Subcutaneous apomorphine in Parkinson's disease

Current and novel infusion therapies for patients with Parkinson's disease

Advanced Parkinson's disease is characterized by periods of poor mobility, dyskinesia and progressive decline in functional independence of the affected person despite the manipulation of levodopa doses and the introduction of supplemental therapies such as catechol-O-methyl transferase inhibitors, monoamine oxidase-B inhibitors and dopamine agonists. The implementation of drug delivery systems allows to bypass problems related to irregular and often unpredictable intestinal absorption of oral levodopa, which significantly affects its bioavailability and contributes to the development and persistence of motor complications. Subcutaneous apomorphine and levodopa/carbidopa jejunal infusion systems have been available for many years and their efficacy is confirmed by randomized studies and long-term experience in many centers worldwide. Recently, a new formulation of levodopa/carbidopa infusion gel that includes the catechol-O-methyl transferase inhibitor Entacapone has been introduced to the market. The use of entacapone allows to reduce total daily dose of administered levodopa. Two different soluble formulations of levodopa/carbidopa (ND0612 and ABBV-951) have completed clinical development, and both can ensure subcutaneous delivery by a portable pump infusion system. ABBV-951 uses a foslevodopa/foscarbidopa formulation, both prodrugs to improve absorption and tolerability. Both systems provide effective improvement of motor complications and are likely to expand the therapeutic options in advanced patients. Future efforts should focus on the earlier detection of patients who are candidates for device-aided therapies, increasing appropriate referral and broadening the availability of these treatments globally.

Intermittent Apomorphine Use for off Period Rescue in Parkinson's Disease: A Pragmatic Review of over Three Decades of Clinical Experience

Background

Although proven very efficacious as treatment for Parkinson's disease by Schwab as far back as the 1950s, and later confirmed by Cotzias and colleagues in the early 1970s, use of intermittent subcutaneous injections of the dopamine agonist apomorphine remains limited worldwide.

Objectives

To review evidence regarding use of intermittent, on-demand apomorphine as a treatment for off-period disability in Parkinson's disease.

Methods

A PRISMA-compliant structured literature search was carried out with a focus on clinical effect (motor improvement, daily off time decrease; latency, duration), antiemetic prophylaxis, and adverse events.

Results

Fifty-eight studies were evaluated. Apomorphine administration route was subcutaneous in 29 (50%), sublingual in 14 (24.1%), intranasal in 6 (10.3%), inhaled in 5 (8.6%), rectal in 3 (5.2%) and transdermal in 1 (1.7%). Irrespective of the route, motor disability improved 19% to 74% and daily off time decreased 3% to 68%, with subcutaneous having the fastest onset of action ranging from 6 to 24 minutes and lasting 28 to 96 minutes. Antiemetic prophylaxis was used in almost all studies. Systemic side effects like nausea and yawning were mild and well tolerated, but sedation led to discontinuation of subcutaneous apomorphine in 5.5%. Local side effects to subcutaneous administration did not result in discontinuation. Stomatitis with the early sublingual formulations led to discontinuation in nearly half of patients and was reduced to 16.7% with novel film strips.

Conclusions

Intermittent subcutaneous injections remain the most reliable and safest route of apomorphine administration, with an efficacy for off period treatment supported by nearly four decades of clinical experience.

Novel Dopamine Therapeutics for Cognitive Deficits in Schizophrenia

Schizophrenia is characterized by profound cognitive deficits that are not alleviated by currently available medications. Many of these cognitive deficits involve dysfunction of the newly evolved, dorsolateral prefrontal cortex (dlPFC). The brains of patients with schizophrenia show evidence of dlPFC pyramidal cell dendritic atrophy, likely reductions in cortical dopamine, and possible changes in dopamine D1 receptors (D1R). It has been appreciated for decades that optimal levels of dopamine are essential for dlPFC working memory function, with many beneficial actions arising from D1R stimulation. D1R are concentrated on dendritic spines in the primate dlPFC, where their stimulation produces an inverted-U dose response on dlPFC neuronal firing and cognitive performance during working memory tasks. Research in both academia and the pharmaceutical industry has led to the development of selective D1 agonists, e.g., the first full D1 agonist, dihydrexidine, which at low doses improved working memory in monkeys. Dihydrexidine has begun to be tested in patients with schizophrenia or schizotypal disorder. Initial results are encouraging, but studies are limited by the pharmacokinetics of the drug. These data, however, have spurred efforts toward the discovery and development of improved or novel new compounds, including D1 agonists with better pharmacokinetics, functionally selective D1 ligands, and D1R positive allosteric modulators. One or several of these approaches should allow optimization of the beneficial effects of D1R stimulation in the dlPFC that can be translated into clinical practice.

Apomorphine - pharmacological properties and clinical trials in Parkinson's disease

Apomorphine is often considered an archetypal dopamine agonist used in the treatment of Parkinson's disease (PD). However, it can be clearly differentiated from most other commonly used dopamine agonists on the basis of its pharmacology and on its unique clinical profile. Like levodopa and dopamine, apomorphine acts as a potent, direct and broad spectrum dopamine agonist activating all dopamine receptor subtypes. It also has affinity for serotonin receptors, and α-adrenergic receptors. Apomorphine is usually titrated to a dose that provides an equivalent antiparkinsonian response to that provided by levodopa, and its subcutaneous delivery allows a rapid onset of action, usually within 7-10 min. The mode of apomorphine delivery impacts on its clinical profile so as to provide two very different approaches to therapy in PD. When administered as an acute subcutaneous injection, it induces reliable and rapid relief from OFF periods underscoring its utility as a rescue medication. When given as a subcutaneous infusion, it significantly improves overall daily OFF time and there is also evidence to suggest that, in those patients who replace most or all of their oral drugs with apomorphine infusion, dyskinesia may also improve. In this paper, we review the rich pharmacology of apomorphine and review its efficacy in PD based on data from clinical trials.

Role of apomorphine in the treatment of Parkinson's disease

Current research shows that apomorphine is an effective treatment for symptoms of Parkinson's Disease (PD). The highly lipophilic structure allows apomorphine to cross cell membranes rapidly, leading to the rapid onset of action for on/off symptoms of PD. The use of apomorphine was limited in the past due to peripheral side effects, but with the advent of better delivery systems and medications to control side effects, apomorphine is better tolerated and more widely in use. The major delivery systems are continuous subcutaneous infusions and intermittent subcutaneous injections, but other delivery routes are under investigation. The purpose of this article is to discuss the current use of apomorphine, the current delivery systems and to discuss future research.

[Apomorphine in advanced Parkinson disease]

Apomorphine is the most potent dopamine receptor agonist and its symptomatic effectiveness is comparable to levodopa. Subcutaneous apomorphine is rapidly and completely absorbed. Plasma peak concentrations are achieved after 5-15 minutes and onset of clinical effect is within 20 minutes. Apomorphine intermittent subcutaneous injections are effective as rescue therapy for unpredictable off periods in advanced Parkinson disease (PD). More often apomorphine is administered as a subcutaneous infusion which secures the continuous dopaminergic stimulation. The benefit on 'off' periods is consistent across all studies, but dyskinesia improvement is not so obvious. Two infusion therapies (apomorphine and intraduodenal levodopa) and deep brain stimulation (DBS) are effective in advanced PD patients with untreatable motor complications. Apomorphine infusions should be considered in patients unable to undergo DBS because of cognitive impairment and neurosurgical contraindications.

Enhancing dopamine treatments: worth the effort?

SUMMARY Dopamine-based treatments underlie our current management of the motor symptoms of Parkinson’s disease. In this article, we look at the development of levodopa therapy, combination therapies with levodopa/dopa decarboxylase inhibitors, use of dopamine agonists, monoamine oxidase inhibitors, catechol-O-methyl transferase inhibitors and the development of nonoral delivery methods, in particular in the treatment of motor complications in later PD. There are some shortcomings of dopamine-based therapies including a limited benefit on the non-motor manifestations of Parkinson’s disease. We conclude by looking at the themes for future developments to further enhance dopamine delivery methods.

[Intermittent apomorphine injections as rescue therapy for advanced Parkinson's disease. Consensus statement]

Intermittent subcutaneous apomorphine therapy should be considered in patients with advanced Parkinson's disease who experience recurrent off periods despite optimised oral treatment (according to guidelines), for reliable and quick reversal of these otherwise refractory periods. Such treatment is also called rescue therapy. At present, apomorphine injections with the apomorphine pen are underutilised, considering its current indications and contraindications. In the present consensus statement, concepts for the use of apomorphine are presented and discussed based on existing study results, indications, and contraindications. Recommendations for a practical approach are also provided.

Apomorphine in the treatment of Parkinson's disease

Motor fluctuations, refractory to conventional medical management, are one of the most troubling aspects of Parkinson's disease. Apomorphine is a dopaminergic agent that has been known to the medical community for more than a century, but has only recently been developed to treat such motor fluctuations. In this article, the authors review the historical background, structure, mechanism of action, pharmacologic properties, clinical trials, indications and side effects, as well as avenues of further research, of apomorphine.

L’apomorphine en perfusion sous-cutanée continue dans le traitement de la maladie de Parkinson

Apomorphine administered by subcutaneous infusion has been used efficiently in parkinsonian patients to treat severe motor fluctuations and levodopa-induced dyskinesias. Despite increasing evidence of its efficacy and its relative safety, apomorphine infusion therapy is still underused. This article reviews pharmacokinetic properties, efficacy, tolerability and indications of apomorphine infusion in Parkinson's disease.

Update on Apomorphine for the Rapid Treatment of Hypomobility (“Off”) Episodes in Parkinson's Disease

As Parkinson's disease progresses, fluctuations between akinesia, or hypomobility ("off" times), and mobility ("on" times) increase in frequency despite optimized pharmacotherapy. Motor fluctuations include predictable shortening of therapeutic effects, nocturnal or early morning akinesia, random hypomobility, and delayed mobility (variable responses to individual doses of drugs). Current oral antiparkinson drugs are inadequate for rapid and consistent relief of symptoms during hypomobility. Apomorphine, an injectable dopamine agonist recently introduced in the United States, is indicated for the management of hypomobility associated with advanced Parkinson's disease. Subcutaneous apomorphine is effective for rapid and consistent rescue from hypomobility, with a magnitude of motor improvement similar to that of levodopa. The effect begins within 20 minutes after dosing and lasts approximately 100 minutes. Therapeutic rescue doses are 2-6 mg, and patients typically require approximately three rescue doses/day. Apomorphine is associated with a clinically significant potential to cause nausea and orthostatic hypotension. These potential effects can be managed with antiemetic prophylaxis and appropriate determination of the therapeutic rescue dose.

A review of intermittent subcutaneous apomorphineinjections for the rescue management of motor fluctuations associated with advanced Parkinson's disease

BACKGROUND

As Parkinson's disease (PD) progresses,despite optimized pharmacotherapy, patients experience more frequent fluctuations between symptomatic improvement ("on" times) and the return of motor features ("off" times). Apomorphine, the first injectable dopamine agonist available in the United States, is indicated for the acute treatment of "off" episodes (eg, end-of-dose wearing-off episodes, unpredictable "on/off" episodes) in patients with advanced PD who are receiving medically optimal antiparkinsonian therapy.

OBJECTIVE

This article reviews the pharmacology,clinical efficacy, and tolerability of intermittent subcutaneous apomorphine injections for the management of "off" episodes in patients with PD.

METHODS

MEDLINE (1966-July 2005), the Cochrane Database of Systematic Reviews, and International Pharmaceutical Abstracts (1970-July 2005) were searched for original research and review articles published in English. The search terms were apomorphine and Parkinson's disease. The reference lists of articles were also consulted, as was selected information provided by the manufacturer of apomorphine. All relevant identified studies on intermittent subcutaneous administration of apomorphine were included in the review; trials of continuous subcutaneous infusion and non-subcutaneous administration of apomorphine were excluded.

RESULTS

Intermittent subcutaneous administration of apomorphine produced consistent rescue from "of" episodes in patients with advanced PD, with a symptomatic motor improvement between the predose "off" state and postdose "on" state similar to that achieved with levodopa. The onset of effect occurred within 20 minutes, and the duration of effect was approximately 100 minutes. The therapeutic rescue dose ranged from 2 to 6 mg. During the clinical development program for subcutaneously injected apomorphine, patients required a mean of approximately 3 rescue doses per day. Common adverse effects occurring in > or =20% of patients were injection-site reaction, yawning, dyskinesias, drowsiness, nausea and vomiting, dizziness or postural dizziness, and rhinorrhea.

CONCLUSIONS

The available clinical studies indicate that apomorphine is effective in providing prompt and consistent rescue from "off" episodes in patients with PD. Antiemetic prophylaxis and close medical supervision are recommended when initiating apomorphine therapy.

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.

Apomorphine: an underutilized therapy for Parkinson's disease

Apomorphine was the first dopaminergic drug ever used to treat symptoms of Parkinson's disease. While powerful antiparkinsonian effects had been observed as early as 1951, the potential of treating fluctuating Parkinson's disease by subcutaneous administration of apomorphine has only recently become the subject of systematic study. A number of small scale clinical trials have unequivocally shown that intermittent subcutaneous apomorphine injections produce antiparkinsonian benefit close if not identical to that seen with levodopa and that apomorphine rescue injections can reliably revert off-periods even in patients with complex on-off motor swings. Continuous subcutaneous apomorphine infusions can reduce daily off-time by more than 50% in this group of patients, which appears to be a stronger effect than that generally seen with add-on therapy with oral dopamine agonists or COMT inhibitors. Extended follow-up studies of up to 8 years have demonstrated long-term persistence of apomorphine efficacy. In addition, there is convincing clinical evidence that monotherapy with continuous subcutaneous apomorphine infusions is associated with marked reductions of preexisting levodopa-induced dyskinesias. The main side effects of subcutaneous apomorphine treatment are related to cutaneous tolerability problems, whereas sedation and psychiatric complications play a lesser role. Given the marked degree of efficacy of subcutaneous apomorphine treatment in fluctuating Parkinson's disease, this approach seems to deserve more widespread clinical use.

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.

Median nerve somatosensory evoked potentials. Apomorphine-induced transient potentiation of frontal components in Parkinson's disease and in parkinsonism

Somatosensory evoked potentials (SEPs) to median nerve stimulation have been recorded from parietal and frontal districts in 43 parkinsonians, 17 patients with parkinsonism and 35 healthy controls matched for age and sex. Latency/amplitude characteristics of the parietal P14-N20-P25 and of the frontal P20-N30-P40 wave complexes before and after (10, 20, 30 and 60 min) subcutaneous administration of apomorphine chloride were evaluated in all the 60 patients and in 3 controls. The frontal waves N30 and P40 were either absent or significantly smaller than normal in 31 patients with Parkinson's disease (PD) (72.1%) and in 9 with parkinsonism in baseline records (56.3%). Following apomorphine, the parietal deflections did not significantly vary in amplitude. On the contrary, the frontal complex showed a significant amplitude increase in 27 PD and 8 parkinsonisms (respectively 62.8 and 47.1%); 79.1% of PD and 35.3% of parkinsonisms were improved clinically. Amplitude increase was evident at 10 min after apomorphine, in parallel with clinical improvement, and vanished nearly in coincidence with the end of the clinical effect.

Apomorphine for motor fluctuations and freezing in Parkinson's disease

OBJECTIVE

To review the pharmacokinetics and use of apomorphine in patients with Parkinson's disease; to report a case of beneficial outcome with apomorphine in a patient with Parkinson's disease with severe levodopa "on-off" fluctuations and freezing; and to outline the types of patients or situations where apomorphine may be useful.

DATA SOURCES

Case reports, review articles, and relevant clinical studies identified by a MEDLINE search of the English-language literature published between 1975 and October 1994.

STUDY SELECTION

Because all but 2 reports were of open-label design with small sample sizes, all studies identified were evaluated.

DATA EXTRACTION

The following data were extracted from each study: apomorphine treatment duration, dosing, onset, duration, and adverse effects. The following efficacy variables were extracted: percent decrease in off periods, improvement in parkinsonian symptoms, and percent decrease in levodopa dosage.

DATA SYNTHESIS

Efficacy of apomorphine following subcutaneous, rectal, sublingual, and intranasal dosage forms are evaluated. We also describe the use of apomorphine in a patient with Parkinson's disease who experienced on-off fluctuations and freezing. Based on these reports, recommendations for patient selection, product selection, and apomorphine dosing guidelines are presented.

CONCLUSIONS

Apomorphine decreases off time, freezing, and levodopa requirements in patients with Parkinson's disease. It can be administered via a number of different nonoral routes; however, subcutaneous apomorphine is the most extensively studied. Rectal, sublingual, and intranasal routes also have been shown to provide benefit in motor fluctuations, but differ from the subcutaneous route in onset of action, duration of effect, and adverse effect profile.

Apomorphine infusional therapy in Parkinson's disease: clinical utility and lack of tolerance

We assessed the clinical utility of apomorphine infusional therapy in patients with parkinsonism and motor fluctuations and sought evidence for alterations in drug response resulting from chronic treatment. Six patients with Parkinson's disease were treated for 3 months with s.c. infusions of apomorphine administered during waking hours. At the beginning and the end of the study, test doses of apomorphine (12.5-100 micrograms/kg) were administered to establish a dose-response curve. Over the study, the patients reported a significant improvement in the number of "on" hours experienced per day and substantially reduced the dose and frequency of levodopa and other antiparkinsonian medications. No average change in apomorphine dose-response relationships or pharmacokinetics was observed during the study. However, two patients lowered the infusion rate during the 3-month observation and exhibited higher drug levels and longer responses following test doses of apomorphine given at the end of the study. Although pragmatic concerns with the use of infusion pumps solutions and adverse effects limited the overall benefit afforded by the treatment, this kind of drug treatment may be useful in selected patients with severe parkinsonism and fluctuations.

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.

Comparison of two software programs to be used for the calculation of population pharmacokinetic parameters

The pharmacokinetic parameters of apomorphine, a potent dopamine agonist, were calculated after subcutaneous and intranasal administration. Two available software packages for TDM were used (USC*PACK and MW/PHARM). The findings for the calculated parameters Kel, Vslope, Ka and bioavailability were compared. Although small, sometimes significant differences were found, the NPEM program from the USC*PACK collection provides most information about the population under investigation. We found a median Vslope of 1.7408 +/- 0.8461 (S.D.) 1/kg, and a mean Kel of 1.5341 +/- 0.3748 h-1. The absorption after intranasal administration was extremely rapid: Ka = 20.5 +/- 1.96 h-1, comparable with that found with subcutaneous absorption: Ka = 23.04 +/- 2.20 h-1.

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.

Pharmacokinetics of apomorphine in parkinsonian patients

Apomorphine, a dopamine agonist, has been used efficiently in parkinsonian patients to treat severe levodopa-induced on-off phenomenon. Motor improvement has been obtained both with continuous subcutaneous (SC) infusions, and multiple SC injections. So as to assist in the understanding of the clinical results, we studied the peripheral pharmacokinetics of apomorphine in 20 patients after intravenous (IV) or SC injections in the anterior abdominal wall and in the thigh at various doses, or SC infusion. Plasma apomorphine levels were measured by high-performance liquid chromatography with electrochemical detection. After an SC injection in the abdominal wall, the Tmax was brief (16 +/- 11 min) the drug was rapidly cleared from the plasma and had a short plasma half-life (69.7 +/- 25.8 min). The AUC was similar following SC and IV injections, suggesting that apomorphine was completely absorbed from subcutaneous tissue. Inter-subject variability in drug absorption was large. We noticed a trend towards a more complete absorption following injection in the abdominal wall rather than in the thigh. In patients chronically treated by continuous SC infusion, the apparent plasma half-life was five times longer than that following SC or IV injections. These pharmacokinetic data may explain the rapid onset and brief duration of clinical effects, and the usefulness of individual titration for intermittent SC apomorphine injections, and the smoother motor response obtained with continuous SC infusions.

Apomorphine-induced relief of the akinetic-rigid syndrome and early median nerve somatosensory evoked potentials (SEPs) in Parkinson's disease

Among early cortical median nerve SEPs the frontal N30 potential is known to show amplitude reduction during execution of voluntary movements and to be abnormally reduced in parkinsonian patients. However, it is not clear whether N30 abnormalities are related to the severity of motor disability in Parkinson's disease. To address this question we studied median nerve SEPs, using a 16-channel montage, in 7 patients chronically treated with subcutaneous (s.c.) injections of apomorphine hydrochloride for spontaneous "on-off" motor fluctuations. We observed no significant changes in the latency, amplitude or scalp topography of early SEPs when comparing traces and maps obtained in the "off" condition and during the "on" phase induced by s.c. injection of apomorphine. The absence of any SEP changes, despite a clear-cut relief of the akinetic-rigid syndrome, suggests that early cortical SEPs, and in particular the frontal N30 potential, at least when recorded in a subject at rest, are not usable as an objective means to assess the severity or the fluctuations of motor disability in Parkinson's disease.

Apomorphine test for dopaminergic responsiveness: a dose assessment study

The clinical diagnosis of idiopathic Parkinson's disease (IPD) remains difficult and is supported by a favorable response to levodopa, while failure to respond represents an exclusion criterion. Recently, the response to subcutaneous apomorphine has been suggested as a tool in predicting levodopa responsiveness in parkinsonian syndromes. We administered apomorphine at doses of 10, 50, and 100 micrograms/kg subcutaneously against placebo over two consecutive days in 37 patients with parkinsonism and evaluated the motor response for 90 min after each dose. Subsequently, we compared the motor response with the follow-up response to levodopa therapy and to a final diagnosis. Twenty-seven patients of 37 showed a positive response to apomorphine, and 10 had a negative response. All positive responses to the apomorphine test were obtained with 50 or 100 micrograms/kg doses. Because of the high frequency of side effects with the dose of 100 micrograms/kg, 50 micrograms/kg seems more useful. After an adequate period of levodopa/carbidopa therapy (12-month follow-up), 29 patients improved; 25 of these had demonstrated a positive response to the apomorphine test. The final diagnosis of IPD, made on the basis of an exhaustive clinical and neuroradiological evaluation and on the response to chronic levodopa therapy, was in good agreement with the response to the apomorphine test (predictivity of diagnosis, 86.4%). Our data indicate that subcutaneous apomorphine at the dose of 50 micrograms/kg is a useful tool in the differential diagnosis of parkinsonian syndromes.

Subcutaneous apomorphine in Parkinson's disease: response to chronic administration for up to five years

Subcutaneous apomorphine, administered by continuous waking-day infusion with boluses, or by repeated intermittent injection, was given to 71 parkinsonian patients with severe refractory levodopa related on-off fluctuations for 1-5 years. A mean reduction in daily off period time of approximately 50% was maintained, and the incidence of neuropsychiatric toxicity remained low on long-term follow-up. No clinically significant tolerance or loss of therapeutic effect was seen, although increasingly severe on-phase dyskinesias and postural instability marred the long-term therapeutic response in many patients. Despite these drawbacks, apomorphine, when combined with the peripheral dopamine receptor agonist domperidone, represents a significant therapeutic advance in the management of late-stage Parkinson's disease and should certainly be considered before experimental implantation procedures.

Dopamine agonists in Parkinson's disease: a look at apomorphine

Apomorphine is a D1 and D2 dopamine receptor agonist with anti-parkinsonian properties qualitatively similar to those seen with L-dopa. It was first used in the treatment of Parkinson's disease by Schwab in the 1950s but owing to its short duration of action, the need for parenteral administration, and adverse reactions including nausea, vomiting, postural hypotension and sedation, it was not widely prescribed. In the early 1970s, Cotzias confirmed its potent anti-parkinsonian effects and that some of its secondary effects were diametrically opposite to those seen with L-dopa. The advent of peripheral dopamine receptor antagonist drugs, which counteract the unwanted effects of apomorphine, and the development of new drug delivery systems including insulin pens and ambulatory mini pumps have led to the resurrection of apomorphine for the treatment of Parkinson's disease. Over the last five years in Europe, the drug has proved to be a major advance in the treatment of refractory "on-off" oscillations in Parkinson's disease. It has also been used as a diagnostic test for dopaminergic responsiveness in Parkinson syndromes and tremors of uncertain aetiology. The drug has also proved particularly useful in dealing with certain "off-period" disabilities, including pain, bladder dysfunction, dystonia and gastro-intestinal symptoms. Continuous steady state infusion of apomorphine by mini-pump may reduce the severity of "on" phase dyskinesias over time. The drug has also proved useful in the clinical pharmacological investigation of the pathophysiology of the motor response to dopaminergic drugs in Parkinson's disease and the occurrence of involuntary movement sequences. Neuropsychiatric side-effects are relatively infrequent when compared with ergolene dopamine agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Apomorphine in treatment of Parkinson's disease: comparison between subcutaneous and sublingual routes

The efficacy of two routes of apomorphine, subcutaneous (SC) and sublingual (SL), successively administered in 7 Parkinsonian patients with motor fluctuations, was compared in reducing the daily duration of "off" phases. The mean duration of SC and SL treatment was 7.7 and 6.8 months respectively. The mean time spent in "off" phase was 55% after SC and 68% after SL treatment. The mean time before turning "on" after an "off" period was 14 minutes after SC and 28 minutes after SL treatment. Two patients developed stomatitis after SL route. SL apomorphine may be helpful in the treatment of motor fluctuations in PD.

Behavioral tolerance to repeated apomorphine administration in parkinsonian monkeys

Four consecutive injections (s.c.) of apomorphine (Apo) were given to 5 parkinsonian monkeys after i.v. MPTP administration. The minimal effective dose (MED) of Apo was defined as that capable of reducing motor disability by 50% or more for a minimum period of 30 min. Repeated apomorphine injections were given with an interval of 30 min after the motor effect of the previous injection had worn off or with a separation of 3 h between injections. The doses used in different experiments were the MED (2.4 micrograms/kg), 4 MED and 8 MED. In every experiment the duration of motor benefit was longest with the first Apo injection. There was a decay in the duration of the response elicited by consecutive Apo injections when given 30 min after the previous effect had waned. This was significant for the MED and 4 MED (ANOVA, P < 0.01). When Apo boluses were given with an interval of 3 h there was a significant reduction in the duration of the response elicited by the MED, 4 MED and 8 MED of apomorphine. For the MED the reduction in the duration of the motor response was significantly greater for injections given with a 30-min interval than 3-h interval. These findings indicate that behavioral hyposensitivity to repeated Apo administration in parkinsonian monkeys occurs preferentially when near threshold doses are given with short intervals.

The clinical use of apomorphine in Parkinson's disease

Our 2-year experience in the therapeutic use of subcutaneous apomorphine has involved 25 patients with Parkinson's disease, 10 of whom continue to use it chronically. On the basis of this experience, we have formulated certain indications for its use, together with suggested approaches to modify patients' oral drug regimes so that apomorphine can best be deployed to improve their quality of life.

Sublingual apomorphine solution in Parkinson's disease

OBJECTIVE

To compare the effects of single doses of oral levodopa, subcutaneous apomorphine and sublingual apomorphine.

DESIGN

Single-blind placebo-controlled comparative study.

SETTING

Subjects were admitted as day patients to the neurology ward.

PATIENTS

Five patients with idiopathic Parkinson's disease and "end of dose deterioration" entered and completed the study.

INTERVENTIONS

Patients were given domperidone (20 mg by mouth three times a day) to prevent nausea and apomorphine (1-3 mg by subcutaneous injection), apomorphine in glycerol (10-30 mg sublingually) or their usual levodopa regimen.

MAIN OUTCOME MEASURES

Efficacy, time to onset of effect and duration of effect of oral levodopa, subcutaneous apomorphine and sublingual apomorphine. Tremor amplitude and timed pegboard and gait tasks were used as objective indices of clinical state.

RESULTS

Maximal efficacy of the three treatments was comparable (P = 0.28-0.99). Mean latency to onset of effect of both formulations of apomorphine was less than that of levodopa (P = 0.022-0.048) but so was the duration of effect (P = 0.044-0.049).

CONCLUSIONS

Sublingual apomorphine may be a convenient means of rapidly terminating "off" periods associated with long term levodopa therapy.

Intermittent subcutaneous apomorphine injection treatment for parkinsonian motor oscillations

Eight patients with severe Parkinsonian motor oscillations have been treated with the dopamine receptor agonist apomorphine by intermittent subcutaneous self-injection as an adjunct to oral anti-Parkinsonian medication. The dopamine receptor antagonist domperidone was also given by mouth to prevent nausea. Six patients remain on chronic treatment (mean period 6.5 months) with improved control of motor function in each case. Four have had major enhancement of their quality of life. Benefits of this treatment stem from the training of patients to use intelligent behaviour to administer a promptly acting and effective pharmacological agent, thereby exercising a degree of direct control over previously unpredictable variations in motor performance.

Absorption of apomorphine by various routes in parkinsonism

We wanted to determine the absorption and clinical effect of sublingual (SL) and transdermal apomorphine in parkinsonism. Patients received single SL apomorphine doses (N = 7) and the absorption was compared with parenteral (N = 5) and oral (N = 4) doses. One patient received a transdermal dose of apomorphine. The relative bioavailability of SL apomorphine ranged from 10 to 22% of a parenteral apomorphine dose. Oral apomorphine was less than 4% bioavailable, and the transdermal dose did not produce detectable plasma levels. Three patients with motor fluctuations responded to SL apomorphine, with a latency to effect of 20-40 min and a duration of effect of 15-100 min. One patient used SL apomorphine as an adjunct with levodopa, and during 1 month reported a large decrease in "off" periods. We conclude that apomorphine is effectively absorbed by the sublingual route.

Relation between plasma concentration and clinical efficacy after sublingual single dose apomorphine in Parkinson's disease

Five patients with Parkinson's disease were given a single sublingual dose of apomorphine in 3 mg tablets (2 patients received 18 mg and 3 patients took 39 mg). The therapeutic effect appeared within 33.0 min and lasted 137 min. There was a significant correlation between peak concentration, area under the curve, dose (mg/kg) and the duration of the therapeutic effect.

Comparison of motor response to apomorphine and levodopa in Parkinson's disease

The magnitude and pattern of motor responses to single doses of subcutaneous apomorphine and oral levodopa were compared in 14 patients with Parkinson's disease. Although apomorphine produced much shorter motor responses than levodopa, the quality of response to the two drugs was virtually indistinguishable. These clinical observations support the notion that integrity of striatal post-synaptic dopamine receptors is a key determinant of responsiveness to dopaminergic treatment in Parkinson's disease.