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

Efficacy and safety of apomorphine pump infusion in Filipino patients insufficiently controlled on oral anti-Parkinson medications: an open-label, pilot study

BACKGROUND

Apomorphine hydrochloride is used in the management of advanced Parkinson disease (PD), either as a rescue medication for off periods during levodopa therapy or as a maintenance pump medication. This is the first study to describe the effects of apomorphine in Filipino patients with PD.

OBJECTIVE

To evaluate the safety and efficacy of apomorphine ampules (APO-go®) pump infusion in the treatment of motor fluctuations in patients inadequately controlled on oral anti-Parkinson medications.

METHODS

Patients diagnosed with PD who developed motor fluctuations with levodopa were evaluated at baseline and at the end of the study using the Modified Hoehn and Yahr (H&Y) Scale, the Unified Parkinson's Disease Rating Scale (UPDRS) and the Abnormal Involuntary Movement Scale (AIMS). After initial assessment, patients were administered 20 ampules of apomorphine hydrochloride 10 mg/mL by infusion pump over 20 days. Intention-to-treat (ITT) analysis included all patients who completed at least one posttreatment assessment. Motor disability based on modified H&Y scores, motor function and complications of therapy pre- and posttreatment were compared using Wilcoxon Signed Rank test. Chi-squared test was used to compare outcomes by age and sex. Frequencies of adverse reactions were recorded to evaluate the tolerability of the medication.

RESULTS

Ten patients (mean age 63 ± 9.7 years), 3 male and 7 female, were enrolled in the study. Patients were given apomorphine for at most 16 days. The doses used were 2.5 mg/0.50 mL (n = 2), 3 mg/0.60 mL (n = 6), 4 mg/0.80 mL (n = 1) and 7 mg/1.40 mL (n = 1). After obtaining the threshold dose, two patients discontinued treatment. Eight of nine patients showed significant improvement in H&Y scores after treatment (p < 0.017). There was marked improvement after 10 days of treatment in at least five of 10 patients in terms of motor function using UPDRS, which included tremor (p < 0.034), rigidity (p < 0.002), facial expression (p < 0.014), finger taps (p < 0.008), foot taps (p < 0.014) and gait (p < 0.006). Significant changes from pre- to posttreatment scores in the frequency of dyskinesias (p < 0.010) and dystonia (p < 0.025) were observed. Nine focus areas of AIMS showed significant improvements in the muscles of facial expression (p < 0.020), upper (p < 0.016) and lower extremities (p < 0.010), incapacitation by abnormal movement (p < 0.010) and patients' awareness of abnormal movements (p < 0.039). Six patients experienced adverse events, none of which were related to the study drug.

CONCLUSION

Apomorphine hydrochloride pump infusion therapy is potentially effective and safe in the treatment of motor fluctuations in Filipino patients with PD. This pilot study springboards safe engagements of Filipino PD patients in multicenter, large-scale trials.

Continuous Subcutaneous Infusion Delivery of Apomorphine in Parkinson's Disease: A Systematic Review

Background

Continuous subcutaneous apomorphine infusion (CSAI) is one of the advanced therapies for Parkinson's disease (PD).

Methods

A systematic review of all published articles in English on CSAI for PD till January 30, 2022 was conducted.

Results

A total of 82 articles met the search criteria. Publications included retrospective or prospective open-label observational studies, with a limited number of randomized control trials (RCT). Publications were highly heterogeneous and focused on different aspects of CSAI and included clinical audits, effects on cognition/behavior, axial symptoms, nocturnal issues, adverse events/reasons for discontinuation and comparison with other continuous dopaminergic therapies. CSAI was used in patients who presented severe motor fluctuations not resolved by oral therapy, poor candidates for deep brain stimulation (DBS) due to cognitive/behavioral issues or in those with DBS weaning effect. Recent studies have also shown that CSAI was useful for nocturnal usage in advanced PD, in addition to daytime utilization. Adverse effects were common and include skin lesions, sedation and nausea. Pump management difficulties and patient decisions were common reasons for therapy dropout, predominantly during the initial stages of the CSAI.

Conclusion

There is consistent agreement on the benefits of CSAI in reducing OFF periods and improving ON periods without troublesome dyskinesia and specific motor and non-motor symptoms. Although there is a paucity of RCTs, current data from almost 30 years of use suggests CSAI to be beneficial in advanced cases of PD.

Dose Optimization of Apomorphine Sublingual Film for OFF Episodes in Parkinson's Disease: Is the Prophylactic Use of an Antiemetic Necessary?

BACKGROUND

Nausea is common upon initiating dopamine agonists in patients with Parkinson's disease (PD); however, pretreatment with an antiemetic is recommended only when initiating apomorphine formulations.

OBJECTIVE

Evaluate the need for prophylactic antiemetic use during dose optimization of apomorphine sublingual film (SL-APO).

METHODS

A post hoc analysis of a Phase III study evaluated nausea and vomiting treatment-emergent adverse events in patients with PD who underwent SL-APO dose optimization (10-35 mg; 5-mg increments) to achieve a tolerable FULL ON. Frequencies of nausea and vomiting were described for patients who did versus did not use an antiemetic during dose optimization and by patient subgroups based on extrinsic and intrinsic factors.

RESULTS

Overall, 43.7% (196/449) of patients did not use an antiemetic during dose optimization; most of these patients (86.2% [169/196]) achieved an effective and tolerable SL-APO dose. In patients who did not use an antiemetic, nausea (12.2% [24/196]) and vomiting (0.5% [1/196]) were uncommon. An antiemetic was used in 56.3% (253/449) of patients, with 17.0% (43/253) and 2.4% (6/253) experiencing nausea and vomiting, respectively. All events of nausea (14.9% [67/449]) and vomiting (1.6% [7/449]) were of mild-to-moderate severity except for 1 event each. Irrespective of antiemetic use, among patients without baseline dopamine agonist use, nausea and vomiting rates were 25.2% (40/159) and 3.8% (6/159); in those already using dopamine agonists, rates were 9.3% (27/290) and 0.3% (1/290).

CONCLUSION

Prophylactic treatment with an antiemetic is not necessary for most patients who initiate SL-APO for the treatment of OFF episodes in PD.

Why do 'OFF' periods still occur during continuous drug delivery in Parkinson's disease?

Continuous drug delivery (CDD) is used in moderately advanced and late-stage Parkinson’s disease (PD) to control motor and non-motor fluctuations (‘OFF’ periods). Transdermal rotigotine is indicated for early fluctuations, while subcutaneous apomorphine infusion and levodopa-carbidopa intestinal gel are utilised in advanced PD. All three strategies are considered examples of continuous dopaminergic stimulation achieved through CDD. A central premise of the CDD is to achieve stable control of the parkinsonian motor and non-motor states and avoid emergence of ‘OFF’ periods. However, data suggest that despite their efficacy in reducing the number and duration of ‘OFF’ periods, these strategies still do not prevent ‘OFF’ periods in the middle to late stages of PD, thus contradicting the widely held concepts of continuous drug delivery and continuous dopaminergic stimulation. Why these emergent ‘OFF’ periods still occur is unknown. In this review, we analyse the potential reasons for their persistence. The contribution of drug- and device-related involvement, and the problems related to site-specific drug delivery are analysed. We propose that changes in dopaminergic and non-dopaminergic mechanisms in the basal ganglia might render these persistent ‘OFF’ periods unresponsive to dopaminergic therapy delivered via CDD.

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.

Expert Consensus Group report on the use of apomorphine in the treatment of Parkinson's disease--Clinical practice recommendations

Extensive published evidence supports the use of subcutaneously-administered apomorphine as an effective therapy for Parkinson's disease (PD) but to date no consensus recommendations have been available to guide healthcare professionals in the optimal application of apomorphine therapy in clinical practice. This document outlines best-practice recommendations for selecting appropriate candidates for apomorphine intermittent injection (the pen-injection formulation) or apomorphine continuous infusion (the pump formulation), for initiating patients onto therapy and for managing their ongoing treatment. Apomorphine is a suitable therapeutic option for PD patients who experience troublesome 'off' periods despite optimized treatment with oral PD medications. Due to its speed of onset, apomorphine injection is particularly suited to those patients requiring rapid, reliable relief of both unpredictable and predictable 'off' periods, those who require reliable and fast relief when anticipating an 'off', those with levodopa absorption or gastric emptying problems resulting in delayed or failed 'on', or for rapid relief of early morning dystonia or akinesia. Apomorphine infusion(1) is suited for patients whose 'off' periods can no longer be adequately controlled by standard oral PD treatment or for those in whom rescue doses of apomorphine injection are effective but either needed too frequently (more than 4-6 times per day), or are associated with increasing dyskinesia. In addition to treating motor fluctuations, there is evidence that apomorphine infusion may be effective for the management of specific non-motor symptoms of PD associated with 'off' periods. Apomorphine infusion is less invasive than other non-oral treatment options for advancing disease, intrajejunal levodopa infusion and deep-brain stimulation.

Cost-effectiveness of continuous subcutaneous apomorphine in the treatment of Parkinson's disease in the UK and Germany

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease, affecting ∼ 5.2 million people worldwide. Continuous subcutaneous apomorphine (CSAI) represents an alternative treatment option for advanced PD with motor fluctuation. The purpose of this analysis was to estimate the cost-effectiveness of CSAI compared with Levodopa/carbidopa intestinal gel (LCIG), Deep-Brain-Stimulation (DBS) and Standard-of-care (SOC).

METHODS

A multi-country Markov-Model to simulate the long-term consequences, disease progression (Hoehn & Yahr stages 3-5, percentage of waking-time in the OFF-state), complications, and adverse events was developed. Monte-Carlo simulation accounted for uncertainty. Probabilities were derived from RCT and open-label studies. Costs were estimated from the UK and German healthcare provider's perspective. QALYs, life-years (LYs), and costs were projected over a life-time horizon.

RESULTS

UK lifetime costs associated with CSAI amounts to £78,251.49 and generates 2.85 QALYs and 6.28 LYs (€104,500.08, 2.92 QALYs and 6.49 LYs for Germany). Costs associated with LCIG are £130,011.34, achieves 3.06 QALYs and 6.93 LYs (€175,004.43, 3.18 QALYs and 7.18 LYs for Germany). The incremental-cost per QALY gained (ICER) was £244,684.69 (€272,914.58). Costs for DBS are £87,730.22, associated with 2.75 QALYs and 6.38 LYs (€105,737.08, 2.85 QALYs and 6.61 LYs for Germany). CSAI dominates DBS. SOC associated UK costs are £76,793.49; 2.62 QALYs and 5.76 LYs were reached (€90,011.91, 2.73 QALYs and 6 LYs for Germany).

CONCLUSIONS

From a health economic perspective, CSAI is a cost-effective therapy and could be seen as an alternative treatment to LCIG or DBS for patients with advanced PD.

Clinical insights into use of apomorphine in Parkinson's disease: tools for clinicians

SUMMARY 

Apomorphine was introduced before the era of levodopa as a treatment for idiopathic Parkinson's disease (iPD). A number of practical obstacles were to be solved before a wider use of the drug was possible. Today, however, the drug is probably still underutilized. Apomorphine is a strong nonergoline D1 and D2 receptor agonist with a dopaminergic effect comparable with levodopa. In this review motor and non-motor indications for intermittent injections and subcutaneous apomorphine infusions are listed. The reduction of 'off' periods is more than 50% on infusion therapy and if monotherapy is achieved a significant reduction of pre-existing levodopainduced dyskinesias is seen. The aim of this review is to give practical insight into apomorphine treatment, highlighting side effects, and complications and device-related problems are discussed with advice on how to prevent or handle these, should they occur. A number of practical points including the apomorphine test, requirements of the clinical setting, how to increase adherence and troubleshooting are added.

Drug treatment of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease. While its cause remains elusive, much progress has been made regarding its treatment. Available drugs have a good symptomatic effect, but none has yet been shown to slow the progression of the disease in humans. The most efficacious drug is levodopa, but it remains unclear whether the symptomatic benefit is associated with neurotoxic effects and long-term deterioration. The long-term problem associated with levodopa is the appearance of dyskinesias, which is significantly delayed among patients treated with dopamine agonists as initial therapy. Less clear is the role of other drugs in PD, such as monoamine oxidase inhibitors (MAOIs), including selegiline and rasagiline, the putative N-meihyl-o-aspartaie (NMDA) receptor antagonists amantadine and memantine, and the muscarinic receptor blockers. All these may be used as initial therapy and delay the use of dopaminergic drugs, or can be added later to reduce specific symptoms (tremor or dyskinesias). Advanced PD is frequently associated with cognitive decline. To some extent, this can be helped by treatment with cholinesterase inhibitors such as rivastigmine. Similarly, hallucinations and delusions affect PD patients in the advanced stages of their disease. The use of classical neuroleptic drugs in these patients is contraindicated because of their extrapyramidal effects, but atypical drugs, and particularly clozapine, are very helpful. The big void in the therapy of PD lies in the more advanced stages. Several motor symptoms, like postural instability, dysphagia, and dysphonia, as well as dyskinesias, are poorly controlled by existing drugs. New therapies should also be developed against autonomic symptoms, particularly constipation.

Evaluation and management of the non-motor features of Parkinson's disease

Parkinson's disease (PD) is traditionally viewed as a motor disorder with a characteristic triad of tremor, rigidity and bradykinesia. There is now increasing awareness that PD is a complex systemic disorder with many nonmotor symptoms (NMS) which include autonomic dysfunction, sleep disorders, sensory and neuropsychiatric features. NMS become more common in severity and frequency with advancing disease when neuropsychiatric features such as cognitive impairment and psychosis dominate the clinical picture. NMS are strongly correlated with quality of life for patients and their families as well as institutional care placement. Despite their importance, NMS are poorly recognized by clinicians and often undeclared by patients. Use of a validated screening tool NMSQuest followed by specific symptom assessment instruments strengthens the recognition and holistic management of NMS in PD. Some NMS such as mood disturbance, anxiety, pain and insomnia may be improved by optimization of dopaminergic therapy. Conversely, psychosis, excess daytime somnolence or impulse control disorder (ICD) may be triggered by dopaminergic drugs. Other NMS such as dementia and severe depression may be unresponsive to dopaminergic treatment and may reflect perturbations in cholinergic, serotonergic or noradrenergic neurotransmitter function. These symptoms are more challenging to manage but may be ameliorated to some extent by agents such as acetylcholinesterase inhibitor or antidepressant drugs. This contribution reviews the evidence for the evaluation and management of key NMS in PD (apathy, anxiety, depression, psychosis, dementia, ICD, sleep disturbance, autonomic dysfunction, pain) and highlights the urgent need for both novel therapies and more controlled trials for current therapeutic strategies.

Pharmacokinetics of a once-daily extended-release formulation of pramipexole in healthy male volunteers: three studies

BACKGROUND

Pramipexole is a dopamine agonist used in the treatment of Parkinson's disease. The currently available immediate-release (IR) formulation is taken orally 3 times daily.

OBJECTIVES

These studies were conducted to evaluate the pharmacokinetic properties of a variety of prototypes for a once-daily extended-release (ER) formulation of pramipexole and to further characterize the prototype whose pharmacokinetics best matched those of the IR formulation.

METHODS

Three Phase I studies were conducted, all in healthy adult men aged <or=50 years with a body mass index of 18.5 to 29.9 kg/m(2). In the first study, 7 prototypes of a once-daily ER formulation with various release properties, including rate and pH dependence, were compared with the IR formulation taken 3 times daily to identify the optimal pharmacokinetic resemblance based on predefined criteria derived from plasma AUC(0-24h), C(max), and C(min). In the second study, a level A in vitro/in vivo correlation (IVIVC) suitable for predicting an entire in vivo bioavailability time course based on in vitro dissolution was established and validated, and the single-dose pharmacokinetics of the optimal ER formulation identified in the first study were analyzed for food effect. In the third study, steady-state pharmacokinetics of the optimal ER formulation were assessed across a range of pramipexole doses (0.375-4.5 mg/d), including investigation of the food effect at steady state for the highest dose. Tolerability was assessed throughout all studies based on physical examinations, laboratory measurements, and adverse events (AEs).

RESULTS

The 3 studies included 18, 15, and 39 subjects, respectively. Among the ER prototypes tested at 0.75 mg once daily in study 1, a matrix tablet had the optimal pharmacokinetic resemblance to IR pramipexole 0.25 mg TID, with a geometric mean AUC(0-24h,ss) of 17.4 ng.h/mL (vs 16.0 ng.h/mL for the IR formulation), C(max,ss) of 0.967 ng/mL (vs 1.09 ng/mL), and C(min,ss) of 0.455 ng/mL (vs 0.383 ng/mL). For single-dose ER 0.375 mg administered in the fasted state in study 2, in vivo bioavailability was predictable from in vitro dissolution data, with internal mean absolute percent prediction errors of 3.18% for AUC(0-30h) and 4.87% for C(max), and external mean absolute prediction errors of 6.61% and 3.34%, respectively, satisfying current guidelines for a level A IVIVC. For single-dose ER 0.375 mg administered in the fed state, the upper bound of the 90% CI for fed:fasted values was 119.8 for AUC(0-30h) (within the bioequivalence limits of 80%-125%) and 134.1 for C(max). At steady state in study 3 (subjects' 5th treatment day), dosing at 0.375 to 4.5 mg in the fasted state was associated with a linear, dose-proportional increase in pharmacokinetic parameters, including AUC(0-24h,ss) and C(max,ss). At the highest fasted dose (4.5 mg), the geometric coefficient of variation for interindividual variability at steady state was 30.1% for AUC(0-24h,ss) (vs 21.4% for IR pramipexole 1.5 mg TID) and 22.3% for C(max,ss) (vs 19.0%). At steady state, the upper bounds of the 90% CIs for fed:fasted values with ER 4.5 mg were 122.1 for AUC(0-24h) and 126.8 for C(max). No serious AEs occurred, and the dropout rate was low.

CONCLUSIONS

In these studies in healthy male volunteers, an ER pramipexole formulation was identified that resembled the IR formulation in terms of both pharmacokinetics and tolerability. In patients with Parkinson's disease, once-daily use of an ER formulation may improve the convenience of treatment relative to the IR formulation taken 3 times daily and thus increase compliance.

Apomorphine nodules in Parkinson's disease: best practice considerations

Apomorphine hydrochloride infusion therapy is used by approximately 1000 people with advanced Parkinson's disease in the UK (Britannia Pharmaceuticals Ltd, 2008). Subcutaneous nodules that develop as a result of these infusions can cause discomfort and may impact on the effectiveness of the drug therapy. Community nursing teams have a key role in supporting patients on apomorphine; they may be responsible for administering the drug, or supporting and empowering the patient or their carer to administer the infusion. A recent randomized controlled pilot study by a research group at the University of Hertfordshire investigated the use of therapeutic ultrasound for the treatment of apomorphine nodules. A number of observations about apomorphine nodules and the technique used to site infusions were made which may help to promote safe and effective management of apomorphine therapy. This article is a collaboration between one of the researchers and a Parkinson's disease nurse specialist from the University College of London Hospitals NHS Foundation Trust. It draws on best practice observations from both research and clinical experience and puts them in context of published research. It summarizes best practice considerations for administering infusions, identifies the current treatment and management options that participants from the trial reported using on their nodules, emphasizes the need for standardized documentation and suggests a rating system that may be useful to document nodule severity.

Continuous dopaminergic stimulation: Is it the answer to the motor complications of Levodopa?

Continuous dopaminergic stimulation (CDS) is a treatment strategy hypothesized to avoid or reduce the motor complications of long-term levodopa therapy, motor fluctuations, and dyskinesia, by preventing or reversing sensitization induced by pulsatile dopaminergic stimulation. The CDS hypothesis is itself based on several hypotheses. First, tonic dopaminergic stimulation is physiological. Second, sensitization is undesirable and should be reversed. Third, reduction of off time and dyskinesia can be induced simultaneously. Finally, clinical studies substantiate the CDS hypothesis. The evidence for these hypotheses is reviewed, and the need for randomized clinical trials that rigorously test the CDS hypothesis is emphasized.

Drug Insight: continuous dopaminergic stimulation in the treatment of Parkinson's disease

Continuous dopaminergic stimulation is a therapeutic strategy for the management of Parkinson's disease, which proposes that dopaminergic agents that provide continuous stimulation of striatal dopamine receptors will delay or prevent the onset of levodopa-related motor complications. Dopaminergic neurons in the basal ganglia normally fire in a random but continuous manner, so that striatal dopamine concentrations are maintained at a relatively constant level. In the dopamine-depleted state, however, intermittent oral doses of levodopa induce discontinuous stimulation of striatal dopamine receptors. This pulsatile stimulation leads to molecular and physiologic changes in basal ganglia neurons and the development of motor complications. These effects are reduced or avoided when dopaminergic therapies are delivered in a more continuous and physiologic manner. Studies in primate models and patients with Parkinson's disease have shown that continuous or long-acting dopaminergic agents are associated with a decreased risk of motor complications compared with short-acting dopamine agonists or levodopa formulations. Continuous dopaminergic stimulation can be achieved with a continuous infusion, but infusion therapies are cumbersome and not likely to be acceptable to patients with early disease. The current challenge is to develop a long-acting oral formulation of levodopa that provides comparable anti-parkinsonian benefits without motor complications.

Apomorphin bei der Behandlung des Morbus Parkinson

Apomorphine has long been used in many medical specialties. It is a highly potent D2-, D3- and D4-dopamine receptor agonist with a particularly high D1-dopamine receptor affinity. Due to its almost complete inactivation during liver passage it is usually applied subcutaneously. After rapid onset its effect is waning after about one hour. Apomorphine's action is not dependent on enteral dopamine resorption and on praesynaptic dopamine storage and dopamine secretion mechanisms. When applied subcutaneously its most common side effect is cutaneous nodules at the injection sites. Peripheral dopaminergic side effects, such as nausea and orthostatic hypotension, usually occur only during therapy initiation and respond well to domperidone. Hallucinations occur less frequently than with other dopamine receptor agonists. The apomorphine test determines the levodopasensitivity of a parkinsonian syndrome by application of an apomorphine bolus to distinguish between idiopathic Parkinson's disease and atypical parkinsonian syndromes. It indicates a levodopasensitivity in about 90% of the patients tested. False-negative results can occur in mild parkinsonian syndromes. A meta analysis indicates that intermittent subutaneous apomorphine applications (intermittent apomorphine therapy) with a self application device can reduce the daily duration of unpredictable off-phases by 48.8+/-8.7%. For this an average of 3.7+/-1.1 x 2.9+/-0.8 mg apomorphine has to be applied per day. Continuous subcutaneous apomorphine application with an extracorporal pump (continuous apomorhine therapy) during the wake phase reduces the duration of daily off-phases by 64.8+/-13.5% and the additional levodopa dose by 30.3+/-31.1%. 24-hour application reduces the daily duration of the off-phases by 63.5+/-19.1% and the additional levodopa dose by 65.5+/-21.9%. Levodopa-induced dyskinesias are also substantially reduced. A gradual conversion to an apomorphine monotherapy is possible. Even after prolonged treatment times no significant loss of efficacy occurs. With this profile apomorphine is a highly successful treatment option for off-phases and levodopa-induced dyskinesias in advanced cases of idiopathic Parkinson's disease which should be used before more invasive approaches are considered.

The perioperative management of Parkinson's disease revisited

The perioperative management of patients who have PD requires knowledge of the potential complications of various types of surgery. Neurologists should be able to balance patient comfort against the potential complications of antiparkinsonian therapy. The authors believe that the approach outlined in the Appendix increases patient comfort, facilitates nursing care, and can potentially reduce some of the complications seen in the postoperative period.

Subcutaneous Apomorphine

Apomorphine, a short-acting dopamine D1 and D2 receptor agonist, was the first dopamine receptor agonist used to treat Parkinson's disease. Subcutaneous apomorphine is currently used for the management of sudden, unexpected and refractory levodopa-induced 'off' states in fluctuating Parkinson's disease either as intermittent rescue injections or continuous infusions. Other indications include the challenge test for determining the dopaminergic responsiveness and finding the appropriate dose of the drug in intermittent subcutaneous administration. Except for a rapid on- and offset of the antiparkinsonian response with subcutaneous apomorphine, the magnitude and pattern of the motor response to single dose of subcutaneously administered apomorphine is qualitatively comparable to that of oral levodopa. Seventy-five percent of patients achieve a clinically significant improvement with a dose of apomorphine 4mg. The efficacy of intermittent subcutaneous apomorphine injections as an add-on to levodopa therapy in advanced Parkinson's disease was explored in one short-term, randomised, double-blind, placebo-controlled trial, one short-term and six long-term, open-label, uncontrolled studies, including a total of 195 patients. These studies provide evidence that this mode of administration was successful in aborting 'off' periods and improving Parkinson's disease motor scores, but tended to increase dyskinesias. No levodopa-sparing effect was observed. Eleven long-term, open-label, uncontrolled studies, including a total of 233 patients evaluated the efficacy of continuous subcutaneous apomorphine infusions in monotherapy or as an add-on to levodopa therapy in advanced Parkinson's disease. These studies proved that subcutaneous apomorphine infusions are successful in aborting 'off' periods, reducing dyskinesias and improving Parkinson's disease motor scores with the added benefit of a substantial levodopa-sparing effect. The apomorphine challenge test has at least 80% overall predictive ability to clinically diagnose Parkinson's disease across the different stages of the disease and parkinsonian syndromes. Similarly, those data also indicate that the apomorphine challenge test has a >80% ability to predict dopaminergic responsiveness across all stages of Parkinson's disease. Adverse events are usually mild and consist predominantly of cutaneous reactions and neuropsychiatric adverse effects. The incidence of adverse effects is higher in patients receiving continuous infusion than in those receiving intermittent pulsatile administration. Based on the results of these studies it is recommended that subcutaneous apomorphine either as intermittent injections or continuous infusions should be offered to any suitable Parkinson's disease patient who has difficulties in his/her management with conventional therapy. Low-dose levodopa therapy in combination with waking-day hours subcutaneous apomorphine infusion would probably be the most efficient treatment. Continuous subcutaneous apomorphine infusions should be evaluated before more invasive measures or neurosurgical interventions are contemplated.

Apomorphine infusion and the long-duration response to levodopa in advanced Parkinson's disease

The authors investigated the long-duration response to levodopa in advanced Parkinson's disease. Eight patients with advanced Parkinson's disease disabled by severe ON/OFF fluctuations treated by chronic daytime subcutaneous apomorphine infusion with supplemental oral levodopa were studied. On day 1, oral levodopa was withdrawn at 4:00 pm and on the following morning subcutaneous apomorphine infusion was continued at the same rate without levodopa therapy. While receiving apomorphine alone, seven of the eight patients turned ON, and their usual dyskinesias returned. The ON phase persisted for 60 to 100 minutes (mean, 185.7 minutes) but then, despite continued, constant-rate apomorphine infusion to stabilize plasma levels, switched to an OFF phase. The authors conclude that the clinical effect of apomorphine is sustained by levodopa long-duration response. This effect is probably the result of postsynaptic mechanisms. In patients with advanced Parkinson's disease, the long-duration response to levodopa is present although slightly diminished.

Apomorphine monotherapy in the treatment of refractory motor complications of Parkinson's disease: long-term follow-up study of 64 patients

Continuous subcutaneous infusion of apomorphine is now increasingly recognized as an effective treatment for refractory off periods and peak-dose dyskinesias in Parkinson's disease. We have reviewed our experience with apomorphine infusions, after a strategy decision in 1995 based on emerging preclinical data, to treat all patients with steady-state plasma levels of apomorphine throughout the waking day, minimizing additional pulsatile stimulation either by oral dopaminergic medication or bolus parenteral injections of apomorphine. Sixty-four patients have been treated with apomorphine pumps and 45 of these successfully converted to monotherapy, managing to discontinue all other forms of dopaminergic stimulation during the daytime treatment period with apomorphine. Patients were followed up for a mean of 33.8 months (range, 4-108 months) and clinical data analyzed retrospectively. The mean maintenance dose of apomorphine was 98 mg per 24 hours (monotherapy group: 103 mg/24 hours; polytherapy group: 93 mg/24 hours), which did not significantly increase at final follow-up. There was a mean maximum dyskinesia reduction of 64% (S.D. = 20) in the monotherapy group, compared to 30% (S.D. = 33) in those continuing on polytherapy (P < 0.001), despite a maintained increase in on time (monotherapy group: 55%, P < 0.005; polytherapy group: 50%, P = 0.05). Fifteen patients failed to successfully convert to monotherapy but benefited nonetheless, and only 3 failed apomorphine infusional therapy altogether. Reasons for failure were mixed, including difficulty with compliance and adverse effects such as daytime somnolence, skin complications, and painful dystonias. There was a significantly higher success rate in patients able to manage the treatment either independently or with the help of their caregiver. These results confirm that subcutaneous apomorphine monotherapy can reset peak-dose dyskinesia threshold in levodopa-treated patients and further reduce off-period disability after all available forms of oral medication, including long-acting dopamine agonists, have been tried.

Morphological and biochemical evidence that apomorphine rescues striatal dopamine terminals and prevents methamphetamine toxicity

Apomorphine, given by a single injection, repeated injections, or by continuous infusion, was tested for neuroprotective effects in mice administered methamphetamine or N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in order to induce striatal dopamine (DA) depletion. In the first part of the study, the DA agonist (R)-apomorphine was administered at various doses (1, 5, and 10 mg/kg), 15 min before methamphetamine (5 mg/kg x 3, 2 h apart). Mice were sacrificed 5 days later. In the second part, apomorphine was administered either continuously by subcutaneous minipump (cumulative daily dose of 0.5, 1, and 3.15 mg/kg), or as single, repeated daily injections (up to 5 mg/kg) starting 40 h after an acute administration of MPTP (30 mg/kg). Mice were sacrificed at different time intervals (up to 1 month) following MPTP injection. In all the animals, the integrity of striatal DA terminals was evaluated by measuring striatal DA levels and TH immunohistochemistry. Apomorphine dose-dependently prevented methamphetamine toxicity. These effects were neither due to a decrease in the amount of striatal methamphetamine nor to the hypothermia, and they were not reversed by the DA antagonist haloperidol. Moreover, chronic, continuous (but not pulsatile) administration of apomorphine rescued damaged striatal dopaminergic terminals. These findings confirm a protective effect of apomorphine that also consists of a neurorescue of damaged striatal DA terminals. This suggests a new hypothesis about the long-term benefits observed during continuous apomorphine administration in Parkinson's disease patients.

Continuous subcutaneous infusion of apomorphine rescues nigro-striatal dopaminergic terminals following MPTP injection in mice

Apomorphine has been introduced in the treatment of late-stage Parkinson's Disease (PD). The disadvantage of a short half-life of apomorphine is now overcome by the use of a continuous subcutaneous (s.c.) self-delivering system. We examined whether continuous s.c. infusion of apomorphine rescues nigro-striatal dopaminergic neurons from toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice. Apomorphine was continuously infused in mice by means of a s.c. minipump that delivered the drug at a rate of 0.5 or 3.15 mg/kg/day. MPTP induced a >80% reduction in striatal dopamine (DA) after one day. DA levels were still substantially reduced one month following MPTP injection, in spite of a partial recovery. Similarly, striatal immunoreactivity for tyrosine hydroxylase and dopamine transporter was markedly reduced at this time interval. Continuous s.c. infusion of apomorphine starting 40 h following MPTP injection rescued striatal dopaminergic terminals, as assessed by measurements of DA and its metabolites, as well as TH and DAT immunostaining after one month. The neurorescuing effect was more remarkable at a delivery rate of 3.15 mg/kg/day of apomorphine. In contrast, no rescue was observed when apomorphine was administered as a single daily s.c. bolus of 1 or 5mg/kg starting 40 h following MPTP. We conclude that apomorphine is able to rescue nigro-striatal dopaminergic neurons when continuously delivered at doses that are comparable to those delivered by minipumps in PD patients. These results suggest that continuous s.c. infusion of apomorphine not only relieves the symptoms, but also reduce the ongoing degeneration of nigro-striatal dopaminergic neurons in PD patients.

Iron chelating, antioxidant and cytoprotective properties of dopamine receptor agonist; apomorphine

There have been many attempts to discover neuroprotective drugs for the treatment of Parkinson's disease (PD). Many of these compounds either do not cross the blood brain barrier or are not very effective in the 6-hydroxydopamine or MPTP (N-methyl-4-phenyl-1,2,3,6-terahydropyridine) models of PD. We have examined several compounds including dopamine receptor agonist bromocritine, lisuride, pergolide and R-apomorphine for their neuroprotective action against the above neurotoxins in PC12 and dopamine neuroblastoma cell lines in culture and in vivo. R-apomorphine exhibited relatively potent neuroprotective action in vitro, cell culture and in vivo as a radical scavenger and iron chelator, because of its catechol structure. The recent clinical trials with apomorphine, where parkinsonian subjects can be weaned off L-dopa would suggest that this drug either exerts a neuroprotective action or that continuous sustained stimulation of dopamine receptor may be responsible for its unusual pharmacological activity. Apomorphine has a far more broad neuroprotective activity in the various models as compared with 1-selegiline and may therefore be an ideal drug to study neuroprotection in parkinsonian subjects with the use of PET or SPECT.

The pharmacokinetic and clinical effects of tolcapone on a single dose of sublingual apomorphine in Parkinson's disease

Apomorphine (APO) is a potent dopamine agonist that is partially metabolized by catachol-O-methyl transferase (COMT). Tolcapone was the first COMT inhibitor available for use as adjunctive therapy to levodopa in Parkinson's disease (PD). In order to determine whether this compound might increase the serum area under the curve (AUC) of APO and whether this results in any clinical benefit, we administered 200mg doses of tolcapone to five fluctuating PD patients taking an investigational sublingual APO preparation. Serial tapping speed and gait speed were assessed at 15min intervals over four hours, in conjunction with APO serum levels, following a single dose of APO, both before and five days after starting tolcapone (600mg/day). Serum APO levels tended to be higher (12.6%), and clinical measures suggested improvement during the APO "on" period after the addition of tolcapone (22.5% improvement in gait speed, and 7.6% improvement in tapping speed), but neither reached statistical significance. Further trials, involving larger samples are needed to clearly establish the pharmacokinetic and clinical effect of tolcapone in PD patients taking APO.

Continuous dopamine-receptor stimulation in advanced Parkinson's disease

Intermittent or pulsatile dopamine-receptor stimulation is postulated to induce plastic changes in motor systems that are responsible for the development of the motor fluctuations and dyskinesia that complicate long-term L-dopa therapy of Parkinson's disease. As a corollary to this hypothesis, continuous dopamine-receptor stimulation can avoid or reverse these complications. Such continuous stimulation is unlikely to mimic completely the normal function of the dopaminergic system, but should avoid the supra-physiological swings in extracellular dopamine that accompany intermittent L-dopa dosing. The concern is that this continuous stimulation might induce tolerance rather than sensitization to some effects of L-dopa. Open clinical trials support the value of continuous dopaminergic stimulation in Parkinson's disease with established motor complications, but rigorous studies, although experimentally difficult, are needed.

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.

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.

The pivotal role of iron in NF-kappa B activation and nigrostriatal dopaminergic neurodegeneration. Prospects for neuroprotection in Parkinson's disease with iron chelators

R-Apomorphine (APO) the catechol-derived dopamine D1-D2 receptor agonist has been shown to be highly potent iron chelator and radical scavenger and inhibitor of membrane lipid peroxidation in vitro, in vivo and in cell culture employing PC12 cells. Its potency has been compared to the prototype iron chelator desferrioxamine (desferal), dopamine, nifedipine and dopamine D2 receptor agonists, bromocriptine, lisuride, pergolide and pramipexole. APO also inhibits brain and mitochondrial protein oxidation. In vivo APO protects against MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)- induced striatal dopaminergic neurodegeneration in C57 black mice with as low as 5 mg/kg. APO is a reversible competitive inhibitor of monoamine oxidase (MAO) A and B with IC50 values of 93 and 214 uM, respectively. The iron chelating and radical scavenging actions of desferal and APO explains their ability to inhibit iron and 6-hydroxydopamine (6-OHDA)-induced neurodegeneration and activation of redox-sensitive transcription factor NF-kappa B and the subsequent transactivation of promoters of genes involved in inflammatory cytokines. Iron is thought to play a pivotal role in neurodegeneration, and APO may be an ideal drug to investigate neuroprotection in Parkinson's disease where iron and oxidative stress have been implicated in the pathogenesis of nigrostriatal dopamine neuron degeneration.

A novel sublingual apomorphine treatment for patients with fluctuating Parkinson's disease

We tested a novel preparation of a sublingual apomorphine hydrochloride tablet (APO) in 10 patients with advanced Parkinson's disease complicated by motor fluctuations. After a dose titration, patients took either 40 mg APO three times per day alternating with levodopa doses (eight patients) or six doses of 20 mg APO taken concurrently with levodopa doses (two patients) for 3 months. Assessments included timed tapping and ambulation tests, Unified Parkinson's Disease Rating Scale (UPDRS), and patient diaries. Tapping speed while taking only APO (12 hours after stopping levodopa) was faster than while taking only levodopa (p <0.05). The daily levodopa dose decreased by 32.1% (p <0.01), yet the total "on" time increased from 73.5% +/- 10.2% to 81.5% +/- 7.5% of the day (p <0.01) after starting APO. "On" UPDRS part II scores (p <0.05) and "on" UPDRS part III (motor examination) scores (p <0.05) also improved. Adverse events such as nausea, orthostatic hypotension, and disagreeable taste did not limit the dose of APO in any case. The short-term benefit and tolerability demonstrated in this study warrant further study of this new APO preparation.

Apomorphine protects against MPTP-induced neurotoxicity in mice

R-apomorphine is a potent radical scavenger and iron chelator. The neuroprotective property of R-apomorphine, a dopamine D1-D2 receptor agonist, has been studied in the MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) model of Parkinson's disease. Pretreatment with 5-10 mg/kg R-apomorphine administered subcutaneously in C57BL mice protects against MPTP (24 mg/kg administered intraperitoneally) induced loss of nigrostriatal dopamine neurons as indicated by striatal dopamine content, tyrosine hydroxylase content, and tyrosine hydroxylase activity. In vitro, R-apomorphine inhibited mice striatal MAO-A and MAO-B activities with IC50 values of 93 microM and 241 microM. It is suggested that the neuroprotective effect of R-apomorphine against MPTP neurotoxicity derives from its radical scavenging and MAO inhibitory actions and not from its agonistic activity because the mechanism of MPTP dopaminergic neurotoxicity involves the generation of oxygen radical species-induced oxidative stress.

Free radical scavengers: chemical concepts and clinical relevance

Free radicals are involved in the pathology of many CNS disorders, like Parkinson's disease, Alzheimer's disease, or stroke. This discovery lead to the development of many radical scavengers for the clinical treatment of neurodegenerative diseases. In this review, the different chemical concepts for free radical scavenging will be discussed: nitrons, thiols, iron chelators, phenols, and catechols. Especially catechols, like the naturally occurring flavonols, the synthetic drug nitecapone, or the endogenous catacholamines and their metabolites, are of great interest, as they combine iron chelating with radical scavenging activity. We present data on the radical scvenging activity of dopamine and apomorphine, which prevent lipid peroxidation in rat brain mitochondria and protect PC12 cells against H2O2-toxicity.

Potent neuroprotective and antioxidant activity of apomorphine in MPTP and 6-hydroxydopamine induced neurotoxicity

Apomorphine is a potent radical scavenger and iron chelator. In vitro apomorphine acts as a potent iron chelator and radical scavenger with IC50 of 0.3 microM for iron (2.5 microM) induced lipid peroxidation in rat brain mitochondrial preparation, and it inhibits mice striatal MAO-A and MAO-B activities with IC50 values of 93 microM and 241 microM. Apomorphine (1-10 microM) protects rat pheochromocytoma (PC12) cells from 6-hydroxydopamine (150 microM) and H2O2 (0.6 mM) induced cytotoxicity and cell death. The neuroprotective property of (R)-apomorphine, a dopamine D1-D2 receptor agonist, has been studied in the MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) model of Parkinson's disease. (R)-apomorphine (5-10 mg/kg, s.c.) pretreatment in C57BL mice, protects against MPTP (24 mg/kg, i.p.) induced loss of nigro-striatal dopamine neurons, as indicated by striatal dopamine content, tyrosine hydroxylase content and tyrosine hydroxylase activity. It is suggested that the neuroprotective effect of (R)-apomorphine against MPTP neurotoxicity derives from its radical scavenging and MAO inhibitory actions and not from its agonistic activity, since the mechanism of MPTP dopaminergic neurotoxicity involves the generation of oxygen radical species induced-oxidative stress.

A randomized, double-blind study of a skin patch of a dopaminergic agonist, piribedil, in Parkinson's disease

This randomized, double-blind trial was designed to evaluate the efficacy of a transdermal system of piribedil on the motor symptoms of Parkinson's disease during 3 weeks of treatment administered to three different groups: placebo, one piribedil patch (1 PP), and two (2 PP) piribedil patches. Twenty-seven patients with idiopathic Parkinson's disease, treated with L-dopa but not sufficiently controlled, were included in this trial. The test treatment did not demonstrate any clinical efficacy on either the main end point (Unified Parkinson's Disease Rating Scale motor score) or the secondary end points (rigidity, bradykinesia, postural, and resting tremor scores). The main adverse events were nausea (11%), vomiting (7.4%), and malaise (7.4%) mainly observed in the placebo group (four of seven patients). The local acceptability of the transdermal system was good. Plasma piribedil concentrations at the end of treatment were 6.74+/-1.10 and 9.31+/-3.33 ng/mL in the 1 PP and 2 PP groups, respectively. These plasma levels could account for the lack of clinical efficacy, because a previous pharmacokinetics-PD study conducted in parkinsonian patients and treated with the intravenous route demonstrated that the critical limits of activity on tremor were between 10 and 30 ng/mL.

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.

Subcutaneous apomorphine in late stage Parkinson's disease: a long term follow up

OBJECTIVES

Despite the recent introduction of new peroral drugs as well as neurosurgical methods for Parkinson's disease, treatment of late stage parkinsonian patients remains difficult and many patients become severely handicapped because of fluctuations in their motor status. Injections and infusions of apomorphine has been suggested as an alternative in the treatment of these patients, but the number of studies describing the effects of such a treatment over longer time periods is still limited. The objective was to investigate the therapeutic response and range of side effects during long term treatment with apomorphine in advanced Parkinson's disease.

METHODS

Forty nine patients (30 men, 19 women; age range 42-80 years) with Parkinson's disease were treated for 3 to 66 months with intermittent subcutaneous injections or continuous infusions of apomorphine.

RESULTS

Most of the patients experienced a long term symptomatic improvement. The time spent in "off" was significantly reduced from 50 to 29.5% with injections and from 50 to 25% with infusions of apomorphine. The quality of the remaining "off" periods was improved with infusion treatment, but was relatively unaffected by apomorphine injections. The overall frequency and intensity of dyskinesias did not change. The therapeutic effects of apomorphine were stable over time. The most common side effect was local inflammation at the subcutaneous infusion site, whereas the most severe were psychiatric side effects occurring in 44% of the infusion and 12% of the injection treated patients.

CONCLUSION

Subcutaneous apomorphine is a highly effective treatment which can substantially improve the symptomatology in patients with advanced stage Parkinson's disease over a prolonged period of time.

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.

Costs of drug treatment in Parkinson's disease

Parkinson's disease (PD) has a major socioeconomic impact on society. The chronic, progressive course of the disease, which often leads to severe disability, results in high expenses for the medical resources used for treatment, care, and rehabilitation of patients as well as reduced or lost productivity as a result of illness or premature death. In Great Britain, it has been estimated that the National Health Service spends up to 383 million pound sterling (1992) annually for the care of PD. This emphasizes the importance of assessing the costs related to this disease. A detailed knowledge of the cost allocation would provide a solid basis on which health care priorities can be rationally set. Next to hospitalization, drug treatment accounts for the highest expense for direct medical costs of PD. Therefore, this analysis focuses on the costs of drug treatment for PD. The cost analysis was based on a retrospective study of 409 patients with PD who were seen over a 1-year period in our movement disorders clinic. The cost of therapy varied considerably depending on the severity of the condition (assessed in the "off" phase), the incidence of motor fluctuations, and the type of PD. In the early stage of the disease (Hoehn and Yahr stage I [HY I]), mean daily costs for therapy were DM (German marks) 6.60, which increased in later stages of the disease (HY V) to DM 22.00. If rare cases requiring continuous subcutaneous apomorphine infusion were included, mean daily costs of patients in HY V rose to DM 32.50 (the mean daily costs of subcutaneous apomorphine-treated patients in HY V: DM 74.30). Patients with motor fluctuations accounted for higher costs (DM 16.50) compared with those without motor fluctuations (DM 7.80). With respect to the three subtypes of PD, the mean daily expenditure was DM 7.00 for the tremor-dominant type, DM 12.40 for the akinetic-rigid type, and DM 10.80 for the mixed type. In the group of 409 PD patients included in this analysis, the average daily expenditure for drug treatment totaled DM 10.70 per patient (including patients on subcutaneous apomorphine).

Increased cortical inhibition induced by apomorphine in patients with Parkinson's disease

The electromyographic silent period following the motor potential evoked by cortical magnetic stimulation is decreased in parkinsonian patients. In this study we investigated whether the decrease in the silent period is connected only with parkinsonian symptoms. We evaluated the effect of apomorphine (a potent and rapid dopamine-agonist) on the changes in the peripheral and central silent period in 29 patients with Parkinson's disease and in two patients affected by multisystem atrophy (MSA). Apomorphine injection was found to induce a significant improvement in the central silent period in parkinsonian patients but not in the MSA patients, suggesting a relation between the clinical parkinsonian symptoms (akinesia and rigidity) and the silent period duration. The central silent period changes after apomorphine injection could be used as an adjunctive, safe and effective diagnostic tool to assess dopamine responsiveness of parkinsonian syndromes.

Assay of R-apomorphine, S-apomorphine, apocodeine, isoapocodeine and their glucuronide and sulfate conjugates in plasma and urine of patients with Parkinson's disease

Analytical methods are described for the selective, rapid and sensitive determination of R- and S-apomorphine, apocodeine and isoapocodeine and the glucuronic acid and sulfate conjugates in plasma and urine. The methods involve liquid-liquid extraction followed by high-performance liquid chromatography with electrochemical detection. The glucuronide and sulfate conjugates are determined after enzymatic hydrolysis. For the assay of R- and S-apomorphine a 10 microm Chiralcel OD-R column is used and the voltage of the detector is set at 0.7 V. The mobile phase is a mixture of aqueous phase (pH 4.0)-acetonitrile (65:35, v/v). At a flow-rate of 0.9 ml min(-1) the total run time is ca. 15 min. The detection limits are 0.3 and 0.6 ng ml(-1) for R- and S- apomorphine, respectively (signal-to-noise ratio 3). The intra- and inter-assay variations are <5% in the concentration range of 2.5-25 ng ml(-1) for plasma samples, and <4% in the concentration range of 40-400 ng ml(-1) for urine samples. For the assay of apomorphine, apocodeine and isoapocodeine, a 5 microm C18 column was used and the voltage of the detector set at 0.825 V. Ion-pairing chromatography was used. The mobile phase is a mixture of aqueous phase (pH 3.0)-acetonitrile (75:25, v/v). At a flow-rate of 0.8 ml min(-1) the total run time is ca. 14 min. The detection limits of this assay are 1.0 ng ml(-1) for apomorphine and 2.5 ng ml(-1) for both apocodeine and isoapocodeine (signal-to-noise ratio 3). The inter-assay variations are 5% in the concentration range of 5-40 ng ml(-1) for plasma samples and 7% in the concentration range of 50-500 ng ml(-1) for urine samples. The glucuronic acid and sulfate conjugates of the various compounds are hydrolysed by incubation of the samples with beta-glucuronidase and sulfatase type H-1, respectively. Hydrolysis was complete after 5 h of incubation. No measurable degradation of apomorphine, apocodeine and isoapocodeine occurred during the incubation. A pharmacokinetic study of apomorphine, following the intravenous infusion of 30 microg kg(-1) for 15 min in a patient with Parkinson's disease, demonstrates the utility of the methods: both the pharmacokinetic parameters of the parent drug and the appearance of apomorphine plus metabolites in urine could be determined.