Combined beneficial effect of rasagiline on motor function and depression in de novo PD

Dissociable effects of dopaminergic medications on depression symptom dimensions in Parkinson disease

Depression in Parkinson disease (PD) is common, is disabling and responds poorly to standard antidepressants. Motivational symptoms of depression are particularly prevalent in PD and emerge with loss of dopaminergic innervation of the striatum. Optimizing dopaminergic treatment for PD can improve depressive symptoms. However, the differential effect of antiparkinsonian medication on symptom dimensions of depression is not known. Using data from a large (n = 412) longitudinal study of patients with newly diagnosed PD followed over 5 years, we investigated whether there are dissociable effects of dopaminergic medications on different depression symptom dimensions in PD. Previously validated 'motivation' and 'depression' dimensions were derived from the 15-item geriatric depression scale. Dopaminergic neurodegeneration was measured using repeated striatal dopamine transporter imaging. We identified dissociable associations between dopaminergic medications and different dimensions of depression in PD. Dopamine agonists were shown to be effective for treatment of motivational symptoms of depression. In contrast, monoamine oxidase-B inhibitors improved both depressive and motivation symptoms, albeit the latter effect is attenuated in patients with more severe striatal dopaminergic neurodegeneration.

Dissociable effects of dopaminergic medications on depression symptom dimensions in Parkinson's disease

Background

Depression in Parkinson's disease (PD) is common, disabling and responds poorly to standard antidepressant medication. Motivational symptoms of depression, such as apathy and anhedonia, are particularly prevalent in depression in PD and predict poor response to antidepressant treatment. Loss of dopaminergic innervation of the striatum is associated with emergence of motivational symptoms in PD, and mood fluctuations correlate with dopamine availability. Accordingly, optimising dopaminergic treatment for PD can improve depressive symptoms, and dopamine agonists have shown promising effects in improving apathy. However, the differential effect of antiparkinsonian medication on symptom dimensions of depression is not known.

Aims

We hypothesised that there would be dissociable effects of dopaminergic medications on different depression symptom dimensions. We predicted that dopaminergic medication would specifically improve motivational symptoms, but not other symptoms, of depression. We also hypothesised that antidepressant effects of dopaminergic medications with mechanisms of action reliant on pre-synaptic dopamine neuron integrity would attenuate as pre-synaptic dopaminergic neurodegeneration progresses.

Methods

We analysed data from a longitudinal study of 412 newly diagnosed PD patients followed over five years in the Parkinson's Progression Markers Initiative cohort. Medication state for individual classes of Parkinson's medications was recorded annually. Previously validated "motivation" and "depression" dimensions were derived from the 15-item geriatric depression scale. Dopaminergic neurodegeneration was measured using repeated striatal dopamine transporter (DAT) imaging.

Results

Linear mixed-effects modelling was performed across all simultaneously acquired data points. Dopamine agonist use was associated with relatively fewer motivation symptoms as time progressed (interaction: β=-0.07, 95%CI [-0.13,-0.01], p=0.015) but had no effect on the depression symptom dimension (p=0.6). In contrast, monoamine oxidase-B (MAO-B) inhibitor use was associated with relatively fewer depression symptoms across all years (β=-0.41, 95%CI [-0.81,-0.01], p=0.047). No associations were observed between either depression or motivation symptoms and levodopa or amantadine use. There was a significant interaction between striatal DAT binding and MAO-B inhibitor use on motivation symptoms: MAO-B inhibitor use was associated with lower motivation symptoms in patients with higher striatal DAT binding (interaction: β=-0.24, 95%CI [-0.43, -0.05], p=0.012). No other medication effects were moderated by striatal DAT binding measures.

Conclusions

We identified dissociable associations between dopaminergic medications and different dimensions of depression in PD. Dopamine agonists may be effective for treatment of motivational symptoms of depression. In contrast, MAO-B inhibitors may improve both depressive and motivation symptoms, albeit the latter effect appears to be attenuated in patients with more severe striatal dopaminergic neurodegeneration, which may be a consequence of dependence on pre-synaptic dopaminergic neuron integrity.

Neurobiology of depression in Parkinson's disease: Insights into epidemiology, molecular mechanisms and treatment strategies

Parkinson's disease (PD) is characterized mainly by motor dysfunctions due to the progressive loss of dopaminergic neurons. However, PD patients experience a multitude of debilitating non-motor symptoms, including depression, which may have deleteriously detrimental effects on life. Depression is multifactorial and exhibits a bimodal progression in PD, but its underlying molecular mechanisms are poorly understood. Studies demonstrating the pathophysiology of depression in PD and the specific treatment strategies for depression-like symptoms in PD patients are largely lacking, often underrated, under-recognized and, consequently, inadequately/under-treated. Nevertheless, reports suggest that the incidence of depression is approximately 20-30% of PD patients and may precede the onset of motor symptoms. Diagnosing depression in PD becomes difficult due to the clinical overlap in symptomatology between the two diseases, and the nigrostriatal dysfunction alone is insufficient to explain depressive symptoms in PD. Therefore, the current study provides an overview of the molecular mechanisms underlying the development of depression in PD and new insights into developing current antidepressant strategies to treat depression in PD. This review will identify and understand the molecular pathological mechanisms of depression in PD that will fundamentally help tailoring therapeutic interventions for depressive symptoms in PD.

Switching from Rasagiline to Safinamide as an Add-On Therapy Regimen in Patients with Levodopa: A Literature Review

Parkinson's disease (PD) is a complex disease, and the treatment is focused on the patient's clinical symptoms. Levodopa continues to be the most effective drug for symptomatic PD treatment. However, chronic levodopa treatment is associated with the development of motor complications in most patients. Add-on therapeutic drugs, such as dopamine agonists and monoamine oxidase B (MAO-B) inhibitors, for example, safinamide and rasagiline, may be a desirable addition to continuously increase the levodopa dose for the optimization of motor control in PD. The scientific literature shows that safinamide significantly alleviated motor fluctuations with no increase in troublesome dyskinesia, thanks to its unique double mechanism, providing further benefits to fluctuating PD patients when compared to a placebo or other drugs. Switching from rasagiline to safinamide has been shown to improve the wearing-off phenomena, which is defined as the recurrent, predictable worsening of symptoms of parkinsonism at the end of the levodopa dose until the next dose reaches a clinical effect. In this situation, safinamide may be helpful for reducing the total daily dose of levodopa, improving the OFF time and ON time without troublesome dyskinesias, and being more effective than other MAO-B inhibitors. In this narrative review, we explore the switch from rasagiline to safinamide in patients with motor complications as a feasible and effective alternative to optimize antiparkinsonian treatment.

Comparative efficacy and acceptability of drug treatments for Parkinson's disease with depression: A systematic review with network meta-analysis

Depressive symptom is the prevailing non-motor symptom of Parkinson's disease (PD). Drug treatments for depressed PD (dPD) can mitigate the symptoms of patients. However, the results are discordant and need further analysis. This systematic review with network meta-analysis aims to evaluate the drug treatments for dPD. We included double-blind, randomized controlled trials to compare antidepressants with placebo or other antidepressants in dPD. We performed traditional pairwise analysis and network meta-analysis concerning the efficacy, acceptability, depression score, and adverse effect. The surface under the cumulative ranking curve was to assess the ranking probabilities of the enrolled agents. We enrolled 62 studies, including 12,353 subjects, to analyze these estimates. For the traditional pairwise meta-analysis, dopamine agonist (DOP; OR = 2.20 [95% CI, 1.46 to 3.33]) and selective serotonin reuptake inhibitor (SSRI; OR = 2.30 [95% CI, 1.15 to 4.60]) were observed to improve the efficacy compared with placebo. For network meta-analysis, DOP was observed to improve the efficacy compared with placebo (OR = -0.84 [95% CI, -1.20 to -0.48]). Both direct and indirect evidence showed that several treatments, e.g., DOP, monoamine-oxidase inhibitor, serotonin-norepinephrine reuptake inhibitors, SSRI, and tricyclic antidepressants, significantly improved depressive symptoms. DOP and SSRI had good efficacy and improved symptoms considerably in dPD, but the adverse effect of these agents was needed to follow closely.

Rasagiline Withdrawal Syndrome in Parkinson’s Disease

Parkinson’s disease (PD) patients using dopamine agonists can develop withdrawal symptoms, referred to as dopamine agonist withdrawal syndrome (DAWS), under dose tapering or discontinuation of these drugs. DAWS includes a severe stereotypical cluster of psychiatric and psychological symptoms encompassing severe mood and anxiety disturbances, autonomic symptoms, as well as generalized pain and drug cravings. However, symptoms of withdrawal of dopamine replacement therapies (DRT) are not simply limited to dopamine agonists tapering, as observed in PD patients on deep brain stimulation after dopaminergic drugs withdrawal related to surgery. To date, no DRT-related withdrawal syndrome has been described in PD patients who discontinue rasagiline, an irreversible inhibitor of monoamine oxidase-B (MAO-B). Here we report three PD patients who developed a severe withdrawal syndrome after rasagiline suspension. The syndrome was mainly characterized by prominent psychiatric disorders (depression, anxiety with panic attacks, dysphoria, and agitation) associated with fatigue, generalized pain, and autonomic manifestations (closely resembling symptoms of DAWS). In our opinion, this report suggests the importance of closely monitoring PD patients undergoing rasagiline suspension for withdrawal symptoms and provides interesting points of reflection on the role of rasagiline and other MAO-B inhibitors in mood disorders.

Antidepressant-Like Properties of Intrastriatal Botulinum Neurotoxin-A Injection in a Unilateral 6-OHDA Rat Model of Parkinson's Disease

Parkinson’s patients often suffer from depression and anxiety, for which there are no optimal treatments. Hemiparkinsonian (hemi-PD) rats were used to test whether intrastriatal Botulinum neurotoxin-A (BoNT-A) application could also have antidepressant-like properties in addition to the known improvement of motor performance. To quantify depression- and anxiety-like behavior, the forced swim test, tail suspension test, open field test, and elevated plus maze test were applied to hemi-PD rats injected with BoNT-A or vehicle. Furthermore, we correlated the results in the forced swim test, open field test, and elevated plus maze test with the rotational behavior induced by apomorphine and amphetamine. Hemi-PD rats did not show significant anxiety-like behavior as compared with Sham 6-OHDA- + Sham BoNT-A-injected as well as with non-injected rats. However, hemi-PD rats demonstrated increased depression-like behaviors compared with Sham- or non-injected rats; this was seen by increased struggling frequency and increased immobility frequency. Hemi-PD rats intrastriatally injected with BoNT-A exhibited reduced depression-like behavior compared with the respective vehicle-receiving hemi-PD animals. The significant effects of intrastriatally applied BoNT-A seen in the forced swim test are reminiscent of those found after various antidepressant drug therapies. Our data correspond with the efficacy of BoNT-A treatment of glabellar frown lines in treating patients with major depression and suggest that also intrastriatal injected BoNT-A may have some antidepressant-like effect on hemi-PD.

Impact of SAfinamide on Depressive Symptoms in Parkinson's Disease Patients (SADness-PD Study): A Multicenter Retrospective Study

BACKGROUND

We aimed to assess the effects of safinamide on depression, motor symptoms, and the serotonin syndrome related to its co-administration with antidepressants in patients with Parkinson's disease (PD).

METHODS

We retrospectively analyzed the data of patients at 1 and 3 months of follow-up compared to baseline.

RESULTS

n = 82 (safinamide 50 mg = 22, 100 mg = 60, with antidepressants = 44). First, we found improvement in depression (Hamilton Depression Rating Scale: -6 ± 5.10 at 1 month and -7.27 ± 5.10 at 3 months, p < 0.0001; Patient Global Impression of Improvement Scale: 60.3% and 69.5% of patients at 1 and 3 months reported some improvement). Second, safinamide improved the daily life activities and motor symptoms/motor complications (Unified Parkinson's Disease Rating Scale (UPDRS-II): -2.51 ± 6.30 and -2.47 ± 6.11 at 1 and 3 months, p < 0.0001; III: -3.58 ± 8.68 and -4.03 ± 8.95 at 1 and 3 months, p < 0.0001; IV: -0.61 ± 2.61 and -0.8 ± 2.53 at 1 and 3 months, p < 0.0001). Third, 7.31% and 8.53% of patients developed non-severe adverse events related to safinamide at 1 and 3 months. Serotonin syndrome was not observed in the patients treated with antidepressants; some isolated serotonin syndrome symptoms were reported.

CONCLUSIONS

Safinamide could be useful for treating depression in PD; it was effective for motor symptoms and motor complications and safe even when co-administered with antidepressants.

Monoamine Oxidase Inhibitors: From Classic to New Clinical Approaches

Monoamine oxidases (MAOs) are involved in the oxidative deamination of different amines and neurotransmitters. This pointed them as potential targets for several disorders and along the last 70 years a wide variety of MAO inhibitors have been developed as successful drugs for the treatment of complex diseases, being the first drugs approved for depression in the late 1950s. The discovery of two MAO isozymes (MAO-A and B) with different substrate selectivity and tissue expression patterns led to novel therapeutic approaches and to the development of new classes of inhibitors, such as selective irreversible and reversible MAO-B inhibitors and reversible MAO-A inhibitors. Significantly, MAO-B inhibitors constitute a widely studied group of compounds, some of them approved for the treatment of Parkinson's disease. Further applications are under development for the treatment of Alzheimer's disease, amyotrophic lateral sclerosis, and cardiovascular diseases, among others. This review summarizes the most important aspects regarding the development and clinical use of MAO inhibitors, going through mechanistic and structural details, new indications, and future perspectives. Monoamine oxidases (MAOs) catalyze the oxidative deamination of different amines and neurotransmitters. The two different isozymes, MAO-A and MAO-B, are located at the outer mitochondrial membrane in different tissues. The enzymatic reaction involves formation of the corresponding aldehyde and releasing hydrogen peroxide (H₂O₂) and ammonia or a substituted amine depending on the substrate. MAO's role in neurotransmitter metabolism made them targets for major depression and Parkinson's disease, among other neurodegenerative diseases. Currently, these compounds are being studied for other diseases such as cardiovascular ones.

Treatment of Parkinson's Disease by MAO-B Inhibitors, New Therapies and Future Challenges - A Mini-Review

BACKGROUND

One of the most prevalent neurodegenerative diseases with increasing age is Parkinson's disease (PD). Its pathogenesis is unclear and mainly confined to glutamate toxicity and oxidative stress. The dyskinesia and motor fluctuations and neuroprotective potential are the major concerns which are still unmet in PD therapy.

OBJECTIVE

This article is a capsulization of the role of MAO-B in the treatment of PD, pharmacological properties, safety and efficiency, clinical evidence through random trials, future therapies and challenges.

CONCLUSION

MAO-B inhibitors are well tolerated for the treatment of PD because of their pharmacokinetic properties and neuroprotective action. Rasagiline and selegiline were recommended molecules for early PD and proven safe and provide a modest to significant rise in motor function, delay the use of levodopa and used in early PD. Moreover, safinamide is antiglutamatergic in action. When added to Levodopa, these molecules significantly reduce the offtime with a considerable improvement of non-motor symptoms. This review also discusses the new approaches in therapy like the use of biomarkers, neurorestorative growth factors, gene therapy, neuroimaging, neural transplantation, and nanotechnology. Clinical evidence illustrated that MAOB inhibitors are recommended as monotherapy and added on therapy to levodopa. A large study and further evidence are required in the field of future therapies to unwind the complexity of the disease.

Antidepressant-Like Effect of β-Lactolin, a Glycine-Threonine-Tryptophan-Tyrosine Peptide

The number of patients with mental illnesses, including depression, is rapidly increasing, and daily lifestyle is closely associated with the development of symptoms. Consequently, corrective measures, such as diet-based treatment for diseases, are receiving great attention. We previously showed that β-lactolin, a β-lactopeptide of glycine-threonine-tryptophan-tyrosine peptide, inhibits monoamine oxidase and improves memory impairment in mice, but the effects on depression have not been investigated. Here we showed that β-lactolin improved depression-like behavior via dopamine-D1-like receptor. Orally administered β-lactolin reduced immobility time in tail suspension test (TST). Pretreatment with SCH23390, dopamine D1-like receptor antagonist, attenuated the reduction in TST by β-lactolin. These effects were observed by the treatment with whey digest rich in β-lactolin. In addition, β-lactolin increased the levels of dopamine in the frontal cortex associated with the depression-like behavior. The present study suggests that supplements or nutraceutical compounds in whey digests (such as β-lactolin) show antidepressant-like effect.

Update on treatments for nonmotor symptoms of Parkinson's disease-an evidence-based medicine review

OBJECTIVE

To update evidence-based medicine recommendations for treating nonmotor symptoms in Parkinson's disease (PD).

BACKGROUND

The International Parkinson and Movement Disorder Society Evidence-Based Medicine Committee's recommendations for treatments of PD were first published in 2002, updated in 2011, and now updated again through December 31, 2016.

METHODS

Level I studies testing pharmacological, surgical, or nonpharmacological interventions for the treatment of nonmotor symptoms in PD were reviewed. Criteria for inclusion and quality scoring were as previously reported. The disorders covered were a range of neuropsychiatric symptoms, autonomic dysfunction, disorders of sleep and wakefulness, pain, fatigue, impaired olfaction, and ophthalmologic dysfunction. Clinical efficacy, implications for clinical practice, and safety conclusions are reported.

RESULTS

A total of 37 new studies qualified for review. There were no randomized controlled trials that met inclusion criteria for the treatment of anxiety disorders, rapid eye movement sleep behavior disorder, excessive sweating, impaired olfaction, or ophthalmologic dysfunction. We identified clinically useful or possibly useful interventions for the treatment of depression, apathy, impulse control and related disorders, dementia, psychosis, insomnia, daytime sleepiness, drooling, orthostatic hypotension, gastrointestinal dysfunction, urinary dysfunction, erectile dysfunction, fatigue, and pain. There were no clinically useful interventions identified to treat non-dementia-level cognitive impairment.

CONCLUSIONS

The evidence base for treating a range of nonmotor symptoms in PD has grown substantially in recent years. However, treatment options overall remain limited given the high prevalence and adverse impact of these disorders, so the development and testing of new treatments for nonmotor symptoms in PD remains a top priority. © 2019 International Parkinson and Movement Disorder Society.

An Investigation on the Clinical Features and Neurochemical Changes in Parkinson's Disease With Depression

Objective: To investigate the clinical features and neurochemical changes in Parkinson's disease with depression (PD-D). Methods: A total of 478 PD patients were divided into PD-D and PD patients without depression (PD-ND) groups according to the 24-item Hamilton Depression Rating Scale (HAMD) score. Demographic variables, motor and non-motor symptoms and activities of daily living were evaluated. The independent influencing factors of PD-D were investigated via binary logistic regression analysis. The levels of neurotransmitters in cerebrospinal fluid (CSF) were measured and their correlations with HAMD score were analyzed. Results: The proportion of PD-D was 59.0%, of which 76.95, 20.92, and 2.13% had mild, moderate, and severe depression, respectively. Anxiety/somatization was the most prevalent sub-factor of HAMD in PD-D. The scores of UPDRS III, postural instability/gait difficulty (PIGD) type and the scores of 14-item Hamilton Anxiety Scale (HAMA) and 14-item Chalder Fatigue Scale (FS) were independently associated with PD-D. The levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) were all significantly reduced in PD-D group compared with those in PD-ND group. HAMD scores were negatively correlated with the DA levels in CSF. Conclusions: PD patients have a high proportion of depression, mainly of mild and moderate levels. The profile of depression in PD population is subtly different from that of the general population. Motor symptoms, PIGD type, anxiety and fatigue are the significant influencing factors of PD-D. Compared to 5-HT, DA may play a more important role in PD-D.

Efficacy of rasagiline for the treatment of Parkinson's disease: an updated meta-analysis

OBJECTIVE

Rasagiline is a second-generation potent selective inhibitor of monoamine oxidase-B. The aim of the study was to analyze the effectiveness of rasagiline in treatment of Parkinson's disease (PD), both as monotherapy and combination therapy.

METHODS

Medline, Cochrane, EMBASE, and Google Scholar databases were searched until 9 March 2016 using the keywords: Rasagiline, Azilect, Parkinson's disease. Randomized controlled trials of patients with PD who were randomized to treatment with rasagiline or placebo were included. Outcomes were unified Parkinson's disease rating scale (UPDRS) and the three subscales.

RESULTS

Ten studies fulfilled the inclusion criteria and 2709 patients were evaluated. The overall analysis revealed a significant improvement in change of total UPDRS scores in 1 mg/day and 2 mg/day rasagiline groups compared to placebo. Significant improvement in Part I (Mentation) of UPDRS scores was observed in 1 mg/day, but not in 2 mg/day rasagiline treatment group. Part II (ADL) and Part III (Motor) subscales significantly improved with both doses of rasagiline. Both monotherapy and combination therapy significantly improved total UPDRS scores.

CONCLUSIONS

Our results confirm the efficacy of rasagiline in PD. Further studies are required to establish the optimal dose of rasagiline, as well as to determine its effectiveness in different combination therapy protocols. KEY MESSAGES Rasagiline treatment was associated with significant improvement of UPDRS scores and the scores of the subscales. Both monotherapy and combination therapy significantly improved total UPDRS scores. Effect of rasagiline on total UPDRS scores was not dose-dependent.

Dopaminergic Therapies for Non-motor Symptoms in Parkinson's Disease

Apart from the typical motor symptoms, Parkinson's disease is characterized by a wide range of different non-motor symptoms, which are highly prevalent in all stages of the disease and have an incisive influence on quality of life. Moreover, their treatment continues to be challenging. In this review, we critically summarize the evidence for the impact of dopaminergic therapies on non-motor symptoms in Parkinson's disease. We performed a PubMed search to identify relevant clinical studies that investigated the response of non-motor symptoms to dopaminergic therapy. In the domain of neuropsychiatric disturbances, there is increasing evidence that dopamine agonists can ameliorate depression or anxiety. Other neuropsychiatric symptoms such as psychosis or impulse control disorders can also be worsened or even be induced by dopaminergic agents. For the treatment of sleep disturbances, it is essential to identify different subtypes of sleep pathologies. While there is for example profound evidence for the effectiveness of dopaminergic medication for the treatment of restless legs syndrome and sleep fragmentation, evidence for an improvement of rapid eye movement sleep behavior disorder is lacking. With regard to the broad spectrum of autonomic disturbances, response to dopaminergic treatment seems to differ largely, with on the one hand, some evidence for an improvement of sexual function or sweating with dopaminergic treatment, while on the other hand, constipation can be worsened. Finally, the analysis of sensory deficits reveals that some forms of pain, in particular fluctuation-dependent dystonic pain, can be well addressed by adapting the dopaminergic therapy, while no effect has been seen so far for hyposmia or visual deficits. Moreover, the occurrence of non-motor fluctuations is gaining increased attention, as they can be specifically addressed by a more continuous dopaminergic intake. Taken together, there is evidence of a good response of some (but not all) non-motor symptoms to dopaminergic therapy, which must be individually adapted to the special spectrum of symptoms.

Inhibitors of MAO-A and MAO-B in Psychiatry and Neurology

Inhibitors of MAO-A and MAO-B are in clinical use for the treatment of psychiatric and neurological disorders respectively. Elucidation of the molecular structure of the active sites of the enzymes has enabled a precise determination of the way in which substrates and inhibitor molecules are metabolized, or inhibit metabolism of substrates, respectively. Despite the knowledge of the strong antidepressant efficacy of irreversible MAO inhibitors, their clinical use has been limited by their side effect of potentiation of the cardiovascular effects of dietary amines (“cheese effect”). A number of reversible MAO-A inhibitors which are devoid of cheese effect have been described in the literature, but only one, moclobemide, is currently in clinical use. The irreversible inhibitors of MAO-B, selegiline and rasagiline, are used clinically in treatment of Parkinson's disease, and a recently introduced reversible MAO-B inhibitor, safinamide, has also been found efficacious. Modification of the pharmacokinetic characteristics of selegiline by transdermal administration has led to the development of a new drug form for treatment of depression. The clinical potential of MAO inhibitors together with detailed knowledge of the enzyme's binding site structure should lead to future developments with these drugs.

Antidepressants in Parkinson's disease. Recommendations by the movement disorder study group of the Neurological Association of Madrid

INTRODUCTION

Although antidepressants are widely used in Parkinson's disease (PD), few well-designed studies to support their efficacy have been conducted.

DEVELOPMENT

These clinical guidelines are based on a review of the literature and the results of an AMN movement disorder study group survey.

CONCLUSIONS

Evidence suggests that nortriptyline, venlafaxine, paroxetine, and citalopram may be useful in treating depression in PD, although studies on paroxetine and citalopram yield conflicting results. In clinical practice, however, selective serotonin reuptake inhibitors are usually considered the treatment of choice. Duloxetine may be an alternative to venlafaxine, although the evidence for this is less, and venlafaxine plus mirtazapine may be useful in drug-resistant cases. Furthermore, citalopram may be indicated for the treatment of anxiety, atomoxetine for hypersomnia, trazodone and mirtazapine for insomnia and psychosis, and bupropion for apathy. In general, antidepressants are well tolerated in PD. However, clinicians should consider the anticholinergic effect of tricyclic antidepressants, the impact of serotonin-norepinephrine reuptake inhibitors on blood pressure, the extrapyramidal effects of antidepressants, and any potential interactions between monoamine oxidase B inhibitors and other antidepressants.

Rational pharmacological approaches for cognitive dysfunction and depression in Parkinson's disease

Parkinson’s disease (PD) is not a single entity but rather a heterogeneous neurodegenerative disorder. The present study aims to conduct a critical systematic review of the literature to describe the main pharmacological strategies to treat cognitive dysfunction and major depressive disorder in PD patients. We performed a search of articles cited in PubMed from 2004 to 2014 using the following MeSH terms (Medical subject headings) “Parkinson disease”; “Delirium,” “Dementia,” “Amnestic,” “Cognitive disorders,” and “Parkinson disease”; “depression,” “major depressive disorder,” “drug therapy.” We found a total of 71 studies related to pharmacological treatment in cognitive dysfunction and 279 studies for pharmacological treatment in major depressive disorder. After fulfillment of all the inclusion and exclusion criteria, 13 articles remained for cognitive dysfunction and 11 for major depressive disorder, which are presented and discussed in this study. Further research into non-motor symptoms of PD may provide insights into mechanisms of neurodegeneration, and provide better quality of life by using rational drugs.

Prevalence, clinical features and treatment of depression in Parkinson’s disease: An update

Parkinson’s disease (PD) is one of the most prevalent neurodegenerative diseases which typically affects individuals over 65 years. Although the symptomatology is predominantly motor, neuropsychiatric manifestations, e.g., depression, apathy, anxiety, and cognitive impairment occur in the course of the illness and can have a great impact on the quality of life in these patients. Parkinson’s disease is commonly comorbid with depression with prevalence rates of depression, generally higher than those reported in general population. Depression in PD is frequently underestimated and consequently undertreated, which have significant effects on the quality of life in these patients. The neurobiology of depression in PD is complex and involves alterations in dopaminergic, serotonergic, noradrenergic and possibly other neurotransmitter systems which are affected in the course of the disease. The tricyclic antidepressants and the selective serotonin reuptake inhibitors are the two classes of antidepressant drugs used for depressive symptoms in PD. Several published studies suggested that both classes are of comparable efficacy. Other serotonergic antidepressants, e.g., nefazodone and trazodone have also been of benefit. Meanwhile, there are limited data available on other drugs but these suggest a benefit from the serotonin and noradrenaline reuptake inhibitors such as mirtazapine, venlafaxine, atomoxetine and duloxetine. Some of the drugs used in symptomatic treatment of PD, e.g., the irreversible selective inhibitors of the enzyme monoamine oxidase-B, rasagiline and selegiline as well as the dopamine receptor agonist pramipexole are likely to have direct antidepressant activity independent of their motor improving action. This would make these drugs an attractive option in depressed subjects with PD. The aim of this review is to provide an updated data on the prevalence, clinical features of depression in subjects with PD. The effects of antiparkinsonian and antidepressant drugs on depressive symptoms in these patients are also discussed.

Drug therapy for Parkinson’s disease: An update

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder, affecting about 1% of the population above the age of 65. PD is characterized by a selective degeneration of the dopaminergic neurons of the substantia nigra pars compacta. This results in a marked loss of striatal dopamine and the development of the characteristic features of the disease, i.e., bradykinesia, rest tremor, rigidity, gait abnormalities and postural instability. Other types of neurons/neurotransmitters are also involved in PD, including cholinergic, serotonergic, glutamatergic, adenosine, and GABAergic neurotransmission which might have relevance to the motor, non-motor, neuropsychiatric and cognitive disturbances that occur in the course of the disease. The treatment of PD relies on replacement therapy with levodopa (L-dopa), the precursor of dopamine, in combination with a peripheral decarboxylase inhibitor (carbidopa or benserazide). The effect of L-dopa, however, declines over time together with the development of motor complications especially dyskinesia in a significant proportion of patients within 5 years of therapy. Other drugs include dopamine-receptor-agonists, catechol-O-methyltransferase inhibitors, monoamine oxidase type B (MAO-B) inhibitors, anticholinergics and adjuvant therapy with the antiviral drug and the N-methyl-D-aspartate glutamate receptor antagonist amantadine. Although, these medications can result in substantial improvements in parkinsonian symptoms, especially during the early stages of the disease, they are often not successful in advanced disease. Moreover, dopaminergic cell death continues over time, emphasizing the need for neuroprotective or neuroregenerative therapies. In recent years, research has focused on non-dopaminergic approach such as the use of A_2A receptor antagonists: istradefylline and preladenant or the calcium channel antagonist isradipine. Safinamide is a selective and reversible inhibitor of MAO-B, a glutamate receptor inhibitor as well as sodium and calcium channel blocker. Minocycline and pioglitazone are other agents which have been shown to prevent dopaminergic nigral cell loss in animal models of PD. There is also an evidence to suggest a benefit from iron chelation therapy with deferiprone and from the use of antioxidants or mitochondrial function enhancers such as creatine, alpha-lipoic acid, l-carnitine, and coenzyme Q10.

Effects of combined MAO-B inhibitors and levodopa vs. monotherapy in Parkinson's disease

Background: Prior studies report that monoamine oxidases inhibitors (MAO-I) when used as an adjunct to levodopa ameliorate motor symptoms in Parkinson’s disease (PD), but this was not tested in relation to cognitive or psychiatric measures.

Objective: Here, we tested the effects of MAO-I as an adjunct to levodopa, in comparison to levodopa or dopamine (DA) agonists alone, on various cognitive, affective and quality of life measures.

Methods: We studied three groups of subjects: healthy controls, PD patients on combined levodopa and MAO-I, and PD patients on levodopa or DA agonists only.

Results: We found that compared to monotherapy, combined MAO-I and levodopa seemed to improve cognition, including probabilistic learning, working memory and executive functions. There were no differences between the different medication regimes on deterministic learning, attention or memory recall. It was also found that MAO-I as an adjunct to levodopa improves affective measures such as depression, apathy, anxiety and quality of life. Interestingly, this enhancing effect of combined levodopa and MAO-I was more pronounced in PD patients with severe akinesia, compared to patients with severe tremor.

Conclusion: Our data are in agreement with (a) the Continuous Dopaminergic Stimulation (CDS) theory which states that continuous stimulation of the basal ganglia enhances motor, psychiatric and cognitive functions in PD patients; and/or (b) findings that MAO-I increase the bioavailability of monoamines that have beneficial effects on motor and behavioral dysfunction in PD.