Suppression of dyskinesias in advanced Parkinson's disease: moderate daily clozapine doses provide long-term dyskinesia reduction

Clozapine Use in a Movement Disorder Clinic

BACKGROUND

Clozapine is an effective antipsychotic for Parkinson's disease (PD) that does not worsen motor function and can improve tremor. It is approved for PD psychosis in Europe and Australia.

OBJECTIVE

The aim of this study was to report on the use of clozapine in a movement disorder clinic.

METHODS

We report on patients monitored during the COVID-19 pandemic in clinic over a 7-month period.

RESULTS

Sixty-five patients were seen, of whom 50 had PD. Thirty-one were treated for psychosis, 18 for refractory tremor and 1 for levodopa dyskinesias. The remainder had psychotic symptoms with dementia with Lewy bodies (n = 2) or other movement disorders. Four had clozapine discontinued because of sedation and 1 for agranulocytosis. Three had clozapine temporarily halted because of granulocytopenia but were rechallenged successfully.

CONCLUSIONS

When comparing clozapine use in this clinic as compared with others, we deduce that clozapine is likely significantly underutilized in the United States.

D1/D5 Inverse Agonists Restore Striatal Cholinergic Interneuron Physiology in Dyskinetic Mice

BACKGROUND

In advanced stages of Parkinson's disease (PD), dyskinesia and motor fluctuations become seriously debilitating and therapeutic options become scarce. Aberrant activity of striatal cholinergic interneurons (SCIN) has been shown to be critical to PD and dyskinesia, but the systemic administration of cholinergic medications can exacerbate extrastriatal-related symptoms. Thus, targeting the mechanisms causing pathological SCIN activity in severe PD with motor fluctuations and dyskinesia is a promising therapeutic alternative.

METHODS

We used ex vivo electrophysiological recordings combined with pharmacology to study the alterations in intracellular signaling that contribute to the altered SCIN physiology observed in the 6-hydroxydopamine mouse model of PD treated with levodopa.

RESULTS

The altered phenotypes of SCIN of parkinsonian mice during the "off levodopa" state resulting from aberrant Kir/leak and Kv1.3 currents can be rapidly reverted by acute inhibition of cAMP-ERK1/2 signaling. Inverse agonists that inhibit the ligand-independent activity of D5 receptors, like clozapine, restore Kv1.3 and Kir/leak currents and SCIN normal physiology in dyskinetic mice.

CONCLUSION

Our work unravels a signaling pathway involved in the dysregulation of membrane currents causing SCIN hyperexcitability and burst-pause activity in parkinsonian mice treated with levodopa (l-dopa). These changes persist during off-medication periods due to tonic mechanisms that can be acutely reversed by pharmacological interventions. Thus, targeting the D5-cAMP-ERK1/2 signaling pathway selectively in SCIN may have therapeutic effects in PD and dyskinesia by restoring the normal SCIN function. © 2022 International Parkinson and Movement Disorder Society.

Medical Management and Prevention of Motor Complications in Parkinson's Disease

Levodopa is the most effective medication for the treatment of the motor symptoms of Parkinson's disease. However, over time, the clinical response to levodopa becomes complicated by a reduction in the duration and reliability of motor improvement (motor fluctuations) and the emergence of involuntary movements (levodopa-induced dyskinesia). Strategies that have been attempted in an effort to delay the development of these motor complications include levodopa sparing and continuous dopaminergic therapy. Once motor complications occur, a wide array of medical treatments is available to maximize motor function through the day while limiting dyskinesia. Here, we review the clinical features, epidemiology, and risk factors for the development of motor complications, as well as strategies for their prevention and medical management.

Pathophysiology of L-dopa-induced motor and non-motor complications in Parkinson's disease

Involuntary movements, or dyskinesia, represent a debilitating complication of levodopa (L-dopa) therapy for Parkinson's disease (PD). L-dopa-induced dyskinesia (LID) are ultimately experienced by the vast majority of patients. In addition, psychiatric conditions often manifested as compulsive behaviours, are emerging as a serious problem in the management of L-dopa therapy. The present review attempts to provide an overview of our current understanding of dyskinesia and other L-dopa-induced dysfunctions, a field that dramatically evolved in the past twenty years. In view of the extensive literature on LID, there appeared a critical need to re-frame the concepts, to highlight the most suitable models, to review the central nervous system (CNS) circuitry that may be involved, and to propose a pathophysiological framework was timely and necessary. An updated review to clarify our understanding of LID and other L-dopa-related side effects was therefore timely and necessary. This review should help in the development of novel therapeutic strategies aimed at preventing the generation of dyskinetic symptoms.

Evidence-based advances in the treatment of motor features of Parkinson’s disease

SUMMARY Evidence-based medicine evaluates evidence and synthesizes information to succinct conclusions and recommendations. Despite this, there are gaps for clinicians as many clinically relevant questions have not been examined. Guidelines with clear criteria for evaluating evidence (from the American Academy of Neurology, NICE and the Movement Disorders Society) are contrasted and important clinical issues that are not currently addressed will be highlighted. Through weighing both motor benefit and complications of therapy, clinicians may use levodopa for patients with a low risk of dyskinesia, or a higher risk of confusion, delirium or impulse control disorders, or pre-existing daytime sleepiness. For patients with higher risk of dyskinesia and a low risk of confusion, delirium and impulse control disorders, and without pre-existing daytime sleepiness, dopamine agonists may be the dopaminergic drug of choice. Evidence for treating motor complications of illness does not provide hierarchical choice. Evidence for surgical treatments is limited by practical issues of blinding surgery. Longer term complications of surgery need to be balanced with potential benefits of surgical procedures.

Psychiatric care in Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is a degenerative and disabling disease in which medical providers focus mainly on ameliorating problems in day-to-day functioning. This review summarizes current knowledge about the efficacy and tolerability of psychopharmacological agents in the treatment of depression, anxiety, psychosis, and insomnia in patients with PD. Recommended or promising nonpharmacological interventions are also reviewed.

METHOD

Studies were identified using computerized searches, with further references obtained from the bibliographies of the reviewed articles.

RESULT

Findings in the research literature provide growing evidence concerning the antidepressant treatment of patients with PD. Psychoeducational interventions for managing depression and anxiety symptoms also appear promising. Music therapy has proven to be particularly effective for patients with PD. Psychosis is common in patients with PD. When psychosis is induced by antiparkinson drugs, a dose reduction can be considered, but it is seldom successful. Patients with PD do not generally tolerate conventional antipsychotic medications, justifying evaluation of newer atypical agents in this population. Cholinesterase inhibitors have also become increasingly important in the treatment of PD in recent years. Finally, insomnia is a very frequent complaint in patients with PD and may also contribute to the development of depression. Patients should be encouraged to improve sleep hygiene and use behavioral interventions. Definitive trials of treatments for sleep disorders in this population are also warranted.

CONCLUSION

Therapeutic approaches to the treatment of PD and its associated psychiatric symptoms must be individualized and may involve a combination of antiparkinson drugs, psychopharmacological treatment, and/or psychotherapeutic interventions.

Treatment of motor symptoms in advanced Parkinson's disease: a practical approach

Patients with advanced Parkinson's disease (PD) are known to develop motor complications after a few years of levodopa (L-dopa) therapy. Motor fluctuations develop with increasing severity of the disease, owing to loss of dopaminergic neurons and loss of the buffering capacity of the neurons to fluctuating dopamine levels. Dyskinesias develop as a result of pulsatile stimulation of the receptors and alterations in neuronal firing patterns. L-dopa remains the gold standard medication for the treatment of patients with advanced PD. However, once motor complications on L-dopa therapy emerge, clinicians may add on other classes of antiparkinsonian drugs such as dopamine agonists, catechol-O-methyl transferase inhibitors (COMTIs) or monoamine oxidase type B inhibitors (MAOBIs). The individualisation of the treatment seems to be the key for the best approach of advanced PD patients. The present review provides the most important current clinical data in the pharmacological treatment of motor symptoms in advanced PD and provides the clinician a simple algorithm in order to determine the best suitable treatment to advanced parkinsonian patients.

The serotonergic system in Parkinson's disease

Although the cardinal manifestations of Parkinson's disease (PD) are attributed to a decline in dopamine levels in the striatum, a breadth of non-motor features and treatment-related complications in which the serotonergic system plays a pivotal role are increasingly recognised. Serotonin (5-HT)-mediated neurotransmission is altered in PD and the roles of the different 5-HT receptor subtypes in disease manifestations have been investigated. The aims of this article are to summarise and discuss all published preclinical and clinical studies that have investigated the serotonergic system in PD and related animal models, in order to recapitulate the state of the current knowledge and to identify areas that need further research and understanding.

Mechanisms of action of antipsychotic drugs of different classes, refractoriness to therapeutic effects of classical neuroleptics, and individual variation in sensitivity to their actions: Part I

Many issues remain unresolved about antipsychotic drugs. Their therapeutic potency scales with affinity for dopamine D2 receptors, but there are indications that they act indirectly, with dopamine D1 receptors (and others) as possible ultimate targets. Classical neuroleptic drugs disinhibit striatal cholinergic interneurones and increase acetyl choline release. Their effects may then depend on stimulation of muscarinic receptors on principle striatal neurones (M4 receptors, with reduction of cAMP formation, for therapeutic effects; M1 receptors for motor side effects). Many psychotic patients do not benefit from neuroleptic drugs, or develop resistance to them during prolonged treatment, but respond well to clozapine. For patients who do respond, there is a wide (>ten-fold) range in optimal doses. Refractoriness or low sensitivity to antipsychotic effects (and other pathologies) could then arise from low density of cholinergic interneurones. Clozapine probably owes its special actions to direct stimulation of M4 receptors, a mechanism available when indirect action is lost.

l-Dopa-induced dyskinesia-clinical presentation, genetics, and treatment

Levodopa-induced dyskinesia (LID) has been recognized since the introduction of levodopa for the management of Parkinson's disease (PD) and continues to be one of the most clinically challenging factors in long-term management of patients with PD. Most patients develop LID within 10 years of PD onset and the cause has been attributed to various factors including disease demographics, pharmacological, and possibly genetic causes. The clinical pattern of LID varies and shows intra and inter-patient variability and has been classified based upon phenomenology and relation to timing of levodopa. The potential armamentarium to address and manage LID has significantly increased in the last decade. This chapter addresses the current understanding of various clinical aspects and available therapeutics for LID.

Parkinson's disease psychosis 2010: a review article

Psychotic symptoms are common in Parkinson's disease (PD), generally associated with the medications used to treat the motor symptoms. On rare occasion they occur in patients not taking medication for PD. Psychotic symptoms are usually hallucinations, typically visual, less commonly auditory, and rarely in other domains. Hallucinations are generally stereotyped and without emotional content. Initially patients usually have insight so that the hallucinations are benign in terms of their immediate impact but have poor prognostic implications, with increased risk of dementia, worsened psychotic symptoms and mortality. Delusions occur in about 5-10% of drug treated patients and are considerably more disruptive, being paranoid in nature, often of spousal infidelity or abandonment by family. Treatment of Parkinson's disease psychosis (PDP) focuses on reducing the psychiatric symptom load while balancing the competing problem of mobility. Contributors to the psychotic symptoms should be searched for, such as systemic illness and other psycho-active medications. If none are identified or can be eliminated then the PD medications should be reduced to the lowest levels that allow tolerable motor function. Once this level has been reached there are two schools of thought on treatment, using either acetylcholinesterase inhibitors or atypical anti-psychotics. Only clozapine has level I evidence to support its use. Quetiapine is the only other anti-psychotic free of motor side effects, but it has failed double blind placebo controlled trials to demonstrate efficacy.

Current use of clozapine in Parkinson disease and related disorders

OBJECTIVE

Clozapine has been shown to be effective in the treatment of Parkinson disease psychosis and tremor; however, use of clozapine has been limited because of potential adverse effects and stringent monitoring criteria.

METHODS

To evaluate safety and efficacy in a naturalistic setting, we conducted a retrospective chart review of all patients ever treated with clozapine at a movement disorders clinic in Rhode Island.

RESULTS

Clozapine was indicated for psychosis in 39 patients, for tremor in 19, and for both tremor and psychosis in an additional 6 patients. Fifty of 61 patients reported improvement in their symptoms. Clozapine use was interrupted in 26 patients, for various reasons including transition to hospice care (3), worsening of motor symptoms (4), agranulocytosis (1), intolerable adverse effects (9), symptom resolution (2), and other or unknown reasons (7).

CONCLUSIONS

Clozapine may be useful in the management of movement disorders and related symptoms so long as adequate supervision and monitoring can be provided.

How do you treat motor complications in Parkinson's disease: Medicine, surgery, or both?

The motor complications associated with levodopa therapy, namely, fluctuations in motor response and dyskinesias, occur in the majority of Parkinson's disease patients. These complications can impair a patient's quality of life and even cause pronounced disability. "Off" states that result in freezing of gait and falling are disabling for many patients. Dyskinesias most commonly occur at peak dose and typically alternate with the wearing-off state. Once these problems appear, they usually persist, and the physician needs to make continual adjustments in medications to minimize these problems. Medical treatments should be attempted before treatments such as deep brain stimulation are considered because of the potential adverse effects that are associated with surgery. The timing of surgery, however, is also important because younger patients and less advanced patients tend to have a better outcome. There is thus a need for experienced and knowledgeable physicians and surgeons who are able to handle these motor complications. This review discusses available medications and surgical approaches, and their outcomes.

Enhancing aromatic L-amino acid decarboxylase activity: implications for L-DOPA treatment in Parkinson's disease

Aromatic L-amino acid decarboxylase (AAAD) is an essential enzyme for the formation of catecholamines, indolamines, and trace amines. Moreover, it is a required enzyme for converting L-DOPA to dopamine when treating patients with Parkinson's disease (PD). There is now substantial evidence that the activity of AAAD in striatum is regulated by activation and induction, and second messengers play a role. Enzyme activity can be modulated by drugs acting on a number of neurotransmitter receptors including dopamine (D1-4), glutamate (NMDA), serotonin (5-HT(1A), 5-HT(2A)) and nicotinic acetylcholine receptors. Generally, antagonists enhance AAAD activity; while, agonists may diminish it. Enhancement of AAAD activity is functional, as the formation of dopamine from exogenous L-DOPA mirrors activity. Following a lesion of nigrostriatal dopaminergic neurons, AAAD in striatum responds more robustly to pharmacological manipulations, and this is true for the decarboxylation of exogenous L-DOPA as well. We review the evidence for parallel modulation of AAAD activity and L-DOPA decarboxylation and propose that this knowledge can be exploited to optimize the formation of dopamine from exogenous L-DOPA. This information can be used as a blue print for the design of novel L-DOPA treatment adjuvants to benefit patients with PD.

Pharmacological treatment of Parkinson's disease: life beyond dopamine D2/D3 receptors?

Parkinson's disease (PD) is a multisystemic disorder in which several neurotransmitters other than dopamine are affected. Drugs acting on non-dopaminergic systems are envisaged as promising agents to treat PD and levodopa-induced dyskinesias (LID). However, compounds targeting glutamate, adenosine, noradrenaline, 5-hydroxytryptamine, cannabinoid, and opioid transmitter systems have been assessed in human studies showing negative, inconsistent or unsatisfactory results. Most of these drugs had been tested previously in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned monkeys, as well as in the classic 6-hydroxydopamine-lesioned rat model. These failures raise several questions and concerns about the true reliability of animal studies, the adequacy of the working hypotheses and design of clinical trials, the validity of tools in current use to evaluate a particular effect, and the selectivity of the drugs used. More importantly, observed discrepancies between the results in models and patients, could challenge the validity of current ideas about the pathophysiology of parkinsonism and LID.

Levodopa-induced Dyskinesia in Parkinson’s disease: Epidemiology, etiology, and treatment

Although levodopa is the gold standard for treating motor symptoms of Parkinson's disease (PD), long-term therapy leads to levodopa-induced dyskinesia (LID). Dyskinesia refers to involuntary movements other than tremor and most commonly consists of chorea that occurs when levodopa-derived dopamine is peaking in the brain ("peak-dose dyskinesia"). However, dyskinesia can also consist of dystonia or myoclonus and occur during other parts of the levodopa dosing cycle. New validated rating scales and home diaries can better help the health care provider assess the timing and severity of dyskinesia. The exact etiology of LID is unknown, but there is evidence that abnormal pulsatile stimulation of dopamine receptors may be contributory. Treatment of LID includes adjustment of PD medications to maximize "on" time without troublesome dyskinesia. Amantadine is the only medication available with demonstrated ability to reduce the expression of established LID without reducing antiparkinsonian benefit. Other medications that are currently being studied to treat established LID include antiepileptics and serotonergic medications. Deep brain stimulation of the subthalamic nucleus is now the most commonly used surgical procedure for PD patients, and it is very effective in treating LID.

Modulation of L-DOPA-induced abnormal involuntary movements by clinically tested compounds: further validation of the rat dyskinesia model

L-DOPA-induced dyskinesia (LID) is a major complication of the pharmacotherapy of Parkinson's Disease. A model of LID has recently been described in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions. In the present study, the model was used in order to compare the efficacies of some clinically available compounds that have shown antidyskinetic effects in nonhuman primate models of LID and/or in patients, namely, amantadine (20 and 40 mg/kg), buspirone (1, 2 and 4 mg/kg), clonidine (0.01, 0.1 and 1 mg/kg), clozapine (4 and 8 mg/kg), fluoxetine (2.5 and 5 mg/kg), propranolol (5, 10 and 20mg/kg), riluzole (2 and 4 mg/kg), and yohimbine (2 and 10 mg/kg). Rats were treated for 3 weeks with L-DOPA for an induction and monitoring of abnormal involuntary movements (AIMs) prior to the drug screening experiments. The antidyskinetic drugs or their vehicles were administered together with L-DOPA, and their effects were evaluated according to a randomized cross-over design both on the AIM rating scale and on the rotarod test. Most of the compounds under investigation attenuated the L-DOPA-induced axial, limb and orolingual AIM scores. However, the highest doses of many of these substances (but for amantadine and riluzole) had also detrimental motor effects, producing a reduction in rotarod performance and locomotor scores. Since the present results correspond well to existing clinical and experimental data, this study indicates that axial, limb and orolingual AIMs possess predictive validity for the preclinical screening of novel antidyskinetic treatments. Combining tests of general motor performance with AIMs ratings in the same experiment allows for selecting drugs that specifically reduce dyskinesia without diminishing the anti-akinetic effect of L-DOPA.

Medical management of advanced Parkinson's disease

The management of advancing Parkinson's disease (PD) is a daunting task, complicated by dynamic medication responses, side effects, and treatment-refractory symptoms in an aging patient population. The motor and nonmotor complications of advancing PD are reviewed, and practical treatment strategies are provided. Careful assessment in the context of the known natural history of advancing PD and rational treatment choices can create significant improvement in the lives of patients who have advancing PD.

Use of ziprasidone in parkinsonian patients with psychosis

Twelve patients with Parkinson disease and psychosis were included in an open-label 12-week trial of ziprasidone. Two patients withdrew from the treatment because of adverse effects. The remaining 10 patients reported a significant improvement in psychiatric symptoms. Altogether, there was no deterioration of motor symptoms (UPDRS III score: basal 40.4 +/- 11.1, first month 41.1 +/- 10.8; final visit, 37.7 +/- 13.3). Two patients (20%) suffered a slight deterioration in motor symptoms and another patient suffered deterioration of gait. No analytic alterations or serious adverse effects that could limit the use of ziprasidone were observed. Although controlled trials are needed, the findings suggest that ziprasidone may be effective in parkinsonian patients with psychosis.

Other pharmacological treatments for motor complications and dyskinesias

Controlling motor complications becomes increasingly difficult with disease progression. The "wearing-off" phenomenon is the most-common motor fluctuation. Wearing-off can be treated by dietary manipulation, shortening the dosing interval, substituting sustained-release levodopa, adding amantadine, or monoamine oxidase type B inhibitors, and other options, including catechol-O-methyltransferase inhibitors and the approved dopamine agonists addressed in another chapter. The rotigotine constant-delivery system is being developed to treat wearing-off symptoms. Istradefylline (KW-6002), an adenosine A(2A) receptor antagonist, has been studied for wearing-off and the results will be discussed. The on-off fluctuations can be treated with liquid levodopa and the rescue therapy of injectable apomorphine. Patients may also suffer from dyskinesias. Dyskinesias can be treated with small doses of liquefied levodopa-carbidopa, amantadine, and clozapine, an atypical neuroleptic.

Rationale for current therapies in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that affects an estimated 1 million people in the US and tens of millions worldwide. Medication therapy has made significant advances and improvements especially over the last 10 years. A number of new treatments and new strategies have emerged and the quality of life for the average sufferer has improved. This review will describe the rationale and strategies for current medical therapies in PD, with special emphasis on the use of antipsychotic agents. Levodopa remains the most efficacious medication for the management of PD. Long-term use of levodopa, however, is associated with the development of motor fluctuations including dyskinesia. Trials with dopamine agonists have demonstrated a delay in the onset of dyskinesia with the use of this therapy. There is also active, ongoing investigation to determine whether a neuroprotective effect may be present with agonist therapy. Anticholinergics have been successfully used to treat tremor as well as sialorrhoea and urinary urgency. Catechol-O-methyltransferase inhibitors increase 'on time', decrease 'off time,' and improve motor scores. Continuous stimulation of dopamine receptors may decrease the fluctations observed with pulsatile delivery of anti-Parkinsonian medications, but this will require more study. Monoamine oxidase-B inhibitors, specifically selegiline, may provide symptomatic improvement; the question as to whether a neuroprotective benefit is present remains unanswered. Amantadine has demonstrated both symptomatic benefit and dyskinesia benefit in some patients. Selective dopamine blockers such as clozaril and quetiapine, have been shown to be effective in the treatment of psychosis. This class of medications is particularly useful as an adjunctive to levodopa and dopamine agonists. Doses of dopaminergic drugs can be escalated to treat Parkinsonian symptoms, whereas selective dopamine blockers can be added to block psychosis. Old management strategies required a reduction in dopaminergic therapy and therefore worsened Parkinsonian symptoms. Even though there have been great advances in the medical options for symptomatic management of PD, there are still many unmet needs for this patient population.

Intrastriatal serotonin 5-HT2 receptors mediate dopamine D1-induced hyperlocomotion in 6-hydroxydopamine-lesioned rats

Striatal dopamine (DA) and serotonin (5-HT) functions are altered following DA denervation. Previous research indicates that intrastriatal coadministration of D1 and 5-HT2 receptor agonists synergistically increase locomotor behavior in DA-depleted rats. In the present study, we examined whether striatal 5-HT2 mechanisms also account for supersensitive D1-mediated locomotor behavior following DA denervation. Adult male Sprague-Dawley rats were subjected to bilateral striatal cannulation and then received either intracerebroventricular (i.c.v.) or intrastriatal 6-hydroxydopamine (6-OHDA; 200 microg or 20 microg/side, respectively). After at least 3 weeks, i.c.v.-lesioned rats received intrastriatal infusions of the 5-HT2 receptor antagonist ritanserin (2.0 microg/side) or its vehicle (DMSO) followed by systemic SKF 82958, a D1 agonist (1.0 mg/kg, i.p.) and locomotor activity was monitored. In another experiment, intrastriatal sham and 6-OHDA-lesioned rats received bilateral intrastriatal infusions of ritanserin (2.0 microg/side) or its vehicle (DMSO) followed by intrastriatal infusions of SKF 82958 (5.0 microg/side) or vehicle (0.9% saline). Rats with DA loss demonstrated supersensitive locomotor responses to both systemic and intrastriatal SKF 82958. Ritanserin pretreatment blunted systemic SKF 82958-induced hyperlocomotion and returned intrastriatal D1-mediated hyperactivity to sham lesion levels. The results of this study suggest that striatal 5-HT2 receptors contribute to D1-mediated hyperkinesias resulting from DA loss and suggest a pharmacological target for the alleviation of dyskinesia that can develop with continued DA replacement therapy.

The use of atypical antipsychotics in traumatic brain injury

The use of antipsychotic medication in treating individuals with traumatic brain injury (TBI) has been controversial. Much of the caution derives from animal studies (and limited human data) with regard to typical antipsychotics. Of note, however, is that similar assumptions have been made about the newer generation of atypical antipsychotics as well. Because these agents have different mechanisms of action as well as different neurotransmitter targets, this may very well be unwarranted. In this article, mechanisms of action of typical and atypical antipsychotics are discussed, with particular attention paid to their use in TBI. Indications and contraindications are presented, and recommendations are made for the responsible prescribing of antipsychotic medications after TBI.

Atypical antipsychotics in Parkinson-sensitive populations

Drug-induced iatrogenic hallucinations and psychosis occur in about 30% of Parkinson's disease (PD) patients and are the single most important precipitant for nursing home placement, which carries a grave prognosis. In addition, parkinsonism is a frequent accompaniment to the more common dementing syndromes, Alzheimer's disease (AD), vascular dementia, and dementia with Lewy bodies (DLB). The five most recent antipsychotic drugs approved by the Food and Drug Administration in the United States have been marketed as "atypical" antipsychotics (AA) due to their relative freedom from extrapyramidal symptoms when used in schizophrenia patients. The use of these newer antipsychotic drugs in PD and other parkinson-sensitive populations represents the most stringent test to their freedom from motor side effects. To date, clozapine, risperidone, olanzapine, and quetiapine have been studied in parkinson-vulnerable populations. This article reviews the data and highlights the differences that these four drugs have on motor function. It also emphasizes the challenges in evaluating the available data on the motor effects of AA, especially on the non-PD elderly and cognitively impaired population. Suggestions are made for future research to improve the interpretability of these studies.

Parkinson's disease: medical treatment of moderate to advanced disease

Parkinson's disease, a common neurodegenerative disorder, results in significant morbidity 10 to 15 years after disease onset and increased mortality. Levodopa is the mainstay of therapy and provides benefit for the duration of the illness. However, within 5 years, up to 50% of individuals develop fluctuations, including dyskinesias, wearing off, and "on/off" effects. Optimal management of Parkinson's disease patients requires careful titration of medications, with use of polypharmacy, including levodopa, dopamine agonists, catechol-O-methyltransferase inhibitors, amantadine, and anticholinergics in order to maintain good motor function and quality of life. With advancing disease, problems such as dysphagia, dysarthria, and gait and balance abnormalities occur, which are not responsive to dopaminergic medication. Due to extradopaminergic neuronal system degeneration, autonomic dysfunction can also be prominent. Recognition and management of these problems is helpful in improving quality of life in late-stage disease. In very late stages, dementia may complicate treatment, requiring discontinuation of combination therapy and use of low-dose levodopa with atypical neuroleptics.

Effects of newer antipsychotics on extrapyramidal function

Following acceptance of clozapine as a superior antipsychotic agent with low risk of adverse extrapyramidal syndromes (EPS), such as dystonia, parkinsonism, akathisia or tardive dyskinesia, several novel antipsychotic drugs have been developed with properties modelled on those of clozapine. Though generally considered 'atypical' in their relatively low risk of inducing EPS, these agents vary considerably in their pharmacology and impact on neurological functioning. Although few comparative data are available, the atypical antipsychotics can be tentatively ranked by EPS risk (excluding akathisia and neuroleptic malignant syndrome) in the following order: clozapine < quetiapine < olanzapine = ziprasidone. At higher doses, risperidone is ranked with a higher EPS risk than olanzapine and ziprasidone, but its risk of EPS is lower with lower doses. In general, this ranking is inversely related to antidopaminergic (D2 receptor) potency. The high antiserotonergic (5-HT2A receptor) potency of risperidone, clozapine, ziprasidone and olanzapine, but not quetiapine, as well as the antimuscarinic activity of olanzapine and clozapine may also limit EPS. For the treatment of psychotic reactions to dopamine agonist therapy in Parkinson's disease, clozapine is both effective and relatively well tolerated; quetiapine may be tolerated, olanzapine is not well tolerated, risperidone is poorly tolerated, and amisulpride and ziprasidone have not been well evaluated. Clozapine, perhaps because of its anticholinergic activity, can reduce parkinsonian tremor. It is useful for ongoing psychosis with tardive dyskinesia, especially for dystonic features. No atypical antipsychotic is clearly effective for motor abnormalities in Huntington's disease or Tourette's syndrome, and the effect of these drugs on other neurological disorders have been well evaluated in only small numbers of patients. In summary, with the exception of clozapine, and perhaps quetiapine, atypical antipsychotics have brought only relative avoidance of EPS, strongly encouraging continued searches for novel antipsychotic agents.

Parkinson's disease therapy: tailoring choices for early and late disease, young and old patients

Advances in the understanding of basal ganglia circuitry and its altered function in disease states such as Parkinson's disease (PD), coupled with new insights into the mechanisms of cell death and new findings from therapeutic clinical trials, are being translated into clinical practice. Although levodopa (L-Dopa) remains the most effective drug in the symptomatic treatment of PD, the emergence of side effects, particularly motor fluctuations and dyskinesias, limits its usefulness. Therefore, many parkinsonologists now advocate therapeutic strategies designed to delay the onset of L-Dopa therapy to delay the onset of L-Dopa-related motor complications. The therapeutic approach to PD, however, must be individualized and based on factors such as age of the patient, stage of the disease, and degree of interference of the symptoms with social and occupational functioning, associated symptoms such as cognitive impairment, and response to treatment. This review summarizes the current therapeutic strategies, but it is important to emphasize that the treatment recommendations must be tailored to the needs of individual patients.

Effects of oligonucleotide antisense to dopamine D(1A) receptor messenger RNA in a rodent model of levodopa-induced dyskinesia

Dyskinesias are abnormal involuntary movements which develop as a side-effect of long-term treatment with levodopa in patients with Parkinson's disease. The pathophysiology underlying these dyskinesias remains unclear, although, it has been suggested that heightened activity of dopamine D(1) receptor-bearing striatonigral neurons may play a key role. Chronic pulsatile levodopa administration to hemiparkinsonian rats results in sensitization of rotational responses to apomorphine. This sensitization is thought to be analogous to levodopa-induced dyskinesias in humans. In these studies, we further clarify the role of the dopamine D(1A) receptor in this rodent model of levodopa-induced dyskinesias using an in vivo oligonucleotide antisense approach. Hemiparkinsonian rats received twice daily injections of levodopa for three weeks followed by intrastriatal infusion of dopamine D(1A) receptor antisense (7nmol/day, three days), a scrambled missense control sequence, or saline. Those animals treated with antisense displayed significantly fewer apomorphine-induced rotations than saline- or missense-treated controls.By reducing dopamine D(1A) receptor expression, we were able to attenuate sensitization of the response to apomorphine resulting from chronic pulsatile levodopa treatment. Thus, the dopamine D(1A) receptor appears to play a significant role in levodopa-induced dyskinesias and warrants further examination. These findings may have important implications for the development of selective treatment strategies designed to alleviate parkinsonian symptoms, while minimizing motor complications.

Antidyskinetic effect of JL-18, a clozapine analog, in parkinsonian monkeys

Clozapine reduces L-3,4-dihydroxyphenylalanine (L-Dopa)-induced dyskinesias in parkinsonian patients. To test if the antidyskinetic effect of clozapine is related to antagonism at the dopamine D(4) receptor, we investigated the effect of 8-methyl-6-(4-methyl-1-piperazinyl)-11H-pyrido[2,3-b][1, 4]benzodiazepine (JL-18), a structural analog of clozapine which is more selective for this receptor. Four 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP)-treated cynomolgus monkeys with a stable parkinsonian syndrome and reproducible dyskinesias to L-Dopa were used in this study. They were injected subcutaneously (s.c.) with L-Dopa methyl ester (125 mg per animal) plus benserazide (50 mg per animal; L-Dopa/benserazide) alone or in combination with JL-18 (at the doses of 0.1, 0.3, or 0.9 mg/kg, s.c.). Subcutaneous injection of sterile saline was used as control. L-Dopa/benserazide increased locomotion and improved parkinsonism but also induced dyskinesias. Co-administration of JL-18, at low doses (0.1, 0.3 mg/kg) with L-Dopa/benserazide, produced a dose-dependent reduction in L-Dopa-induced dyskinesias without a parallel return to parkinsonism. The present results suggest that novel selective dopamine D(4) receptor antagonists may represent a useful tool to reduce L-Dopa-induced dyskinesias.

Dopamine agonists: what is the place of the newer compounds in the treatment of Parkinson's disease?

Three new dopamine agonists (cabergoline, pramipexole, ropinirole) have been put on to the market within the past months to treat patients with Parkinson's disease. Like any marketed dopamine agonists, the new compounds bind to the D2-like receptors. Pramipexole and ropinirole appear to be quite close drugs. Both are selective non ergot D2 (and preferentially D3) agonists, with an elimination half-life of 5 to 10 hours. Conversely, cabergoline is an ergot derivative, less selective for the D2 receptors, with a much longer elimination half-life (60 hours or more). In moderately advanced levodopa treated patients with Parkinson's disease and motor fluctuations, cabergoline, pramipexole and ropinirole all do significantly better than placebo in reducing UPDRS motor examination scores, time spent off and daily dose of levodopa. None of the 3 newer agonists proved to do significantly better than bromocriptine in this indication, at the cost of very similar adverse effects. In de novo levodopa naive patients, pramipexole and ropinirole did significantly better than placebo in short-term (few months) follow-up trials, at the cost again of classical dopaminergic adverse effects. Ropinirole was marginally more effective than bromocriptine, while its use induced the same risk of psychosis than the "old" reference agonist. Early treatment with cabergoline, compared with levodopa, in a long-term (5 year) study reduced the relative risk of developping motor complication by more than 50%. A similar study is presently on-going to compare ropinirole and levodopa. Clinical trials to assess putative neuroprotective effects are also on going with ropinirole and pramipexole. Up to now, the available clinical controlled data suggest that the newer dopamine agonists have very similar clinical effects with only minor superiority, if any, versus bromocriptine.

Treating and preventing levodopa-induced dyskinesias: current and future strategies

Prevention of levodopa-induced dyskinesias is a therapeutic challenge for physicians. At present, it seems only possible to delay dyskinesias and motor fluctuations. In younger patients (aged <50 years), the strategy is to use a dopamine D2 agonist as monotherapy and then to add levodopa treatment when the parkinsonian symptoms progress. In older patients, (aged >50 years to <70 years), the therapeutic approach is to use early combination therapy of levodopa and a D2 agonist. The treatment of levodopa-induced dyskinesias must be considered in regard to the subtype and the severity of dyskinesias, and the patient. The general approach to the treatment of peak dose dyskinesias is to maintain dopamine brain stimulation at as stable a level as possible by keeping plasma and brain levodopa concentrations in the therapeutic range (above the therapeutic threshold but below the dyskinesia threshold). An appropriate strategy is to reduce the individual dose of levodopa, to spread out the daily levodopa dose and/or to try treatment with the sustained-release form of the drug. Combination treatment with the standard and sustained-release levodopa formulations is also possible. Stopping selegiline (deprenyl) therapy may reduce dyskinesias; reducing the dose of, or stopping treatment with, a dopamine agonist may also be beneficial. Anti-dyskinetic drugs such as amantadine, buspirone, fluoxetine, propanolol and principally clozapine may be used. In severe dyskinesias, apomorphine infusion may be tried. In refractory dyskinesia, surgical procedures such as pallidotomy and chronic deep brain stimulation (globus pallidus/subthalamic nucleus) may be proposed. Theoretically, treatment of diphasic dyskinesias requires the maintenance of plasma levodopa concentrations above the dyskinesia threshold. However, this approach leads to constant and severe dyskinesia after only a few weeks of treatment. Thus, the strategy used to treat diphasic dyskinesia is close to the treatment of peak-dose dyskinesias. Apomorphine (or the liquid form of levodopa) may be helpful to prevent diphasic dyskinesias. In selected patients, a midday rest in the 'off' phase may decrease the duration of dyskinesia. Treatment of early morning dystonia is based on the addition to the regimen of the sustained release formulation of levodopa before bedtime. Liquid levodopa and apomorphine injection may be used just before the appearance of the dystonic posture. Botulinum toxin may be helpful in severe dystonia.

D1 receptor blockade improves L-dopa-induced dyskinesia but worsens parkinsonism in MPTP monkeys

OBJECTIVE

To determine whether dopamine (DA) D1 or DA D2 receptors are associated predominantly with the antiparkinsonian versus the dyskinetic effect of levodopa.

METHODS

The authors used four L-dopa-primed, dyskinetic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-exposed monkeys to test whether acute and selective blockade of the DA D1 receptor subtype, using SCH 23390 and NNC 01-112, could reduce L-dopa-induced dyskinesias without altering the relief of symptoms. Blockade of DA receptors using sulpiride (D2) and clozapine (D1-D2-like) was studied for comparison.

RESULTS

With the notable exception of the lowest dose of clozapine tested, coadministration of DA D1 or D2 antidopaminergic agents with L-dopa reduced the L-dopa-induced dyskinesias but also caused a return of parkinsonian disability. Prolonged latencies from intake of a single oral dose of L-dopa to turning "on," decreased duration of the "on" state, and a complete failure to induce benefit was also observed.

CONCLUSION

Low-dose clozapine could be an effective adjunct to reduce L-dopa-induced dyskinesias without altering the relief of parkinsonian symptoms. Interactions with many neurotransmitter systems may explain the better pharmacologic profile of clozapine, including DA D4 (rather than D1), serotonin, acetylcholine, and noradrenaline. Neither dyskinesias nor antiparkinsonian effects can be ascribed solely to the D2 or D1 receptor. Thus, some cooperation between the two receptors appears necessary for these behavioral effects.

Parkinson's disease. Second of two parts

At no time in the past have the basic and clinical sciences applied to Parkinson's disease been so active. Experimental therapies under study at present promise to improve on the limitations of existing treatments. Future progress in understanding the causation and pathogenesis of the disorder will permit the development of new treatments that will slow, halt, or even reverse the currently inexorable progressive course of Parkinson's disease.

Clozapine use in Parkinson's disease: a retrospective analysis of a large multicentered clinical experience

We conducted a multicentered, retrospective review of clozapine's (CZP) effects on a range of psychiatric, sleep, cognitive, motor, and sensory disorders in Parkinson's disease (PD). Therapeutic outcomes and adverse events were compared with varying prescribing practices at participating sites. The medical records of 172 consecutive PD patients treated with CZP at four movement disorder clinics were reviewed. Low-dose CZP improved psychiatric symptoms of psychosis, anxiety, depression, hypersexuality, sleep disturbance, and akathisia. Tremor, torticollis, limb dystonia, and pain showed modest rates of improvement. Twenty-three percent of patients withdrew as a result of adverse events or treatment failure. Inpatient CZP initiation did not improve therapeutic efficacy, or reduce adverse events or the withdrawal rate. Low-dose CZP in the outpatient setting is generally an effective and well-tolerated treatment for many of the psychiatric, sleep, motor, and sensory disturbances common to late-stage PD.

Low dosage clozapine effects on L-dopa induced dyskinesias in parkinsonian patients

OBJECTIVES

The aim of this study was to investigate the clinical efficacy of clozapine, an atypical neuroleptic, on L-dopa induced dyskinesias of Parkinson's disease.

MATERIAL AND METHODS

In an open study, a group of 10 PD patients was treated with low dosage clozapine (mean 30 mg/day) for a 4-month period and L-dopa dyskinesias were evaluated in basal conditions and during clozapine treatment after the usual morning dose of clozapine. We utilized the AIMS for evaluation of dyskinesias and UPDRS for the assessment of motor performances.

RESULTS

Clozapine produced a significant (P<0.05) reduction of dyskinesias 1 week after the therapy onset. This effect was more pronounced at the end of the 2nd week and remained stable through the following months. We did not observe significant variations of motor performances.

CONCLUSION

A low dose of clozapine appears to be beneficial for patients with L-dopa induced dyskinesias that do not respond to other drugs and therapeutic measures.

P450 enzymes and Parkinson's disease: the story so far

Environmental or endogenous toxins may cause nigral cell death in Parkinson's disease (PD) as a result of genetic susceptibility conferred by altered expression of P450 enzymes. Attention over the last 10 years has focused on CYP2D6 polymorphisms and susceptibility to PD. This review summarizes reports arising from both phenotypic and genotypic studies involving CYP2D6 and PD. Phenotypic studies have failed to support a link between CYP2D6 and PD. The more powerful genetic studies initially indicated a link between CYP2D6B mutations and PD, but critical analysis of the literature and recent studies emerging from independent laboratories fail to confirm this. Mutations in CYP2D6B are also not implicated in familial PD. As yet, there is no conclusive evidence to suggest that CYP2D6 polymorphisms confer susceptibility to PD. Whether polymorphisms in other P450s (for example, CYP1A1 and CYP2E1) are implicated in PD remains to be established.

The emerging role of clozapine in the treatment of movement disorders

Clozapine, the only commercially available atypical neuroleptic, is approved for the treatment of schizophrenic patients who are unresponsive to or intolerant of typical neuroleptics. It has an unusual pharmacologic profile compared with standard neuroleptics, and it follows that clinical response to this drug is also different. It has shattered the notion that a drug must be capable of inducing or worsening parkinsonism to be a potent antipsychotic. Based on these findings, it is being used increasingly by neurologists for psychiatric and nonpsychiatric problems in patients with movement disorders. The most common use for clozapine among neurologists is in the management of drug-induced psychosis in Parkinson's disease (PD). This problem has been a source of increased morbidity and mortality in PD because of a lack of adequate therapeutic intervention. At this time, because of success in numerous open trials, with improvement of > 80% of patients, clozapine therapy for psychosis in PD is becoming the standard of care. It also appears to be of value in the management of some motor features of PD, including tremors and dyskinesia and possibly even sensory symptoms such as akathisia and pain. The literature also suggests that clozapine may be of potential benefit in hyperkinetic movement disorders including essential tremor, Huntington's disease, and tardive dyskinesia. We review the current data concerning the use of clozapine in patients with these movement disorders and others.

A treatment for tardive dyskinesia and some other extrapyramidal symptoms

The effects of the administration of acetazolamide and thiamine (A + T) on the symptoms of tardive dyskinesia (TD) and parkinsonism of 8 elderly and 25 younger chronic hospitalized mental patients were examined in a placebo-controlled, double-blind, counterbalanced two-period cross-over study with initial baselines and intervening washout periods. All patients were maintained on their prestudy psychoactive and anti-Parkinson medications, without alteration, throughout the study. The elderly group received 1.5 g acetazolamide and thiamine per day in three divided doses for 3 weeks. The younger group received 1.5 g thiamine and 2.0 g acetazolamide per day in divided doses for 2 months. Both groups showed a significant decrease in scores on the Abnormal Involuntary Movement Scale (TD) and the Simpson-Angus Neurological Rating Scale (parkinsonism) while on A + T. The A + T effects were unrelated to age, gender, diagnosis, or maintenance medications.

Neuropsychiatric adverse effects of antiparkinsonian drugs. Characteristics, evaluation and treatment

Parkinson's disease (PD) is a progressive neurological condition that causes considerable disability in the elderly. Drugs used to treat PD, such as levodopa, offer symptomatic relief but often have neuropsychiatric adverse effects, most prominently psychosis and delirium. Aged patients and those with dementia are particularly vulnerable to these adverse effects. Evaluating PD patients with drug-induced neuropsychiatric adverse effects is made difficult by their complex clinical presentations. The treatment of drug-induced psychosis and delirium begins with manipulating the antiparkinsonian drug regimen, but this frequently worsens motor function. Atypical antipsychotics such as clozapine have been successfully employed to treat the psychosis without worsening the motor disability. Patient intolerance of clozapine therapy has prompted open-label studies with newer agents such as risperidone, remoxipride, zotepine, mianserin and ondansetron.

Effects of L-DOPA-therapy on dopamine D2 receptor mRNA expression in the striatum of MPTP-intoxicated parkinsonian monkeys

The cellular expression of dopamine D2 receptor mRNA was examined in striatal (caudate nucleus and putamen) neurones of 9 Macaca fascicularis monkeys rendered parkinsonian by systemic injection of MPTP. Messenger RNA abundance was determined by quantitative in situ hybridization using human-specific 35S-labelled oligonucleotides. Control monkeys were untreated and received neither MPTP nor L-DOPA while the rest were rendered parkinsonian and received chronic levodopa therapy to induce dyskinesia. In the control brains a strong dopamine D2 receptor hybridization signal was detected overlying medium-sized and some large neurons in both the caudate nucleus and putamen. Neurons from the lateral and medial regions of the caudate nucleus, and from the dorsal and ventral regions of the putamen were analysed separately. A significant increase in the cellular abundance of dopamine D2 receptor mRNA was seen in the striatum of MPTP-treated monkeys; this increase being restricted to the population of medium-sized striatal cells. No such increase in dopamine D2 receptor mRNA was observed in (dyskinetic) L-DOPA-treated monkeys suggesting that levodopa-therapy normalises D2 receptor expression in post-synaptic striatal cells. The cellular abundance of dopamine D2 receptor mRNA expressed by large striatal neurons (putative cholinergic cells) was unaffected by either MPTP treatment or levodopa therapy. The implications of these findings for the development of levodopa-induced dyskinesias is discussed.

Clozapine for the treatment of psychosis in Parkinson's disease: a review

The occurrence of psychosis is frequent during the evolution of Parkinson's disease. The reduction of therapeutics or the use of classical neuroleptics may improve the symptoms, but usually worsens parkinsonism. Clozapine is an atypical neuroleptic with only few extrapyramidal effects, which has been proposed at low dose in this indication since 1985. A review of the literature, about more than 200 patients shows good results in approximately 90% without worsening of extrapyramidal symptoms. Some patients even noted an improvement of their motor state while treated by clozapine alone or as dopatherapy was secondarily increased. More controversial results were obtained in demented or depressed patients. Sedation is one of the most frequently encountered side-effect but rarely necessitates the withdrawal of clozapine. Even if the risk of agranulocytosis is slight, regular blood cell counts must be done.

Is striatal dopaminergic receptor imbalance responsible for levodopa-induced dyskinesia?

Abnormal involuntary movements (dyskinesias) of variable intensity eventually emerge in the majority of Parkinson's disease patients chronically treated with standard oral levodopa. They create social and physical embarrassment and narrow the therapeutic options normally proposed to improve Parkinsonian symptoms. Thus far, indirect clinical and experimental evidence has implicated the potential role of dopamine D1 receptor activation in the generation of dopa dyskinesia. In recent years, our group has tested several dopaminergic agonists of variable half-life and selectivity in monkeys rendered parkinsonian following toxic exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). These monkeys readily develop dyskinesia when treated with levodopa and provide the best animal model to study this complication. Our results in "drug-naive" and "dyskinesia-primed" MPTP animals suggest that pathological sensitisation of D2 receptor-mediated striatal outflow is necessary and sufficient for the induction of dopa dyskinesia, with perhaps a synergistic contribution from D1 receptors, and that repeated short-lived stimulation is important in the sensitisation process. This model supports the hypothesis that more continuous forms of dopaminomimetic therapy represent the best therapeutic approach for Parkinson's disease and calls for the development of novel D1 agonists for further clinical testing.