Lisuride infusion pump: a device for the treatment of motor fluctuations in Parkinson's disease

L-DOPA-therapy in Parkinson's disease: some personal reflections on L-DOPA therapy from Vienna and Berlin

Dopamine was initially considered as a mere intermediate in the noradrenaline synthesis but was then found to be a neurotransmitter. Its depletion resulted in characteristic symptoms in experimental studies and could be antagonized by DOPA (3,4-dihydroxyphenylalanin), suggesting a similarity to the human disorder Parkinson´s disease (PD) and a therapeutic potential which was successfully exploited from the 1970s on. This was due to the pioneering work of Arvid Carlsson and clinicians around the world who first worked on the breakthrough of L-DOPA therapy and then on its amendment and modification and on alternative therapies for PD patients. All these developments led to the establishment of PD therapy as we know it today. It is characterized by the availability of many different compounds which are mostly employed in combination and by different methods: orally, intravenously, transdermally, subcutaneously, or duodenally. Here, we present without claim of completeness some personal reflections about causal drug developments for PD patients and reflect on some personal interactions with leading clinicians and basic researchers who cooperated with us. Such interactions are crucial for the creation, sometimes serendipitously, of fresh ideas and to further develop existing concepts to make therapeutical progress.

Access to device-aided therapies in advanced Parkinson's disease: navigating clinician biases, patient preference, and prognostic uncertainty

Device-aided therapies (DAT), which include deep brain stimulation and pump-based continuous dopaminergic stimulation with either levodopa or apomorphine, are among the major advances in the clinical management of Parkinson's disease (PD). Although DAT are being increasingly offered earlier in the disease course, their classical indication remains advanced PD. Theoretically, every patient should be offered transition to DAT when faced with refractory motor and nonmotor fluctuations and functional decline. Worldwide clinical reality is far from these ideal, and, therefore, question the "real-world" equal opportunity of access to DAT for PD patients with advanced PD-even within a single health care system. Differences in access to care, referral pattern (timing and frequency), as well as physician biases (unconscious/implicit or conscious/explicit bias), and patients' preferences or health-seeking behaviour are to be considered. Compared to DBS, little information is available concerning infusion therapies, as well as neurologists' and patients' attitudes towards them. This viewpoint aims to be thought-provoking and to assist clinicians in moving through the process of DAT selection, by including in their decision algorithm their own biases, patient perspective, ethical concerns as well as the current unknowns surrounding PD prognosis and DAT-related long-term side effects for a given patient.

Transplantation of Polymer Encapsulated Pc12 Cells: Use of Chitosan as an Immobilization Matrix

Polymer capsules were fabricated to encapsulate PC12 cells within a semipermeable and immunoprotective barrier. The inclusion of precipitated chitosan as an immobilization matrix within the polymer capsules increased the survival and physiological functioning of the PC12 cells. In an initial study, HPLC analysis revealed that the inclusion of a chitosan matrix resulted in an increased output of catecholamines from the encapsulated PC12 cells under both basal conditions, and following high potassium depolarization at 2 and 4 wk following encapsulation in vitro. Furthermore, implantation of cohort PC12 cell-loaded capsules into guinea pig striata revealed that chitosan enhanced PC 12 cell survival after 6 wk. A second study determined that 12 wk after implantation into guinea pig striatum, abundant tyrosine hydroxylase-positive PC12 cells were evenly distributed within capsules containing chitosan. The long-term biocompatibility of these implants was good as determined by the absence of inflammatory or immune cells, and minimal GFAP reactivity surrounding the implant site. In contrast, implantation of unencapsulated PC12 cells resulted in a marked host tissue reaction, and destruction of the implanted cells within 4 wk. It is concluded that the inclusion of precipitated chitosan as an immobilization matrix enhanced the viability of encapsulated PC12 cells, and that altering the internal milieu of polymeric capsules may represent an effective transplant strategy for ameliorating human diseases characterized by secretory cell dysfunction.

Future Treatment of Parkinson’s Disease

New methods of drug delivery and slowing down the progression of Parkinson’s disease (PD) are the major goals of research. More steady drug levels in the blood are possible by means of controlled-release preparations of levodopa and long-acting dopamine agonists, as well as transcutaneous duodenal tubes and pumps for controlled subcutaneous infusion. Patches containing dopamine agonists absorbed through the skin may be developed. The role of D1 agonists as compared with D2 agonists remains to be elucidated. Agonists on autoreceptors of dopaminergic neurons may potentially reduce excessive stimulation of the intact neurons and this may slow down the rate of neuronal death in PD. Monoamine oxidase-B inhibitors may have a potentially protective action on neurons. Investigations are being carried out to evaluate this claim. Catechol-o-methyl-transferase inhibitors may be helpful in theory. There is also recent interest in inhibitors of excitatory amino acids, which may contribute to neuronal loss in PD.

Parkinson's disease-associated melanin steal

Urinary dopamine fluctuations in the competitive inhibition state were first documented in 2009. At that time, it was noted that progressively higher daily dosing values of L-tyrosine decreased the magnitude of these fluctuations. While extensive statistical analysis has been performed by the authors since 2004, it was not until 2012 that a plausible explanation was formulated. In the process, correlations with L-tyrosine administration and the on/off effect of Parkinson's disease were defined. This paper documents the current knowledge with regard to the management of retrograde phase 1 dopamine fluctuations and investigates the hypothesis that they are caused by a melanin steal phenomenon.

Clinical features, pathophysiology, and treatment of levodopa-induced dyskinesias in Parkinson's disease

Dyskinetic disorders are characterized by excess of motor activity that may interfere with normal movement control. In patients with Parkinson's disease, the chronic levodopa treatment induces dyskinetic movements known as levodopa-induced dyskinesias (LID). This paper analyzed the pathophysiology, clinical manifestations, pharmacological treatments, and surgical procedures to treat hyperkinetic disorders. Surgery is currently the only treatment available for Parkinson's disease that may improve both parkinsonian motor syndrome and LID. However, this paper shows the different mechanisms involved are not well understood.

Positron emission tomography imaging demonstrates correlation between behavioral recovery and correction of dopamine neurotransmission after gene therapy

In vivo gene transfer using viral vectors is an emerging therapy for neurodegenerative diseases with a clinical impact recently demonstrated in Parkinson's disease patients. Recombinant adeno-associated viral (rAAV) vectors, in particular, provide an excellent tool for long-term expression of therapeutic genes in the brain. Here we used the [(11)C]raclopride [(S)-(-)-3,5-dichloro-N-((1-ethyl-2-pyrrolidinyl)methyl)-2-hydroxy-6-methoxybenzamide] micro-positron emission tomography (PET) technique to demonstrate that delivery of the tyrosine hydroxylase (TH) and GTP cyclohydrolase 1 (GCH1) enzymes using an rAAV5 vector normalizes the increased [(11)C]raclopride binding in hemiparkinsonian rats. Importantly, we show in vivo by microPET imaging and postmortem by classical binding assays performed in the very same animals that the changes in [(11)C]raclopride after viral vector-based enzyme replacement therapy is attributable to a decrease in the affinity of the tracer binding to the D(2) receptors, providing evidence for reconstitution of a functional pool of endogenous dopamine in the striatum. Moreover, the extent of the normalization in this non-invasive imaging measure was highly correlated with the functional recovery in motor behavior. The PET imaging protocol used in this study is fully adaptable to humans and thus can serve as an in vivo imaging technique to follow TH + GCH1 gene therapy in PD patients and provide an additional objective measure to a potential clinical trial using rAAV vectors to deliver l-3,4-dihydroxyphenylanaline in the brain.

Transdermal rotigotine: a new non-ergot dopamine agonist for the treatment of Parkinson’s disease

An important conceptual development to avoid the occurrence of motor dyskinesias in Parkinson's disease is continuous dopaminergic stimulation. Studies in animal models and humans suggest that continuous dopaminergic stimulation could be achieved by the infusions of different dopamine agonists or levodopa, and may significantly reduce the risk of dyskinesias associated with treatment strategies utilising pulsatile treatment options. However, so far, these techniques have either necessitated frequent intake of oral therapy or invasive parenteral treatment. The rotigotine transdermal delivery system represents a significant development that allows a constant delivery of a non-ergot dopamine agonist using a once-daily regimen, achieving steady plasma levels. Clinical trials demonstrate the efficacy of rotigotine in early and advanced Parkinson's disease, with important implications for treatment of non-motor symptoms of Parkinson's disease.

Dystonia in Parkinson’s disease

Dystonia can occasionally be found in idiopathic Parkinson's disease. It is very uncommon in untreated patients and is more frequently seen as a complication of its treatment. In this review, the various types of dystonia occurring in PD, the differential diagnosis with other parkinsonian syndromes associated with dystonia and treatments available are revised. Dystonia unrelated to treatment can be typical (blepharospasm, torticollis), atypical (parkinsonian writer's cramp, camptocormia, anismus), or occurring in earlyonset Parkinson disease (the so-called kinesigenic foot dystonia, considered a hallmark of early-onset Parkinson's disease). Early and prominent dystonia in untreated patients with parkinsonism should raise the suspicion of other entities other than Parkinson's disease, such as progressive supranuclear palsy, multiple system atrophy or corticobasal degeneration. In patients on chronic dopaminergic treatment, peak-dose dystonia, diphasic dystonia and off-dystonia can be seen. The later constitutes the major dystonic feature of chronic levodopa therapy, and a wide variety of strategies are available to manage this complication. Among them, deep brain stimulation of the subthalamic nucleus has proved to be the most effective one. Dystonic reactions (mainly involving oculomotor cranial nerves and limbs) in operated patients (especially carriers of deep brain stimulation (DBS) devices) are increasingly being reported, constituting a new type of dystonia in patients with Parkinson's disease: dystonia linked to surgical treatment.

Pathophysiology of motor fluctuations in Parkinson's disease

Loss of dopamine neurons in Parkinson's disease (PD) initiates a complex stream of effects that results in the development of tremor, bradykinesia, and rigidity. While levodopa remains the most effective drug for the symptomatic treatment of PD, its chronic administration is associated with the development of motor fluctuations and dyskinesias. The risk of developing motor fluctuations has been linked to disease severity, dosage of levodopa, and the age of the patient. A recent body of preclinical data has demonstrated that alterations in dopaminergic tone as well as in treatment patterns results in cellular adaptations, including alterations in gene expression. This body of preclinical data suggests that nonphysiological, pulsatile stimulation of dopamine receptors induces the development of motor fluctuations and dyskinesias and raises the possibility that nonpulsatile stimulation of dopamine receptors (continuous dopaminergic stimulation) might induce fewer fluctuations. We discuss the theory of continuous dopaminergic stimulation and its implications for the management of motor fluctuations in patients with advanced and early PD.

Continuous subcutaneous apomorphine therapy improves dyskinesias in Parkinson's disease: a prospective study using single-dose challenges

Continuous subcutaneous (SC) infusion of the dopamine agonist apomorphine was shown in retrospective studies to improve drug-induced dyskinesias in Parkinson's disease (PD). We prospectively assessed the antidyskinetic effect of continuous SC apomorphine therapy using subjective and objective measures, and sought to determine whether any observed dyskinesia reduction could be corroborated using single-dose dopaminergic challenges. Twelve PD patients with on-off fluctuations and disabling dyskinesias who were scheduled to start apomorphine pump treatment underwent acute levodopa and apomorphine challenges at baseline and 6 months later. Video recordings involving motor tasks were rated blindly by two independent raters using modified AIMS and Goetz dyskinesia scales. At 6 months, mean apomorphine dose was 75.2 mg per day and the mean L-dopa dose had been reduced by 55%. Daily off time in patients' diaries was reduced by 38% (2.4 hours). The L-dopa challenges showed a reduction of 44% in AIMS and 40% in Goetz scores (both P < 0.01). Apomorphine challenges showed a reduction of 39% in AIMS and 36% in Goetz scores (both P < 0.01). Patients' self-assessment scores reflected these significant changes. Dyskinesia improvement correlated with reduction in oral medication and with the final apomorphine dose (P < 0.05). This prospective study confirms marked dyskinesia reduction on continuous subcutaneous apomorphine therapy, paralleled by reduced dyskinesias during dopaminergic challenge tests. Our findings support the concept that replacement of short-acting oral antiparkinsonian medication with continuous dopamine receptor stimulation may reverse, at least partially, the sensitization process believed to mediate the development of drug-induced dyskinesias in PD.

Presynaptic mechanisms of motor fluctuations in Parkinson’s disease: a probabilistic model

Levodopa-treated Parkinson's disease is often complicated by the occurrence of motor fluctuations, which can be predictable ('wearing-off') or unpredictable ('on-off'). In contrast, untreated dopa-responsive dystonia (DRD) is usually characterized by predictable diurnal fluctuation. The pathogenesis of motor fluctuations in treated Parkinson's disease and diurnal fluctuation in untreated DRD is poorly understood. We have developed a mathematical model indicating that all these fluctuations in motor function can be explained by presynaptic mechanisms. The model is predicated upon the release of dopamine being subject to probabilistic variations in the quantity of dopamine released by exocytosis of vesicles. Specifically, we propose that the concentration of intravesicular dopamine undergoes dynamic changes according to a log-normal distribution that is associated with different probabilities of release failure. Changes in two parameters, (i) the proportion of vesicles that undergo exocytosis per unit of time and (ii) the proportion of dopamine subject to re-uptake from the synapse, allowed us to model different curves of levodopa response, for the same degree of nigrostriatal damage in Parkinson's disease. The model predicts the following periods of levodopa clinical benefit: 4 h for stable responders, 3 h for wearing-off fluctuators, and 1.5 h for on-off fluctuators. The model also predicts that diurnal fluctuation in untreated DRD should occur some 8 h after getting up in the morning. All these results fit well with clinical observations. Additionally, we calculated the probability of obtaining a second ON period after a single dose of levodopa in Parkinson's disease (the 'yo-yoing' phenomenon). The model shows that the yo-yoing phenomenon depends on how fast the curve crosses the threshold that separates ON and OFF states, which explains why this phenomenon is virtually exclusive to patients with on-off fluctuations. The model supports the idea that presynaptic mechanisms play a key role in both short-duration and long-duration responses encountered in Parkinson's disease. Dyskinesias may also be explained by the same mechanisms.

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.

Effects of ropinirole on motor behavior in MPTP-treated common marmosets

The effects of ropinirole (4-[2-(dipropylamino)ethyl]-2-indolinone monohydrochloride), a nonergoline dopamine receptor agonist with a high affinity for native dopamine D(2)-like receptors, on Parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 2.5 mg/animal in common marmosets were examined and compared to the effects of bromocriptine. Ropinirole (0.1-3 mg/kg, PO) increased motor activity dose dependently and reversed akinesia or uncoordinated movement in MPTP-treated marmosets. The activities for ropinirole were very similar to those of bromocriptine. Ropinirole had, however, several properties that differed from those of bromocriptine. Ropinirole caused a more rapid onset of anti-Parkinsonian activity compared to bromocriptine, and had a potency more than five times greater than that of bromocriptine in the improvement of motor deficits. The combination of ropinirole and L-DOPA increased the effectiveness of ropinirole or L-DOPA alone, and produced a more marked additive effect on motor activity than did bromocriptine and L-DOPA. Chronic administration of ropinirole for 21 days produced a statistically significant increase in motor activity compared to the initial administration, and akinesia scores, measured through rating the quality of movements, were also improved without obvious dyskinesia. This study suggests that ropinirole is a dopamine D(2)-like receptor agonistic drug of potential use in the treatment of Parkinson's disease.

In vitro and in vivo long term release of apomorphine from polymer matrices

Since apomorphine actually reveals high efficacy in treatment of Parkinson's disease but only has a very short half life, it is of only limited clinical significance. To overcome this substantial disadvantage, drug application by long term delivery systems could be one possibility. Based on this background, ethylene vinyl acetate polymeric delivery systems were manufactured that differed in size, with either coated or uncoated surfaces, but were similar in apomorphine loading. Release from uncoated polymeric delivery systems followed first order kinetics, whereas coated polymeric delivery systems showed within the first 40 days a period of first order kinetics release, in which the release rate is approximately half that of the uncoated polymeric delivery systems, followed by a zero order kinetics release for more than 130 days with a daily release rate of 3.1 +/- 0.2 mg. In vivo release was investigated by determining plasma apomorphine concentrations after implanting polymeric delivery systems into the abdominal cavities of rats. Animals with uncoated polymeric delivery systems exhibited symptoms of an apomorphin overdosage within 20 days after surgery. Using coated polymeric delivery systems, a steady state plasma concentration of 15 ng/ml was observed, which was maintained over a period of 130 days after an initial period of high plasma concentrations. Based on our results, it is concluded that polymeric delivery systems might be an appropriate method for applying apomorphine for the treatment of Parkinson's disease.

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 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.

Continuous subcutaneous waking day apomorphine in the long term treatment of levodopa induced interdose dyskinesias in Parkinson's disease

OBJECTIVES

To determine whether continuous waking day dopaminergic stimulation with the dopamine agonist apomorphine can reduce levodopa induced dyskinesias in Parkinson's disease

METHODS

19 patients with severe unpredictable refractory motor fluctuations and functionally disabling levodopa induced dyskinesias were treated with continuous subcutaneous apomorphine monotherapy for a minimum duration of 2.7 years

RESULTS

A mean 65% reduction in dyskinetic severity and a mean 85% reduction in frequency and duration occurred. On discontinuing levodopa a concomitant reduction in off period time was also seen (35% of waking day "off" reduced to 10%)

CONCLUSION

Continuous waking day dopaminergic stimulation with apomorphine reset the threshold for dyskinesias and led to a pronounced reduction in their frequency. Apomorphine should be considered as a less invasive alternative to pallidotomy or deep cerebral stimulation in controlling levodopa induced interdose dose dyskinesias.

"Off" painful dystonia in Parkinson's disease treated with botulinum toxin

The "off" painful dystonia (OPD), usually concerning the feet, is a type of abnormal involuntary movement, induced by the chronic use of levodopa. It is mostly observed in the advanced stage of Parkinson's disease (PD), particularly in the early morning, in the evening, and late at night. Indeed, some patients have experienced OPD also during "on" periods when dystonic posture of the foot alternates with dyskinesia. The pain probably is due to sustained muscle contraction, which causes prolonged muscle spasm, as in primary dystonia or torticollis. Dopaminergic drugs like bromocriptine, pergolide, and especially apomorphine (s.c. infusions, or bolus), can dramatically improve the OPD. Anticholinergics baclofen and lithium are alos used in the management of OPD with some benefit. On the other hand, clinical experience shows that in many cases, these therapeutic procedures are not always enough to produce the expected results. Thirty PD patients (22 men and eight women) with OPD of the foot were treated with botulinum toxin (Botox, Btx) using electromyograms to guide injections. Dystonia was evaluated using a quantitative rating scale. The selection of the muscles for Btx treatment was carried out on the basis of foot posture. We injected Btx into tibialis posterior, tibialis anterior, gastrocnemius, flexor digitorum longus, and extensores hallucis longus with a median dose 40 IU for each muscle, distributed in two sites. In all patients, the pain improved within 10 days, whereas in 21 patients, the pain disappeared completely for 4 months (range, 3-7 months); a concomitant improvement in intensity of the dystonic spasm was also observed. No side effects were reported. Seven patients with associated "on" foot dystonia described an improvement of foot posture on walking. In conclusion, in this uncontrolled study, the use of Btx in OPD seemed a promising tool to improve pain linked to foot dystonia; however, because of the well-known underlying dopaminergic defect in OPD, the Btx therapy should be considered only if the dopaminergic treatment established for the management of OPD has failed.

Apomorphine in patients with Parkinson's disease

We present a review of the recent literature and personal experience with apomorphine in patients with Parkinson's disease. Apomorphine is a potent D1 and D2 dopaminergic agonist. It has a rapid and short duration effect after subcutaneous administration at doses ranging from 15 to 180 micrograms/kg. Plasma maximal concentration is reached in 8-16 minutes, with a plasma half life of 34-70 minutes. Bioavailability is close to 100%. Repeated injections in patients show post-stimulative hyposensitivity. Apomorphine test appears very useful for the differential diagnosis between idiopathic Parkinson's disease and other Parkinson plus syndromes, and as a predictive test for dopaminergic responsiveness. Appropriate doses are able to alleviate akinesia, rigidity and tremor. Recent therapeutic trials have demonstrated the high interest of intermittent multiple subcutaneous apomorphine injections to cut the "off" motor phases in fluctuating parkinsonian patients under chronic levodopa treatment. In some cases, continuous apomorphine subcutaneous infusion with a portable pump may be required, particularly when levodopa treatment is temporarily interrupted, as after abdominal surgery. During long-term treatment, the apomorphine dose able to relieve akinesia remains stable. Peripheral side effects such as nausea and hypotension may be prevented by the co-administration of domperidone, a peripheral dopaminergic antagonist. Cutaneous fibrous nodules and psychiatric symptoms may occur, but usually at high dosages with continuous infusion. Local allergic effects have limited the use of other routes of administration, such as intranasal, sublingual, and rectal routes. Apomorphine is also used as a pharmacological tool for clinical research with the aim of a better understanding of the pathophysiology of Parkinson's disease.

Subcutaneous apomorphine infusion in Parkinson's disease: does it have a role?

Apomorphine is a potent dopamine agonist at both D1 and D2 receptors and has been used successfully for treating the 'on/off' phenomenon in Parkinson's disease. We report our experience with apomorphine in treating the 'on/off' phenomenon in L-dopa responsive idiopathic Parkinson's disease. Thirteen such patients were commenced on apomorphine infusions. Their mean age was 69 (range 53-80) years and the mean duration of the disease was 15 (range 6-28) years. The clinical response to apomorphine was good in four patients, fair in two, unchanged in five and worse in two. Activities of daily living improved in six, were unchanged in five and worse in two. When the response was poor or showed no change, apomorphine was discontinued. In addition, apomorphine was also discontinued in three patients who had had a fair/good response but suffered side effects of hallucinations, delusions and psychosis, lack of cooperation or found the pump inconvenient. Apomorphine was continued in only three patients out of 13.

Quantitative determination of the dopamine agonist lisuride in plasma using high-performance liquid chromatography with fluorescence detection

An HPLC method for the determination of lisuride hydrogen maleate in plasma is described. After addition of ergotamine tartrate as internal standard, plasma is extracted with diethyl ether. Following evaporation of the solvent and redissolving in methanol the extract is injected on a silica HPLC column and lisuride is monitored by fluorescence detection using an excitation wavelength of 322 nm and an emission wavelength of 405 nm. The method is sufficiently accurate and precise with a detection limit of 20 pg/ml lisuride in plasma. The usefulness of the method is demonstrated by measurements of lisuride levels after oral intake of a 0.6 mg dose of the drug by a healthy male volunteer, showing a peak level of 1266 pg/ml, 45 min after intake.

Long-term observation of chronic subcutaneous administration of lisuride in the treatment of motor fluctuations in Parkinson's disease

Twenty-nine patients with advanced Parkinson's disease were treated with subcutaneous lisuride infusion in addition to a basic therapy consisting of levodopa + PDI in all, and deprenyl in some patients. At the time of the report, 13 patients are still receiving lisuride infusion after 5-36 months, while 16 have dropped out after 0.5-30 months: one because of psychosis, three because of insufficient efficacy, three due to death unrelated to treatment, three because of difficulties in handling the pump as outpatients, and six for other reasons. "Off"-periods and Parkinsonian disability in "off" and in "on" were reduced significantly. These improvements remained constant throughout the observation period. Once the optimal dose regimen is established, only minor adjustments of the doses of lisuride and levodopa are required in the individual case.

Continuous subcutaneous lisuride infusion in OPCA

Four patients with sporadic olivopontocerebellar atrophy (OPCA) and severe signs of Parkinsonism received continuous subcutaneous lisuride infusion via a small external pump. All 4 patients benefitted from this treatment: 3 showed an overall improvement in motor performance, in 1 patient mainly dysphagia and dysarthria improved. Therapeutic benefit lasted for at least 6 months of follow up. With a daily dose of 1.0 mg subcutaneous lisuride, treatment limitations were reached in the form of dysphagia, probably due to oropharyngeal dystonia. Subcutaneous lisuride infusion should be taken into consideration in OPCA patients with signs of Parkinsonism if oral dopaminergic treatment has failed earlier on.

Antiparkinsonian dopamine agonists: a review of the pharmacokinetics and neuropharmacology in animals and humans

With the intention of compensating for the deficit of endogenous dopamine (DA) in the basal ganglia of Parkinsonian patients by substitution with agents which directly stimulate central DA receptors, synthetic DA agonists have been introduced almost 20 years ago for the symptomatic treatment of Parkinson's disease. The original expectation that DA agonists would be able to completely restore extrapyramidal motor function in Parkinsonian patients has turned out as too mechanistic and simplicative. However, undoubtedly DA agonists have improved therapeutic possibilities in Parkinson's disease. Thus, clinical evidence from controlled chronic studies in patients indicates that the therapeutic results following the early application of DA agonists in combination with L-DOPA on a long-term base are superior to the respective monotherapy. However, none of the DA agonists currently employed for antiparkinsonian treatment i.e. apomorphine and the ergoline derivatives bromocriptine, lisuride and pergolide, is optimal with respect to pharmacokinetic properties (poor oral bioavailability with considerable intra- and interindividual variation) or pharmacological profiles (low selectivity for DA receptors in case of the ergot agonists). The pathophysiology underlying Parkinson's disease which turned out more complex than initially expected might provide another explanation for the limited therapeutic potential of DA agonists. Therefore, apart from summarizing the pharmacokinetics, biotransformation, neuropharmacology and neurobiochemistry of the DA agonists employed clinically, the present article also reviews physiological aspects of (a) central dopaminergic neurotransmission including the topographical distribution of DA receptor subtypes and their functional significance, (b) the intracellular signal processing in striatal output neurons and (c) the intraneuronal mechanisms which integrate the various neurotransmitter signals converging on the striatal output neuron to a demand-adjusted effector cell response via the cross-talk between the different second messenger systems. Based on these considerations, potential pharmacological approaches for the development of improved antiparkinsonian drugs are outlined. There is a therapeutic demand for more selective and better bioavailable DA agonists. In particular, selective D-1 receptor agonists are highly desirable to provide a more specific probe than SKF 38 393 for clarifying the current controversy on the disparate findings in nonprimate species and monkeys or Parkinsonian patients, respectively, regarding the functional significance of D-1 receptors for the antiparkinsonian action of DA agonists or L-DOPA. The therapeutic importance of D-2 receptor activation is generally accepted; whether DA agonists combining a balanced affinity to both D-1 and D-2 receptors within one molecule (to some extent a property of apomorphine) might be superior to subtype-specific DA agonists remains to be tested clinically.(ABSTRACT TRUNCATED AT 400 WORDS)

Behavioral complications of drug treatment of Parkinson's disease

A variety of neuropharmacologic agents, including anticholinergic drugs, amantadine hydrochloride, levodopa, selegiline, bromocriptine, and pergolide, are now available for the treatment of Parkinson's disease. Of patients treated with dopaminergic agents, 30% develop visual hallucinations, 10% exhibit delusions, 10% have euphoria, 1% have mania, 10% to 15% experience increased anxiety, 15% have confusional periods, and a few exhibit altered sexual behavior. Anticholinergic drugs have a greater tendency to produce confusional states than dopaminergic compounds. Elderly patients and those with underlying dementia are most likely to have untoward side effects with anti-parkinsonism treatment. Dosage reduction is the optimum management strategy, although anti-psychotic agents may be necessary in patients with delusions, and lithium may help control drug-induced mania. Dopaminergic agents share the property of stimulation of D2 dopamine receptors, and this action may play an essential role in mediating their neuropsychiatric effects.

Immunoelectron microscopic analysis of the synaptic connectivity of serotoninergic neurons grafted to the 5,7-dihydroxytryptamine-lesioned rat spinal cord

The connections between the host and 5-hydroxytryptamine-containing neurons grafted to the spinal cord have been analysed using electron microscopic immunohistochemistry. Adult rats with 5,7-dihydroxytryptamine lesions of the brain and spinal cord received implants of embryonic medullary raphé neurons at three sites in the spinal cord. Eight to 10 months after grafting, the transplanted 5-hydroxytryptamine-positive neurons had formed extensive and complex contacts with spines, dendrites, perikarya and vesicle-containing structures in both the dorsal and ventral horns. Reinnervation of laminae IV-VI was less rich. In the graft itself, connections were also made between non-immunoreactive varicosities and 5-hydroxytryptamine-containing dendrites, and somata, but the exact origin of the afferents was not determined. Outside the implant site, no obvious synaptic junctions onto grafted 5-hydroxytryptamine-immunoreactive boutons were obvious, although labelled and unlabelled varicosities were often in close apposition. Synaptic junctions in the dorsal horn were predominantly symmetric, with the presynaptic varicosity containing mostly small agranular vesicles. By contrast, in the ventral horn most junctions were asymmetric, while the presynaptic element contained both small agranular and large dense-core vesicles. The results demonstrate that the types of synaptic contacts formed between the grafted 5-hydroxytryptamine neurons and the host spinal cord are remarkably similar to those found in intact spinal cord. In addition, the division of morphological differences that exists between 5-hydroxytryptamine-containing boutons in the normal dorsal vs ventral horns is also apparent in the transplanted animals. Finally, there appear to be present several anatomical substrates for the regulation by the host of 5-hydroxytryptamine output from the grafted neurons.

Preclinical pharmacology of ropinirole (SK&F 101468-A) a novel dopamine D2 agonist

These studies characterise the pharmacology of ropinirole, a selective D-2 agonist. High-affinity human caudate binding revealed a Ki for D2 receptors of 2.9 x 10(-8) M with no affinity for D1 at 10(-4) M in the rat. Ropinirole was weakly active at alpha 2-adrenoceptors and 5-HT2 receptors but inactive at 5-HT1, benzodiazepine and gamma-aminobutyric acid receptors or alpha 1 and beta-adrenoceptors. In rodents, ropinirole, like apomorphine, caused biphasic spontaneous locomotor activity and contralateral circling in 6-OHDA-lesioned mice with no tolerance to the latter after 14 days treatment. Amphetamine caused ipsilateral responses in the lesioned mice. Ropinirole did not cause marked stereotypies. In marmosets ropinirole (0.05-1.0 mg/kg SC or 0.1 mg/kg PO) reversed all motor and behavioural deficits induced by MPTP. This response started 10-20 minutes after dosing, and exceeded 2 hours. No tolerance was seen following chronic b.i.d. treatment. Similar results were obtained with 1-dopa plus benserazide; however, 1-dopa always caused emesis, whereas beneficial effects were shown with ropinirole in the absence of this side effect. These results support the continued clinical assessment of ropinirole for the treatment of Parkinson's disease.

Intracerebral adrenal medulla grafts: a review

This review summarizes basic and clinical research on intracerebral adrenal medulla grafts, emphasizing potential applications to Parkinson's disease. Properties of intraventricular and intraparenchymal grafts are described, and cell survival and functional effects are compared. It is clear that adrenal medulla allografts survive poorly in the parenchyma of the corpus striatum and better in the lateral ventricle. Nerve growth factor (NGF) may improve the survival of adrenal medulla grafts. In the absence of added NGF even adrenal medulla grafts in the ventricle survive irregularly, and the factors required for graft survival in the ventricle are not well understood. In the 6-hydroxydopamine-lesioned rat model most evidence suggests, not surprisingly, that adrenal medulla grafts produce functional effects only when they survive. These effects may be related to production of catecholamines by the transplanted cells. In addition, adrenal medulla grafts may produce trophic effects on host brain. These effects are most evident in animals with MPTP-induced damage to dopaminergic systems and may be nonspecific, possibly related in part to the brain injury that is induced by graft implantation. Trophic effects may contribute to the functional effects of adrenal medulla grafts: For intraparenchymal grafts, trophic effects that do not require cell survival may contribute small functional changes, while additional behavioral effects may require substantial chromaffin cell survival. The evidence for direct dopamine-mediated effects as compared to trophic mechanisms of action for these grafts in animal models for Parkinson's disease is presented. Clinical studies of adrenal medulla grafts in human patients are examined and compared in detail. When inspected closely, the various clinical studies are in general agreement on most points, although there are differences in the degree of improvement found, both across different studies and individual patients. It is concluded that some beneficial clinical effects occur, with small to modest changes in most patients and substantial improvement in a minority of patients. There also seem to be larger or more consistent changes in durations of "on" and "off" times in L-dihydroxyphenylalanine-treated patients. There are substantial side effects, and it is not clear that the clinical changes are sufficient to justify performing adrenal medulla transplantation in human patients as a routine procedure.(ABSTRACT TRUNCATED AT 400 WORDS)

Extended levodopa release from a subcutaneously implanted polymer matrix in rats

It is well recognized that plasma fluctuations resulting from oral levodopa therapy may cause an unstable clinical response in parkinsonian patients. We have therefore developed a slow-release polymer matrix system that can deliver levodopa continuously for extended periods of time (at least 225 days) after subcutaneous implantation in rats. Advantages of this approach include (1) the elimination of levodopa plasma fluctuations and (2) the possibility of reducing the required dose due to constant plasma levels and because the gastrointestinal tract is circumvented. The peripheral implantation of polymer systems containing levodopa, dopamine receptor agonists, or other anti-Parkinson agents may constitute a novel technology of drug delivery to improve the care of patients with Parkinson's disease.

Nasogastric and intravenous infusions of (+)-4-propyl-9-hydroxynaphthoxazine (PHNO) in Parkinson's disease

(+)-4-propyl-9-hydroxynaphthoxazine (PHNO) is a new dopamine agonist which is capable of producing a sustained response in parkinsonian patients with "on-off" fluctuations when given as a continuous infusion either nasogastrically or intravenously. These data suggest that a sustained release formulation of PHNO may provide a significant, new treatment for patients with "on-off" fluctuations.

Dopaminergic responsiveness to apomorphine after chronic treatment with subcutaneous lisuride infusion in Parkinson's disease

The aim of this study was to assess whether or not continuous infusion of lisuride in combination with intermittent levodopa-carbidopa administration was associated with tolerance. Intravenous apomorphine was given to four patients before initiation of chronic treatment with subcutaneous lisuride infusion and oral levodopa. The study was repeated under identical conditions after a mean of 18 months of treatment. In no case was the motor response induced by apomorphine infusion reduced as compared to baseline assessment. Choreic dyskinesias accompanying the "on" state were enhanced in all patients. These findings suggest that chronic continuous infusion of a dopamine agonist like lisuride, associated with oral levodopa, is not accompanied by tolerance or down-regulation of striatal dopaminergic receptors.

Stereoselective reversal of MPTP-induced parkinsonism in the marmoset after dermal application of N-0437

The selective dopamine D-2 receptor agonist N-0437 produced a rapid and dose-dependent reversal of motor deficits lasting 90-120 min following i.p. or oral administration of the racemate to MPTP-treated common marmosets. In contrast, topical application of (+/-)-, (+)- or (-)-N-0437 to the skin of MPTP-treated animals did not alter locomotor activity in the initial 4 h although other motor disabilities were reduced. However, 24 h following application of the racemate or the (-) enantiomer both locomotor activity and the other motor deficits induced by MPTP were improved. The increase in locomotor activity returned to basal values by 48-52 h following application of the racemate to the skin and by 72-76 h following administration of (-)-N-0437; the other motor deficits induced by MPTP were reduced for up to 72-76 h by both (+/-)- and (-)-N-0437. Application to skin of the (+) enantiomer produced no behavioural improvement or stimulation of locomotor activity. Transdermal administration of the active enantiomer of N-0437 may be of value in producing a prolonged reversal of parkinsonian motor deficits in man.

One year treatment with lisuride delivery pump in Parkinson's disease

1. A group of 14 fluctuating Parkinsonian patients underwent the subcutaneous Lisuride treatment, administered by an insulin delivery pump. Clinical response has been studied during a one year period. 2. Some patients (8 out of 14) were in combined therapy, assuming a relative small amount of oral L-Dopa together with subcutaneous Lisuride. 3. Lisuride confirmed, also by the subcutaneous route, its antiparkinsonian properties, without any loss of therapeutical efficacy during the 12 month period considered. 4. 7 patients dropped-out from the study, due to psychiatric or systemic side-effects and to "technical" management of the pump. 5. The only 2 patients assuming a 24 hour regimen of Lisuride infusion were among the withdrawn subjects. They were also the only to complain severe psychiatric disturbances.

Comparison of Sinemet CR4 and standard Sinemet: double blind and long-term open trial in parkinsonian patients with fluctuations

"Wearing-off" effect, the most common form of levodopa-induced fluctuations, seems to be related to the short plasma half-life of the drug. More sustained plasma levodopa levels may be achieved with a new controlled-release formulation of carbidopa/levodopa, Sinemet CR4. We studied 20 patients, 12 men and 8 women, with Parkinson's disease complicated by "wearing-off" phenomenon. Mean age was 61.1 +/- 8.1 years, duration of symptoms 8.3 +/- 2.4 years, and the Hoehn-Yahr stage 3.0 +/- 0.9. In a 12-week double-blind study, the average number of tablets administered per day decreased from 5.7 +/- 1.2 to 3.8 +/- 0.7 when Sinemet CR4 (50/200) was substituted for the standard Sinemet (25/100) (p less than 0.001). However, this was at the expense of reducing the "on" time (without dyskinesia) from 9.3 +/- 4.6 to 7.5 +/- 4.3 (p less than 0.05), although the total "on" time did not significantly change. In a long-term follow-up of 18 patients, the "on" time with dyskinesia and morning dystonia significantly increased (p less than 0.05). There was no significant change in the total daily dosage of levodopa, but the daily number of doses and tablets significantly decreased (p less than 0.001). Despite increased dyskinesia, most patients preferred taking fewer tablets and have elected to continue taking Sinemet CR4 instead of standard Sinemet. Sinemet CR4 seems to offer a new and effective strategy for the management of levodopa-related fluctuations.

Subcutaneous apomorphine in parkinsonian on-off oscillations

Subcutaneous apomorphine, a dopamine agonist, was given by continuous infusion during the day or by repeated injections to 19 patients with Parkinson's disease disabled by severe on-off fluctuations. All patients were also given domperidone. The 11 patients treated by infusion showed marked and sustained improvement, and their mean duration of daily off periods over a period of 15 months fell by 6.3 h; similar results were obtained in 8 patients with less severe disabilities who were given repeated apomorphine injections. The therapeutic response to apomorphine was similar to that seen with intravenous levodopa; in patients treated by infusion the mean daily levodopa dose was reduced by 209 mg. These results confirm that during off periods dopamine receptors remain responsive to stimulation and provide evidence of a new, effective, and well-tolerated treatment for the most disabling complication of long-term levodopa therapy.