Apomorphine in idiopathic restless legs syndrome: an exploratory study

'Dopamine agonist Phobia' in Parkinson's disease: when does it matter? Implications for non-motor symptoms and personalized medicine

INTRODUCTION

Dopamine agonists have been widely used to treat patients with Parkinson's disease, but concerns related to their well-known side effects might prevent their use even when indicated. In this review, the authors describe for the first time the concept of 'Dopamine Agonist Phobia', a pharmacophobia that the authors believe might affect clinicians, and they provide evidence of the benefits of dopamine agonists, focusing on non-motor symptoms.

AREAS COVERED

The authors performed an extensive literature research, including studies exploring the use of dopamine agonists for the treatment of non-motor symptoms. The authors indicate the highest level of evidence in each section.

EXPERT OPINION

'Dopamine Agonist Phobia' may preclude valid therapeutic options in selected cases, specifically for the treatment of non-motor symptoms. Thus, the authors propose a personalized approach in Parkinson's disease treatment, and encourage a thoughtful use of dopamine agonists, rather than an overall nihilism.

New tricks for an old dog: A repurposing approach of apomorphine

Apomorphine is a 150-year old nonspecific dopaminergic agonist, currently indicated for treating motor fluctuations in Parkinson's disease. At the era of drug repurposing, its pleiotropic biological functions suggest other possible uses. To further explore new therapeutic and diagnostic applications, the available literature up to July 2018 was reviewed using the PubMed and Google Scholar databases. As many of the retrieved articles consisted of case reports and preclinical studies, we adopted a descriptive approach, tackling each area of research in turn, to give a broad overview of the potential of apomorphine. Apomorphine may play a role in neurological diseases like restless legs syndrome, Huntington's chorea, amyotrophic lateral sclerosis, Alzheimer's disease and disorders of consciousness, but also in sexual disorders, neuroleptic malignant(-like) syndrome and cancer. Further work is needed in both basic and clinical research; current developments in novel delivery strategies and apomorphine derivatives are expected to open the way.

The Many Faces of Apomorphine: Lessons from the Past and Challenges for the Future

Apomorphine is now recognized as the oldest antiparkinsonian drug on the market. Though still underused, it is increasingly prescribed in Europe for patients with advanced Parkinson's disease (PD) with motor fluctuations. However, its history is far from being limited to movement disorders. This paper traces the history of apomorphine, from its earliest empirical use, to its synthesis, pharmacological development, and numerous indications in human and veterinary medicine, in light of its most recent uses and newest challenges. From shamanic rituals in ancient Egypt and Mesoamerica, to the treatment of erectile dysfunction, from being discarded as a pharmacological tool to becoming an essential antiparkinsonian drug, the path of apomorphine in the therapeutic armamentarium has been tortuous and punctuated by setbacks and groundbreaking discoveries. Throughout history, three main clinical indications stood out: emetic (gastric emptying, respiratory disorders, aversive conditioning), sedative (mental disorders, clinical anesthesia, alcoholism), and antiparkinsonian (fluctuations). New indications may arise in the future, both in PD (palliative care, nonmotor symptoms, withdrawal of oral dopaminergic medication), and outside PD, with promising work in neuroprotection or addiction.

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.

The relevance of dopaminergic level in nocturnal disability in Parkinson's disease: implications of continuous dopaminergic stimulation at night to treat the symptoms

Sleep problems are an under-emphasized cause of disability in Parkinson's disease (PD). Difficult sleep maintenance (light and fragmented sleep) and difficulties in initiating sleep are often the earliest and the most frequent symptoms observed in PD patients. In fluctuating patients, nocturnal akinesia, dystonia, painful cramps, and parasomnias may aggravate nocturnal problems. Treatment of sleep problems can be complex and challenging for the physicians. Dopaminergic treatment may improve some of the nocturnal symptoms in PD. In this paper, the effect of drugs and technique that ensure a more continuous delivery of dopaminergic drugs on sleep problems in PD is reviewed.

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.

Subcutaneous apomorphine and non-motor symptoms in Parkinson's disease

Non-motor symptoms (NMS) are now recognized to occur across all stages of Parkinson's disease (PD) and as a result there has been an increasing focus on their diagnosis, quantification and effective management. While in some subjects, NMS may be present before diagnosis, in advanced PD, NMS can contribute to hospitalization, severe disability and a shortened life expectancy. Strategies for continuous drug delivery have been reported to have a beneficial effect on NMS in PD and while the efficacy of apomorphine on motor function in PD has been confirmed in a number of studies, in addition to its possible anti-dyskinetic effect, a number of reports have also outlined the possible beneficial effect of apomorphine on NMS. This review sets out to examine the efficacy of apomorphine in non-motor aspects of PD, including its effect on neuropsychiatric and gastrointestinal symptoms, sleep (including restless legs syndrome), urinary dysfunction, pain and impulse control disorders. The analysis takes into consideration case reports, and open-label and comparative case-control studies published to date. Results of this review suggest that although data on the effect of apomorphine on NMS in PD patients are limited there is a strong suggestion of a beneficial effect that warrants further investigation in double-blind studies.

Neurons of the dopaminergic/calcitonin gene-related peptide A11 cell group modulate neuronal firing in the trigeminocervical complex: an electrophysiological and immunohistochemical study

Activation of spinal trigeminal afferents innervating the cranial vasculature is likely to play a role in migraine, although some parts of the clinical presentation may have a dopaminergic basis. The A11 nucleus, located in the posterior hypothalamus, provides the only known source of descending dopaminergic innervation for the spinal gray matter. Extracellular recordings were made in the trigeminocervical complex (TCC) in response to electrical stimulation of the dura mater. Receptive fields were characterized by mechanical noxious and innocuous stimulation of the ipsilateral ophthalmic dermatome. Stimulation of the A11 significantly inhibited peri-middle meningeal artery dural and noxious pinch evoked firing of neurons in the TCC. This inhibition was reversed by the D(2) receptor antagonist eticlopride. Lesioning of the A11 significantly facilitated dural and noxious pinch and innocuous brush evoked firing from the TCC. In previous work using immunohistofluorescence, it was shown that D(1) and D(2) receptors were found in the rat TCC, and here we report, in addition, that D(4) and D(5) dopamine receptors are also present, whereas D(3) receptors are not. No dopamine receptors were present in the A11 nucleus itself. However, the A11 does contain dopamine and calcitonin gene-related peptide (CGRP) and, by this combination, is distinct from the neighboring CGRPergic subparafascicular nucleus. Exploration of dopaminergic influences and mechanisms in migraine may open up an almost untapped opportunity to pursue potential new therapeutic options for the disorder.

Restless legs syndrome: a common disorder in patients with rheumatologic conditions

OBJECTIVES

To review the symptoms, differential diagnosis, and treatment of the restless legs syndrome (RLS), and its relevance within rheumatologic practice.

METHODS

Review of the scientific literature on RLS to summarize symptom presentation, burden, diagnosis, treatment, and association with rheumatologic conditions.

RESULTS

RLS is a sensorimotor neurological disorder characterized by an irresistible urge to move the legs, usually accompanied or caused by unpleasant sensations within the legs. These sensations are sometimes described as achy or painful. They may cause sleep disruption and impair quality of life. RLS may be primary, of unknown etiology, with a likely genetic basis, or secondary, provoked by other conditions. Secondary RLS often improves when the underlying condition is treated or resolves. Since RLS is common in rheumatologic disorders such as rheumatoid arthritis or Sjögren's syndrome, rheumatologists need to be familiar with the condition. Primary care physicians may misattribute RLS symptoms to other conditions and refer patients to specialists for treatment. Since RLS symptoms can be similar to, and mistaken for, symptoms in rheumatologic diseases, patients may be referred to rheumatologists. Therefore, it is important that rheumatologists be able to recognize, differentiate, diagnose, and treat RLS.

CONCLUSIONS

The clinical diagnosis of RLS is based on 4 essential diagnostic criteria related to the urge to move that characterizes this disorder. Beyond good sleep hygiene and behavioral measures, dopaminergic agents are first-line treatments for primary RLS. Anticonvulsants, opioids, and sedative/hypnotics may also have a role in management.

First night efficacy of pramipexole in restless legs syndrome and periodic leg movements

OBJECTIVE

Restless legs syndrome (RLS) seems to improve immediately after a single dose of dopamine-agonists (DA). The aim of the present study was to investigate the acute effects of a low standard dose of pramipexole in RLS drug-naïve patients.

METHODS

A single-blind placebo-controlled study in 32 consecutive idiopathic RLS de-novo patients was carried out. Patients who met the standard criteria for RLS, with a PLMS index greater than 10 as well as an RLS rating scale score greater than 20 underwent clinical and neurophysiological evaluation, hematological screening and two consecutive full-night polysomnographies. On the second night, all patients received 0.25mg of pramipexole or placebo at 9:00 p.m. Acute symptom response was assessed by a visual analogical scale (VAS).

RESULTS

Eighteen patients received pramipexole and 14 patients received placebo. Compared to placebo, the single low dose (0.25mg) of pramipexole significantly improved RLS symptoms (VAS: from 7.4+/-1.68 to 1.3+/-1.62, p<0.00001) and strongly reduced PLMS index (from 45.8+/-33.56 to 9.4+/-11.40, p<0.0002). A significant increase in the percentage of stage 2 non-rapid eye movement (NREM) sleep was also observed in the pramipexole group (from 38.7+/-10.50 to 50.6+/-12.13, p<0.02).

CONCLUSIONS

A low dose of pramipexole was effective in treatment-naïve patients with RLS from the first night of administration. These results support a direct involvement of the dopaminergic system in RLS pathogenesis and might have important implications for a possible future pramipexole administration on-demand, as well as for a pharmacological test to confirm diagnosis in clinically complex cases.

Current guidelines and standards of practice for restless legs syndrome

Algorithms for treatment of restless legs syndrome (RLS) include both nonpharmacologic and pharmacologic therapy. Patients with RLS are divided into 3 groups: (1) those with intermittent RLS symptoms; (2) those with daily RLS symptoms; and (3) those whose symptoms are refractory to standard treatments. Many patients do not require medication, and symptoms often can be relieved with good sleep hygiene and avoidance of medications and factors that provoke symptoms. Recent large-scale clinical trials have proved the efficacy of therapy for RLS when it is required. Several classes of medications are helpful, but dopaminergic therapy appears to be most effective and relieves symptoms rapidly. The first step in managing RLS is to ensure that there is an adequate diagnosis; this involves discriminating RLS from other conditions that may share a number of features. Finally, it is important to tailor treatment to the needs of each individual patient.

Is daytime sleepiness a neglected problem in patients with restless legs syndrome?

The restless legs syndrome (RLS) is a common neurological disorder of sleep/wake motor regulation that is associated with sleep disturbances. Here, we review the evidence that RLS is also associated with increased daytime sleepiness. Summarizing 26 studies that assessed sleepiness by means of the Epworth Sleepiness Scale (ESS) in untreated subjects with idiopathic RLS, we found that 20 to 25% of subjects are at an increased risk for daytime sleepiness.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).

Test-to-test variability in motor activity during the suggested immobilization test in restless legs patients

BACKGROUND AND PURPOSE

To evaluate the test-to-test variability of the suggested immobilization test (SIT) in patients with restless legs syndrome (RLS).

PATIENTS AND METHODS

Twenty patients with primary RLS (12 men and eight women; age: 53.3+/-11.3 years) were selected for the study. We compared the results of two SITs performed on two consecutive evenings prior to polysomnographic recordings.

RESULTS

Overall, the periodic leg movement index during the SIT (SIT PLM) and the SIT PLM index associated with sensory manifestations (SIT PLM+) were not significantly different between tests. The number of PLM sequences per SIT, the mean PLM duration and the PLM interval did not significantly change between the two consecutive tests. The pattern of temporal evolution of motor activity across the SIT was very reproducible, SIT PLM showing a clear tendency to a progressive increase across the test, with the SIT PLM+ index decreasing in the second half of the test. Despite good reproducibility, there were marked intra-individual differences. Considering the proposed cut-off value of 12 for the SIT PLM index to confirm RLS, 11 patients were positive at the first test and four additional patients became positive at the second test. SIT PLM index changes did not correlate with age, severity of disease and polysomnographic measures.

CONCLUSIONS

Quantitative analysis of motor activity during two consecutive SITs in RLS patients showed a significant inter-test intra-individual variability unrelated to demographic, clinical or polysomnographic parameters. SIT PLM index variability suggests that a single test would not be sensitive enough for diagnostic purposes in unclear cases and that new criteria need to be applied to increase its specificity and sensitivity.

Emerging drugs for restless legs syndrome

Restless legs syndrome (RLS) is a common, but often underdiagnosed, neurological disorder, which is characterised by an imperative urge to move the extremities associated with paraesthesias, worsening of symptoms at rest and in the evening or at night, and, as a consequence, sleep disturbances. RLS affects 1-10% of the population. The aetiology of RLS is unknown, but besides genetic factors the dopaminergic and opioidergic system may play a crucial role and new developments also point to an exciting iron-dopamine connection in the pathophysiology of this burdening disorder. Due to the limited disease-specific knowledge, current treatment strategies are not curative, but nevertheless may produce an effective and lasting relief of symptoms. Although clinically based treatment has focused on levodopa, opioids and benzodiazepines for a long time, evidence-based and clinical guidelines identify dopamine agonists as a first-line treatment for daily restless legs symptoms. These substances are now in the process of registration for this indication. Ropinirole is the first dopamine agonist that has been approved by the FDA in May 2005. In addition, several promising new therapies with nondopamine profiles are under development for RLS.

Dopamine agonists for the treatment of restless legs syndrome

The restless legs syndrome is a neurological disorder characterised by the urge to move the extremities associated with paraesthesias, which are partially or totally relieved by movement, a worsening of symptoms at rest and in the evening or at night and, as a consequence, sleep disturbances. Restless legs syndrome is common and affects 1-10% of the population. The aetiology of restless legs syndrome is unknown, but, beside genetic factors, the dopaminergic system may play a crucial role. Current treatment strategies are not curative, but may nevertheless produce an effective and lasting relief of symptoms. Evidence-based and clinical guidelines identify dopamine agonists as a first-line treatment for daily restless legs symptoms, and such substances are in the process of registration for this indication. In May 2005, the first dopamine agonist, ropinirole, was approved by the FDA. This review discusses treatment studies of dopamine agonists in patients with restless legs syndrome and focuses on long-term treatment with dopamine agonists.

Treatment of sleep disorders in elderly patients

Sleep disorders are common among the elderly and are associated with diminished quality of life, increased risk for development of psychiatric disorders, inappropriate use of sleep aids, and decreased daytime functioning. The most common and important sleep disorders in the elderly include insomnia, obstructive sleep apnea syndrome, restless legs syndrome, rapid eye movement sleep behavior disorder, and the advanced sleep phase syndrome. In this article, we summarize the current treatment strategies for each of these sleep-related disorders. Before contemplating specific treatments, the authors recommend that more conservative and nonpharmacologic therapies be attempted first because the elderly are more likely to have medication side effects or complications related to surgery. Many sleep problems can be treated by simple sleep hygiene modifications that can be implemented and adopted easily. For others, therapies that specifically consider older adults may be required. For each of the sleep disorders we provide an updated discussion of therapies beginning with diet and lifestyle, pharmacologic treatment, interventional procedures, surgery, assistive devices, physical and speech therapy, exercise, and emerging therapies with specific considerations for older adults.