Switch from selegiline to rasagiline is beneficial in patients with Parkinson's disease

Safety comparisons among monoamine oxidase inhibitors against Parkinson's disease using FDA adverse event reporting system

Monoamine oxidase B (MAO-B) inhibitors are used to control Parkinson's disease (PD). Selegiline, rasagiline, and safinamide are widely used as MAO-B inhibitors worldwide. Although these drugs inhibit MAO-B, there are pharmacological and chemical differences, such as the inhibitory activity, the non-dopaminergic properties in safinamide, and the amphetamine-like structure in selegiline. MAO-B inhibitors may differ in adverse events (AEs). However, differences in actual practical clinics are not fully investigated. A retrospective study was conducted using FAERS, the largest database of spontaneous adverse events. AE signals for MAO-B inhibitors, including selegiline, rasagiline, and safinamide, were detected using the reporting odds ratio method and compared. Hypocomplementemia, hepatic cyst, hepatic function abnormal, liver disorder and cholangitis were detected for selegiline as drug-specific signals. The amphetamine effect was not confirmed for any of the three MAO-B inhibitors. The tyramine reaction was detected as an AE signal only for rasagiline. Moreover, the REM sleep behavior disorder was not detected as an AE signal for safinamide, suggesting that non-dopaminergic effects might be beneficial. Considering the differences in AEs for MAO-B inhibitors will assist with the appropriate PD medication.

Clinical benefit of MAO-B and COMT inhibition in Parkinson's disease: practical considerations

Inhibitors of monoamine oxidase B (MAO-B) and catechol-O-methyltransferase (COMT) are major strategies to reduce levodopa degradation and thus to increase and prolong its effect in striatal dopaminergic neurotransmission in Parkinson's disease patients. While selegiline/rasagiline and tolcapone/entacapone have been available on the market for more than one decade, safinamide and opicapone have been approved in 2015 and 2016, respectively. Meanwhile, comprehensive data from several post-authorization studies have described the use and specific characteristics of the individual substances in clinical practice under real-life conditions. Here, we summarize current knowledge on both medication classes, with a focus on the added clinical value in Parkinson's disease. Furthermore, we outline practical considerations in the treatment of motor fluctuations and provide an outlook on ongoing studies with MAO-B and COMT inhibitors.

Neuroprotective Function of Rasagiline and Selegiline, Inhibitors of Type B Monoamine Oxidase, and Role of Monoamine Oxidases in Synucleinopathies

Synucleinopathies are a group of neurodegenerative disorders caused by the accumulation of toxic species of α-synuclein. The common clinical features are chronic progressive decline of motor, cognitive, behavioral, and autonomic functions. They include Parkinson’s disease, dementia with Lewy body, and multiple system atrophy. Their etiology has not been clarified and multiple pathogenic factors include oxidative stress, mitochondrial dysfunction, impaired protein degradation systems, and neuroinflammation. Current available therapy cannot prevent progressive neurodegeneration and “disease-modifying or neuroprotective” therapy has been proposed. This paper presents the molecular mechanisms of neuroprotection by the inhibitors of type B monoamine oxidase, rasagiline and selegiline. They prevent mitochondrial apoptosis, induce anti-apoptotic Bcl-2 protein family, and pro-survival brain- and glial cell line-derived neurotrophic factors. They also prevent toxic oligomerization and aggregation of α-synuclein. Monoamine oxidase is involved in neurodegeneration and neuroprotection, independently of the catalytic activity. Type A monoamine oxidases mediates rasagiline-activated signaling pathways to induce neuroprotective genes in neuronal cells. Multi-targeting propargylamine derivatives have been developed for therapy in various neurodegenerative diseases. Preclinical studies have presented neuroprotection of rasagiline and selegiline, but beneficial effects have been scarcely presented. Strategy to improve clinical trials is discussed to achieve disease-modification in synucleinopathies.

Prescription Pattern of Monoamine Oxidase B Inhibitors Combined with Levodopa: A Retrospective Observational Analysis of Italian Healthcare Administrative Databases

Background

Parkinson’s disease is still incurable, and several factors are considered when defining pharmacological therapy.

Objective

The aim of this study was to describe the prescription pattern of monoamine oxidase B inhibitors (MAO-BIs) marketed in Italy (selegiline, rasagiline, safinamide) as an add-on to levodopa among new users of MAO-BIs, from the perspective of the Italian National Health Service.

Patients and Methods

Through cross-linkage of administrative healthcare data in the Ricerca e Salute (ReS) database, adults with a supply of one or more MAO-BIs in 2017, and with no other MAO-BI use since 2013, were selected. Levodopa had to be supplied within 30 days before/after the MAO-BI. The incidence, use, sex, age, comorbidities, 2-year prescription patterns (i.e., switches, proportion of treated patients per semester/year, mean daily milligrams/monthly tablets supplied, discontinuation, change to other anti-Parkinson drug) of patients taking MAO-BIs were provided.

Results

In 2017, 1059 new users received an MAO-BI (incidence 22.6 × 100,000 adults) combined with levodopa: 502 subjects (10.7 × 100,000) were treated with selegiline, 161 (3.4 × 100,000) were treated with rasagiline, and 396 (8.4 × 100,000) were treated with safinamide. The cohorts mainly consisted of males with a median age of ≥ 74 years. Treatment incidences increased with age. Switches occurred in 18.0%, 11.0%, and 4.3% of the selegiline, rasagiline, and safinamide cohorts, respectively. Most of the patients switching from selegiline/safinamide changed to rasagiline, while most of the patients switching from rasagiline changed to safinamide. From the first to second years, patient numbers reduced by ≤ 50%, and the daily milligrams/monthly tablets slightly increased. Six-month discontinuation occurred in > 50% of all cohorts, and ≥ 65% of discontinuing patients changed to another anti-Parkinson drug.

Conclusions

This analysis described the heterogeneous use of MAO-BIs as an add-on to levodopa in Italy. Further clinical trials and real-world studies are encouraged to update the few existing guidelines and to align clinical practice strategies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40801-022-00308-4.

Effects of MAO-B inhibitors on non-motor symptoms and quality of life in Parkinson's disease: A systematic review

Non-motor symptoms (NMS) are common among patients with Parkinson's disease and reduce patients' quality of life (QOL). However, there remain considerable unmet needs for NMS management. Three monoamine oxidase B inhibitors (MAO-BIs), selegiline, rasagiline, and safinamide, have become commercially available in many countries. Although an increasing number of studies have reported potential beneficial effects of MAO-BIs on QOL and NMS, there has been no consensus. Thus, the primary objective of this study was to provide an up-to-date systematic review of the QOL and NMS outcomes from the available clinical studies of MAO-BIs. We conducted a literature search using the PubMed, Scopus, and Cochrane Library databases in November 2021. We identified 60 publications relevant to this topic. Overall, rasagiline and safinamide had more published evidence on QOL and NMS changes compared with selegiline. This was likely impacted by selegiline being introduced many years prior to the field embarking on the study of NMS. The impact of MAO-BIs on QOL was inconsistent across studies, and this was unlikely to be clinically meaningful. MAO-BIs may potentially improve depression, sleep disturbances, and pain. In contrast, cognitive and olfactory dysfunctions are likely unresponsive to MAO-BIs. Given the paucity of evidence and controlled, long-term studies, the effects of MAO-BIs on fatigue, autonomic dysfunctions, apathy, and ICD remain unclear. The effects of MAO-BIs on static and fluctuating NMS have never been investigated systematically. More high-quality studies will be needed and should enable clinicians to provide personalized medicine based on a non-motor symptom profile.

Low Dose Betahistine in Combination With Selegiline Increases Cochlear Blood Flow in Guinea Pigs

OBJECTIVE

Betahistine is frequently used in the pharmacotherapy for Menière's Disease (MD). Little is known about its mode of action and prescribed dosages vary. While betahistine had an increasing effect on cochlear microcirculation in earlier studies, low dose betahistine of 0.01 mg/kg bw or less was not able to effect this. Selegiline inhibits monoaminooxidase B and therefore potentially the breakdown of betahistine. The goal of this study was to examine whether the addition of selegiline to low dose betahistine leads to increased cochlear blood flow.

METHODS

Twelve Dunkin-Hartley guinea pigs were anesthetized, the cochlea was exposed and a window opened to the stria vascularis. Blood plasma was visualized by injecting fluoresceinisothiocyanate-dextrane and vessel diameter and erythrocyte velocity were evaluated over 20 minutes. One group received low dose betahistine (0.01 mg/kg bw) and selegiline (1 mg/kg bw) i.v. while the other group received only selegiline (1 mg/kg bw) and saline (0.9% NaCl) as placebo i.v.

RESULTS

Cochlear microcirculation increased significantly (P < .001) in guinea pigs treated with low dose betahistine combined with selegiline by up to 58.3 ± 38.7% above baseline over a period of up to 11 minutes. In one guinea pig, the increase was 104.6%. Treatment with Selegiline alone did not affect microcirculation significantly.

CONCLUSIONS

Low dose betahistine increased cochlear microcirculation significantly when combined with selegiline. This should be investigated in further studies regarding dose-effect relation in comparison to betahistine alone. Side effects, in particular regarding circulation, should be considered carefully in view of the clinical applicability of a combination therapy in patients with MD.

Monoamine Oxidase-B Inhibitors for the Treatment of Parkinson's Disease: Past, Present, and Future

Monoamine oxidase-B (MAO-B) inhibitors are commonly used for the symptomatic treatment of Parkinson’s disease (PD). MAO-B inhibitor monotherapy has been shown to be effective and safe for the treatment of early-stage PD, while MAO-B inhibitors as adjuvant drugs have been widely applied for the treatment of the advanced stages of the illness. MAO-B inhibitors can effectively improve patients’ motor and non-motor symptoms, reduce “OFF” time, and may potentially prevent/delay disease progression. In this review, we discuss the effects of MAO-B inhibitors on motor and non-motor symptoms in PD patients, their mechanism of action, and the future development of MAO-B inhibitor therapy.

A critical appraisal of MAO-B inhibitors in the treatment of Parkinson's disease

Since the 1980s, the MAO-B inhibitors have gained considerable status in the therapy of the Parkinson's disease. In addition to the symptomatic effect in mono- and combination therapies, a neuroprotective effect has repeatedly been a matter of some discussion, which has unfortunately led to a good many misunderstandings. Due to potential interactions, selegiline has declined in significance in the field. For the MAO-B inhibitor safinamide, recently introduced to the market, an additional inhibition of pathological release of glutamate has been postulated. At present, rasagiline and selegiline are being administered in early therapy as well as in combination with levodopa. Safinamide has been approved only for combination therapy with levodopa when motor fluctuations have occurred. MAO-B inhibitors are a significant therapeutic option for Parkinson's disease, an option which is too often not appreciated properly.

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.

Overnight switch from rasagiline to safinamide in Parkinson's disease patients with motor fluctuations: a tolerability and safety study

BACKGROUND AND PURPOSE

When switching between monoamine oxidase type B (MAO-B) inhibitors, a 15-day suspension period is a precautionary measure to avoid a serotonin syndrome and hypertensive crisis. However, this indication results in a major inconvenience for parkinsonian patients because of the worsening of their clinical condition. In routine clinical practice, neurologists often perform a substitution of these two drugs without solution of continuity (i.e. overnight), to avoid worsening of fluctuations and prolonged OFF periods. Therefore, a safety open label study was performed to investigate the possible risks of switching overnight from rasagiline to safinamide.

METHODS

The study population included 20 advanced patients with Parkinson's disease on stable treatment with rasagiline and levodopa (alone or in combination with other anti-parkinsonian medication). The possible occurrence of serotonin syndrome and hypertension was monitored through a strict clinical observation and a 24-h Holter recording (ABPM) performed twice, whilst subjects were on rasagiline and immediately after switching to safinamide.

RESULTS

No cases of serotonin syndrome or hypertensive crisis occurred during the study. Changes that were not significant occurred in the primary end-point: 24-h mean blood pressure (BP) had a mild +4.4% increase in the ABPM2 versus ABPM1 (P = 0.17), 24-h systolic and diastolic BP values were slightly higher at ABPM2 compared to ABPM1 (respectively +3.3%, P = 0.13; and 5.4%, P = 0.08) and 24-h systolic BP variability was unchanged between the two ABPM evaluations (from 8.6 ± 2.9 to 8.9 ± 1.8; P = 0.27).

CONCLUSION

The results of the present study confirm that the overnight switch from rasagiline to safinamide is safe and well tolerated by patients.

Safinamide in the treatment of Parkinson's disease

The deficiency pattern of neurotransmitters is heterogeneous in patients with Parkinson's disease. Consequence is an individual variable expression of motor and nonmotor features. They respond to agents with a broader spectrum of mode of actions, whereas dopamine substitution only targets impaired motor behavior. The pharmacological profile of safinamide includes reversible monoamine oxidase B inhibition and modulation of voltage-dependent sodium- and calcium channels with consecutive decline of glutamate release. Safinamide improves motor and nonmotor symptoms. Combination of safinamide with the catechol-O-methyltransferase inhibitor opicapone in one capsule is a promising future treatment alternative, which simplifies drug therapy in Parkinson's disease. Both agents complement each other in terms of application mode and efficacy on motor complications as adjuncts to levodopa therapy.

Rasagiline and selegiline modulate mitochondrial homeostasis, intervene apoptosis system and mitigate α-synuclein cytotoxicity in disease-modifying therapy for Parkinson's disease

Parkinson's disease has been considered as a motor neuron disease with dopamine (DA) deficit caused by neuronal loss in the substantia nigra, but now proposed as a multi-system disorder associated with α-synuclein accumulation in neuronal and non-neuronal systems. Neuroprotection in Parkinson's disease has intended to halt or reverse cell death of nigro-striatal DA neurons and prevent the disease progression, but clinical studies have not presented enough beneficial results, except the trial of rasagiline by delayed start design at low dose of 1 mg/day only. Now strategy of disease-modifying therapy should be reconsidered taking consideration of accumulation and toxicity of α-synuclein preceding the manifest of motor symptoms. Hitherto neuroprotective therapy has been aimed to mitigate non-specific risk factors; oxidative stress, mitochondrial dysfunction, apoptosis, deficits of neurotrophic factors (NTFs), inflammation and accumulation of pathogenic protein. Future disease-modify therapy should target more specified pathogenic factors, including deregulated mitochondrial homeostasis, deficit of NTFs and α-synuclein toxicity. Selegiline and rasagiline, inhibitors of type B monoamine oxidase, have been proved to exhibit potent neuroprotective function: regulation of mitochondrial apoptosis system, maintenance of mitochondrial function, increased expression of genes coding antioxidant enzymes, anti-apoptotic Bcl-2 and pro-survival NTFs, and suppression of oligomerization and aggregation of α-synuclein and the toxicity in cellular and animal experiments. However, the present available pharmacological therapy starts too late to reverse disease progression, and future disease-modifying therapy should include also non-pharmacological complementary therapy during the prodromal stage.

Different Generations of Type-B Monoamine Oxidase Inhibitors in Parkinson's Disease: From Bench to Bedside

Three inhibitors of type-B monoamine oxidase (MAOB), selegiline, rasagiline, and safinamide, are used for the treatment of Parkinson's disease (PD). All three drugs improve motor signs of PD, and are effective in reducing motor fluctuations in patients undergoing long-term L-DOPA treatment. The effect of MAOB inhibitors on non-motor symptoms is not uniform and may not be class-related. Selegiline and rasagiline are irreversible inhibitors forming a covalent bond within the active site of MAOB. In contrast, safinamide is a reversible MAOB inhibitor, and also inhibits voltage- sensitive sodium channels and glutamate release. Safinamide is the prototype of a new generation of multi-active MAOB inhibitors, which includes the antiepileptic drug, zonisamide. Inhibition of MAOB-mediated dopamine metabolism largely accounts for the antiparkinsonian effect of the three drugs. Dopamine metabolism by MAOB generates reactive oxygen species, which contribute to nigro-striatal degeneration. Among all antiparkinsonian agents, MAOB inhibitors are those with the greatest neuroprotective potential because of inhibition of dopamine metabolism, induction of neurotrophic factors, and, in the case of safinamide, inhibition of glutamate release. The recent development of new experimental animal models that more closely mimic the progressive neurodegeneration associated with PD will allow to test the hypothesis that MAOB inhibitors may slow the progression of PD.

Inhibitors of MAO-B and COMT: their effects on brain dopamine levels and uses in Parkinson's disease

MAO-B and COMT are both enzymes involved in dopamine breakdown and metabolism. Inhibitors of these enzymes are used in the treatment of Parkinson's disease. This review article describes the scientific background to the localization and function of the enzymes, the physiological changes resulting from their inhibition, and the basic and clinical pharmacology of the various inhibitors and their role in treatment of Parkinson's disease.

Safinamide: an add-on treatment for managing Parkinson's disease

Heterogeneous expression of neurotransmitter deficits results from onset and progression of Parkinson's disease. Intervals, characterized by reappearance of motor and associated certain nonmotor symptoms, determine the end of good tolerability and efficacy of oral levodopa therapy. These "OFF" states result from levodopa pharmacokinetics and disease progression-related deterioration of the central buffering capacity for fluctuations of dopamine levels. This review discusses safinamide as an add-on therapeutic agent in orally levodopa-treated patients with "OFF" phenomena. Safinamide provided beneficial effects on "OFF" symptoms in pivotal trials with doses of 50 or 100 mg once daily. Safinamide reversibly inhibits mono-amine oxidase B and declines abnormal glutamate release by modulation of potassium- and sodium ion channels. An ideal candidate for combination with safinamide is opicapone. This inhibitor of peripheral catechol-O-methyltransferase supports continuous brain delivery of levodopa and, thus, the continuous dopaminergic stimulation concept. Both compounds with their once-daily application and good tolerability may complement each other by reduction of necessary oral levodopa intakes and "OFF" times. Thus, a promising, future option will be combination of safinamide and opicapone in one formulation. It will reduce adherence issues and may complement levodopa treatment. It will probably cause less nausea and edema than a dopamine agonist/levodopa regimen.

Current and investigational non-dopaminergic agents for management of motor symptoms (including motor complications) in Parkinson's disease

INTRODUCTION

Parkinson's disease is characterized by a heterogeneous combination of motor and non motor symptoms. The nigrostriatal dopamine deficit is one of its essential pathophysiologic features. Areas covered: This invited narrative review provides an overlook over current available and future promising non dopaminergic therapeutics to modulate altered dopaminergic neurotransmission in Parkinson's disease. Current research strategies aim to proof clinical efficacy by amelioration of motor symptoms and preponderant levodopa related movement fluctuations. These so-called motor complications are characterized by involuntary movements as a result of an overstimulation of the nigrostriatal dopaminergic system or by temporary recurrence of motor symptoms, when beneficial effects of dopamine substituting drugs vane. Expert opinion: Non dopaminergic modulation of dopamine replacement is currently mostly investigated in well defined and selected patients with motor complications to get approval. However, the world of daily maintenance of patients with its individually adapted, so-called personalised, therapy will determine the real value of these therapeutics. Here the clinical experience of the treating neurologists and the courage to use unconventional drug combinations are essential preconditions for successful treatments of motor and associated non motor complications in cooperation with the patients and their care giving surroundings.

Simultaneous determination of MAO-A and -B activity following first time intake of an irreversible MAO-B inhibitor in patients with Parkinson's disease

We determined monoamine oxidase-A (plasma) and -B (platelets) enzyme activity in chronic levodopa treated patients with Parkinson's disease after first time intake of an irreversible monoamine oxidase-B inhibitor. One patient received 10 mg selegiline and eleven patients took 1 mg rasagiline. A significant decrease of monoamine oxidase-B activity appeared 2 and 4 h following monoamine oxidase-B inhibitor intake in comparison to baseline. We confirm with this design, that rasagiline and selegiline inhibit monoamine oxidase-B but not monoamine oxidase-A after single dosing.

Use of monoamine oxidase inhibitors in chronic neurodegeneration

INTRODUCTION

Neurotransmission by biogenic monoamines is important for brain function. Biogenic amine turnover employs the enzymes catechol-O-methyltransferase and monoamine oxidase in neuronal and glial cells. Inhibition of these enzymes elevates biogenic amine levels in the synaptic cleft. Subtype selectivity of inhibition is lost during long-term use of 'selective' monoamine oxidase inhibitors. Areas covered: This narrative review discusses use of monoamine oxidase inhibitors in the context with chronic neurodegeneration. Expert opinion: Antidepressant drugs increase synaptic concentrations of biogenic amines. In the aging brain, then one of the two enzymes involved in degrading synaptic amines, catechol-O-methyl transferase, increasingly catalyzes methylation processes. Therefore, metabolism by monoamine oxidase plays an incremental, predominant role in biogenic amine turnover, leading to greater oxidative stress. In patients with chronic neurodegenerative disorders, symptoms, such as depression and apathy, are often treated with drugs that elevate biogenic amine levels. This therapeutic strategy increases biogenic amine turnover, thereby generating neurotoxic aldehydes and enhanced oxidative stress, each of which influence and accelerate the course of neurodegeneration. We propose that antidepressant therapy should be initiated first with monoamine oxidase inhibitors only. If adequate clinical response is not achieved, only then they should be supplemented with a further antidepressant.

Current Pharmaceutical Treatments and Alternative Therapies of Parkinson's Disease

Over the decades, pharmaceutical treatments, particularly dopaminergic (DAergic) drugs have been considered as the main therapy against motor symptoms of Parkinson's disease (PD). It is proposed that DAergic drugs in combination with other medications, such as monoamine oxidase type B inhibitors, catechol-O-methyl transferase inhibitors, anticholinergics and other newly developed non-DAergic drugs can make a better control of motor symptoms or alleviate levodopa-induced motor complications. Moreover, non-motor symptoms of PD, such as cognitive, neuropsychiatric, sleep, autonomic and sensory disturbances caused by intrinsic PD pathology or drug-induced side effects, are gaining increasing attention and urgently need to be taken care of due to their impact on quality of life. Currently, neuroprotective therapies have been investigated extensively in pre-clinical studies, and some of them have been subjected to clinical trials. Furthermore, non-pharmaceutical treatments, including deep brain stimulation (DBS), gene therapy, cell replacement therapy and some complementary managements, such as Tai chi, Yoga, traditional herbs and molecular targeted therapies have also been considered as effective alternative therapies to classical pharmaceutics. This review will provide us updated information regarding the current drugs and non-drugs therapies for PD.

Nondopaminergic therapy of motor and nonmotor symptoms in Parkinson's disease: a clinician's perspective

Patients with Parkinson's disease suffer from impaired motor behavior due to the dopaminergic striatal deficit and nonmotor symptoms, which also result from nondopaminergic neuronal death. This review provides a personal opinion on treatment strategies for symptoms, resulting at least partially from nondopaminergic neurodegeneration, and on therapeutic modulation of dopaminergic neurotransmission. Patient-tailored treatment regimes on the basis of an individual risk benefit ratio as essential precondition try to balance all these symptoms. Individually varying heterogeneity of symptoms, nonlinear disease progression, treatment response, acceptance, tolerability and safety of applied therapies demand a close, consistent relationship between patient and treating physician. Daily maintenance of patients does not ask for too detailed treatment guidelines.

Impact of Pharmacotherapy on Quality of Life in Patients with Parkinson's Disease

Quality of life (QoL) is a patient-reported outcome frequently included in Parkinson's disease (PD) clinical trials as a secondary or tertiary endpoint. However, QoL is an important variable that reflects the impact of disease and treatment from the patients' perspective. In a chronic, neurodegenerative disease such as PD, with a wide range of complex symptoms, QoL provides valuable and comprehensive information on the patients' health status. This narrative review aims to evaluate the effect of specific PD treatments currently in use on patients' QoL measured with the Parkinson's Disease Questionnaire, 39-item (PDQ-39) or 8-item (PDQ-8) version. A quantification of this effect is provided by calculation of the relative change and effect size. These two parameters allow an intuitive standardized approach to the importance of change based on its magnitude. Some high-quality studies (Level I) were found for levodopa (immediate- or extended-release formulations), levodopa with added-on catechol-O-methyltransferase (COMT) inhibitors, levodopa/carbidopa gel for intestinal infusion, some dopamine agonists (ropinirole, cabergoline, pergolide), and the monoamine oxidase B (MAO-B) inhibitor safinamide. As a whole, these studies found a beneficial effect of variable magnitude, weak to moderate, on patients' QoL. Studies with a lower level of evidence or not providing enough data to estimate relative change and effect size, including those for the apomorphine subcutaneous pump, also reported improvement of QoL, but the evidence was insufficient to confirm the effect. More high-quality studies focused on QoL are needed to determine the real impact of PD drug treatments for this important outcome.

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.

Current status of safinamide for the drug portfolio of Parkinson's disease therapy

Parkinson's disease (PD) is characterized by a slowly ongoing neuronal death. This alters dopaminergic and glutamatergic neurotransmission and causes a wide variety of motor and non-motor features. Safinamide has a unique pharmacological profile, which combines modulation of dopamine metabolism by reversible, highly specific monoamine oxidase-B inhibition, blockage of voltage-dependent sodium channels, modulation of calcium channels and of glutamate release induced by abnormal neuronal activity. Therefore, safinamide represents an ideal candidate for the treatment of PD. This compound asks for one time daily intake only within an optimum dose range between 50 and 100 mg. In clinical trials, safinamide was well tolerated and safe, improved motor behavior even in combination with dopamine agonist only, ameliorated levodopa-associated motor complications. Safinamide has the potential to become an important compound for the therapy of PD, since its symptomatic efficacy appears to be superior to available monoamine oxidase-B inhibitors or N-methyl-d-aspartate receptor antagonists like amantadine, according to available trial outcomes.