP, having a similar gait velocity and stride length, showed relatively preserved arm swing with markedly more anteflexion in the shoulder on the forward sway of the arm swing than patients with PD. Patients with VP also showed less flexion dystonic posture of the elbow, hip, knee, and trunk than did patients with PD. There was no significant difference in the excursions and coordination of arm swing in the patients with VP compared with the control group. Both patient groups showed reduced leg movements, reduced hip extension, and reduced knee flexion and extension as compared with the controls.

Effect of age and disease duration on parkinsonian motor scores under levodopa therapy

One hundred and fifty patients suffering from Parkinson's disease were analysed for the expression of the motor symptoms during optimum response to levodopa therapy (subscale III of the Unified-Parkinson's Disease Rating Scale). Patients were grouped according to age (< or = 64, 65-74, > or = 75 years). Disease duration and daily levodopa dosage were similar in the three groups. Pooled residual scores for posture and gait impairment (PGI), tremor (T), rigidity (R) and distal motor impairment (DMI; hand and foot movements) increased with age (Kruskal-Wallis ANOVA). The parkinsonian scores were significantly higher than the scores of 150 age-matched normal controls (Mann-Whitney U test). The differences between the patients' scores and the scores of the age-matched controls increased with age. In spite of a significant increase in the daily levodopa dosage with disease duration (linear regression), PGI aggravated age-dependently, and DMI age-independently with symptom duration (Spearman rank correlation). In contrast, T and R did not increase with disease duration.

A randomised controlled study comparing bromocriptine to which levodopa was later added, with levodopa alone in previously untreated patients with Parkinson's disease: a five year follow up

This pilot study was performed to compare the occurrence of long term motor complications in Parkinson's disease when the introduction of levodopa was delayed by an initial treatment with high doses of bromocriptine alone. The trial was a prospective randomised controlled study comparing 31 previously untreated patients with Parkinson's disease initially given bromocriptine alone to which levodopa was later added (group B/D) and 29 other previously untreated patients with Parkinson's disease immediately given levodopa alone (group D). The end point was the occurrence of the first motor complications (wearing off or dyskinesia). Group B/D patients received bromocriptine (52 (SEM 5) mg/day) for 2.7 years, to which levodopa was later added (471 (SEM 46) mg/day). Group D patients received a comparable dose of levodopa alone (569 (SEM 47) mg/day). Both had similar disability scores at the end of the study. Motor complications were fewer and appeared later in group B/D than in group D (56% after 4.9 (SEM 0.5) years of treatment v 90% after 2.7 (SEM 0.5) years, p < 0.01). Wearing off appeared later (p < 0.01) in group B/D (4.5 (SEM 0.6) years) than in group D (2.9 (SEM 0.6) years). Peak dose dyskinesia occurred less often in group B/D patients (three v 14 cases, p < 0.01). This study showed that a three year initial monotherapy with high doses of bromocriptine followed by addition of levodopa delayed the occurrence of long term motor complications usually found in patients with Parkinson's disease treated with levodopa alone from the beginning.

Motor response to apomorphine and levodopa in asymmetric Parkinson's disease

The motor responses of 14 patients with Parkinson's disease (six previously untreated and eight chronically receiving levodopa) with pronounced asymmetry in the severity of motor signs between the left and right sides of the body were studied. The effects of a short (60 minutes) and a long (16-22 hours) intravenous levodopa infusion as well as of subcutaneous apomorphine (1-6 mg bolus) were assessed. Four different tapping tests were used to measure motor function. For all pharmacological tests, the more affected side showed a shorter response duration, increased latency, and greater response magnitude than the less affected side. These differences were more pronounced in those patients receiving chronic levodopa treatment. As apomorphine is not dependent on dopamine storage capacity, these findings suggest that postsynaptic mechanisms play an important part in the origin of motor fluctuations in Parkinson's disease.

Impaired cognitive shifting in parkinsonian patients on anticholinergic therapy

In this study we established that cognitive shifting, an ability that is known to be affected in PD, is more impaired in PD patients, treated with anticholinergics, than in de novo patients. Eleven PD patients on anticholinergic monotherapy were compared with 30 de novo patients. The groups did not differ with respect to age, duration and severity of PD, and depression, nor with respect to general intelligence or attention. We assessed cognitive shifting with three different card-sorting tests. The patients on anticholinergics showed a poorer performance on all card-sorting tests than the de novo patients did. The patients on anticholinergics needed significantly more trials in two card-sorting tests and discovered significantly less categories in total. There was also a significant difference in memory performance, but memory performance did not correlate with any score on the card-sorting tests. This indicates that the performance on card-sorting tests and the memory performance were independent.

Repeated L-dopa administration reduces the ability of dopamine storage and abolishes the supersensitivity of dopamine receptors in the striatum of intact rat

The "wearing-off" phenomenon is a clinically recognized adverse effect of long-term L-DOPA therapy in Parkinson's disease. Several causes of this phenomenon have been proposed, but no direct evidence has yet been obtained. The present study was therefore conducted to investigate the effects of long-term L-DOPA administration on the dopamine system. We examined in rats the time course of the levels of L-DOPA and its metabolites in the serum and striatum, the activities of tyrosine hydroxylase and catechol O-methyltransferase, and the D1 and D2 dopamine receptor bindings in the striatum until 12 h after the final dose on the 28th day of repeated oral L-DOPA administration, and compared the results with those after a single L-DOPA administration. The results revealed that long-term L-DOPA administration induced (1) acceleration of DOPA absorption at the gut and the blood-brain barrier, (2) reduction of dopamine retention in the striatum, and (3) loss of "supersensitive response" of dopamine receptors. "Supersensitive response" induced by single L-DOPA administration was preceded by the increase of D1 messenger RNA. We suggest that these changes after long-term L-DOPA administration are causes of the "wearing-off" phenomenon in Parkinson's disease.