The launch of opicapone for Parkinson's disease: negatives versus positives

Safety review of current pharmacotherapies for levodopa-treated patients with Parkinson's disease

INTRODUCTION

Levodopa remains the gold standard for treatment of Parkinson's disease (PD). Patients develop complications with disease progression, necessitating adjunctive therapy to control fluctuations in motor and non-motor symptoms and dyskinesia. Knowledge of medication safety and tolerability is critical to ascertain the benefit-risk ratio and select an adjunctive therapy that provides the highest chance for medication adherence. Posing a challenge are the sheer abundance of options, stemming from the development of several new drugs in recent years, as well as differences in commercial drug availability worldwide.

AREAS COVERED

This review evaluates the efficacy, safety, and tolerability of current US FDA-approved pharmacotherapies for levodopa-treated PD patients, including dopamine agonists, monoamine oxidase type-B inhibitors, catechol-O-methyltransferase inhibitors, the N-methyl-D-aspartate receptor antagonist amantadine, and the adenosine receptor antagonist istradefylline. Data were taken from pivotal phase III randomized controlled and post-surveillance studies, when available, that directly led to FDA-approval.

EXPERT OPINION

No strong evidence exists to support use of a specific adjunctive treatment for improving Off time. Only one medication has demonstrated improvement in dyskinesia in levodopa-treated PD patients; however, every patient cannot tolerate it and therefore adjunctive therapy should be tailored to an individual's symptoms and risk for specific adverse effects.

Developmental and behavioral toxicity assessment of opicapone in zebrafish embryos

The use of clinical psychoactive drugs often poses unpredictable threats to fetal development. Catechol-O-methyltransferase (COMT) is a key enzyme that regulates dopamine metabolism and a promising target for modulation of cognitive functions. Opicapone, a newly effective third-generation peripheral COMT inhibitor, is used for the treatment of Parkinson's disease (PD) and possibly to improve other dopamine-related disorders such as alcohol use disorder (AUD) and obsessive-compulsive disorder (OCD). The widespread use of opicapone will inevitably lead to biological exposure and damage to the human body, such as affecting fetal development. However, the effect of opicapone on embryonic development remains unknown. Here, zebrafish larvae were used as an animal model and demonstrated that a high concentration (30 μM) of opicapone exposure was teratogenic and lethal, while a low concentration also caused developmental delay such as a shortened body size, a smaller head, and reduced locomotor behaviors in zebrafish larvae. Meanwhile, opicapone treatment specifically increased the level of dopamine (DA) in zebrafish larvae. The depletion response of the total glutathione level (including oxidized and reduced forms of glutathione) and changed antioxidant enzymes activities in zebrafish larvae suggest oxidative damage caused by opicapone. In addition, enhanced glutathione metabolism and cytokine-cytokine receptor interaction were found in zebrafish larvae treated with opicapone, indicating that opicapone treatment caused an oxidation process and immune responses. Our results provide a new insight into the significant developmental toxicity of opicapone in zebrafish larvae.

Unveiling the biopathway for the design of novel COMT inhibitors

Catechol-O-methyltransferase (COMT) is an enzyme responsible for the O-methylation of biologically active catechol-based molecules. It has been associated with several neurological disorders, especially Parkinson's disease (PD), because of its involvement in catecholamine metabolism, and has been considered an important therapeutic target for central nervous system disorders. In this review, we summarize the biophysical, structural, and therapeutical relevance of COMT; the medicinal chemistry behind the development of COMT inhibitors and the application of computer-aided design to support the design of novel molecules; current methodologies for the biosynthesis, isolation, and purification of COMT; and revise existing bioanalytical approaches for the assessment of enzymatic activity in several biological matrices.

Opicapone as an add-on to levodopa for reducing end-of-dose motor fluctuations in Parkinson's disease: a systematic review and meta-analysis

Aim: To assess the clinical efficacy and safety profile of opicapone (25 and 50 mg once daily) versus placebo. Patients: Levodopa-treated adults with Parkinson's disease. Material & methods: A systematic review and meta-analysis were conducted. Results: Opicapone provided a greater reduction in the absolute OFF-time, increased the chances of ≥1-h reduction in the OFF-time and ≥1-h increase in the ON-time compared with placebo. Receiving opicapone more often facilitated levodopa dose reduction versus placebo. There were no differences in the occurrence of adverse events (severe and leading to drug discontinuation), but receiving opicapone increased the frequency of dyskinesia. Conclusion: Opicapone demonstrated superior clinical efficacy to placebo, with a comparable general safety profile.

Absorption, metabolism and excretion of opicapone in human healthy volunteers

Aims

The absorption, metabolism and excretion of opicapone (2,5‐dichloro‐3‐(5‐[3,4‐dihydroxy‐5‐nitrophenyl]‐1,2,4‐oxadiazol‐3‐yl)‐4,6‐dimethylpyridine 1‐oxide), a selective catechol‐O‐methyltransferase inhibitor, were investigated.

Methods

Plasma, urine and faeces were collected from healthy male subjects following a single oral dose of 100 mg [¹⁴C]‐opicapone. The mass balance of [¹⁴C]‐opicapone and metabolic profile were evaluated.

Results

The recovery of total administered radioactivity averaged >90% after 144 hours. Faeces were the major route of elimination, representing 70% of the administered dose; 5% and 20% were excreted in urine and expired air, respectively. The C_max of total radioactivity matched that of unchanged opicapone, whereas the total radioactivity remained quantifiable for a longer period, attributed to the contribution of opicapone metabolites, involving primarily 3‐O‐sulfate conjugation (58.6% of total circulating radioactivity) at the nitrocatechol ring. Other circulating metabolites, accounting for <10% of the radioactivity exposure, were formed by glucuronidation, methylation, N‐oxide reduction and gluthatione conjugation. Additionally, various other metabolites resulting from combinations with the opicapone N‐oxide reduced form at the 2,5‐dichloro‐4,6‐dimethylpyridine 1‐oxide moiety, including nitro reduction and N‐acetylation, reductive opening and cleavage of the 1,2,4‐oxadiazole ring and the subsequent hydrolysis products were identified, but only in faeces, suggesting the involvement of gut bacteria.

Conclusion

[¹⁴C]‐opicapone was fully excreted through multiple metabolic pathways. The main route of excretion was in faeces, where opicapone may be further metabolized via reductive metabolism involving the 1,2,4‐oxadiazole ring‐opening and subsequent hydrolysis.

COMT Inhibitors in the Management of Parkinson's Disease

Levodopa treatment remains the gold standard for Parkinson's disease, but shortcomings related to the pharmacological profile, notably, oral administration and the consequent occurrence of motor complications, have led to the development of several add-on levodopa treatments or to research to improve the method of delivery. Motor fluctuations, and to a lesser extent non-motor fluctuations, concern half of the patients with Parkinson's disease after 5 years of disease and patients identified them as one of their most bothersome symptoms. Catechol-O-methyl transferase inhibitors (COMT-Is) are one of the recommended first-line levodopa add-on therapies for the amelioration of end-of dose motor fluctuations in patient with advanced Parkinson's disease. Currently, two peripheral COMT-Is are considered as first-line choices - entacapone (ENT), which was approved by the US Food and Drug Administration in 1999 and the European Committee in 1998; and opicapone (OPC), which was approved by the European Committee in 2016. A second-line COMT-I that requires regular hepatic monitoring, tolcapone (TOL), was approved by the Food and Drug Administration in 1998 and the European Committee in 1997. Of note, OPC also received Food and Drug Administration approval in 2021, but it is still only marketed in a few countries, including Germany, UK, Spain, Portugal, Italy, Japan, and USA, while ENT and TOL have a wider market. Our narrative review summarizes the pharmacokinetic/pharmacodynamic properties, clinical efficacy in terms of motor fluctuations, motor/non-motor symptoms, quality of life, and safety data of these three COMT-Is, as evidenced by randomized clinical trials, as well as by real-life observational studies. Overall, a phase III non-inferiority trial showed a similar effect between ENT and OPC on off-time (-60.8 min/day and -40.3 min/day, vs placebo, respectively), with a possible additional off-time reduction of 39 min/day, obtained when there is a switch from ENT to OPC. Concomitantly, TOL can reduce off-time by an average of 98 min/day. A significant though discrete concomitant reduction on the Unified Parkinson's Disease Rating Scale motor section (2-3 points) is obtained with all three drugs vs placebo. Data on quality of life are fewer and more heterogeneous, with positive results obtained especially in open-label studies. Effects on non-motor symptoms were investigated as secondary outcome only in a few studies, frequently by means of non-specific scales and a benefit was observed in open-label studies. Dopaminergic adverse effects were the most frequent, dyskinesia being the most common for the three drugs eventually requiring levodopa dose reductions. No urine discoloration and a very low incidence of diarrhea were found with OPC compared with ENT and TOL. Regular hepatic monitoring is needed only for TOL. A combination of COMT-Is with new formulations of levodopa, including the subcutaneous, intrajejunal, or new extended-release formulation, merits further exploration to improve the management of both mild and severe motor fluctuations.

Metabolism and disposition of opicapone in the rat and metabolic enzymes phenotyping

Opicapone (2,5‐dichloro‐3‐(5‐(3,4‐dihydroxy‐5‐nitrophenyl)‐1,2,4‐oxadiazol‐3‐yl)‐4,6‐dimethylpyridine 1‐oxide) is a selective catechol‐O‐methyltransferase inhibitor that has been granted marketing authorization in Europe, Japan, and United States. The present work describes the metabolism and disposition of opicapone in the rat obtained in support to its development and regulatory filling. Plasma levels and elimination of total radioactivity were determined after oral and intravenous administration of [¹⁴C]‐opicapone. The maximum plasma concentrations of opicapone‐related radioactivity were reached at early time points followed by a gradual return to baseline with a biphasic elimination. Fecal excretion was the primary route of elimination of total radioactivity. Quantitative distribution of drug‐related radioactivity demonstrated that opicapone and related metabolites did not distribute to the central nervous system. Opicapone was extensively metabolized in rats resulting in more than 20 phase I and phase II metabolites. Although O‐glucuronidation, ‐sulfation, and ‐methylation of the nitrocatechol moiety were the principal metabolic pathways, small amount of the N‐acetyl derivative was detected, as a result of reduction of the nitro group and subsequent conjugation. Other metabolic transformations included N‐oxide reduction to the pyridine derivative and reductive cleavage of 1,2,4‐oxadiazole ring followed by further conjugative reactions. Reaction phenotyping studies suggested that SULT 1A1*1 and *2 and UGT1A7, UGT1A8, UGT1A9, and UGT1A10 may be involved in opicapone sulfation and glucuronidation, respectively. However, the reductive metabolic pathways mediated by gut microflora cannot be excluded. Opicapone, in the rat, was found to be rapidly absorbed, widely distributed to peripheric tissues, metabolized mainly via conjugative pathways at the nitro catechol ring, and primarily excreted via feces.

Opicapone for the treatment of Parkinson's disease: a review

Purpose: Levodopa formulations are the workhorses of the labor against motor symptoms management in Parkinson's disease (PD). Progression of PD on levodopa inevitably leads to motor fluctuations. It is important to understand the safety and efficacy of opicapone, the most recent addition to the clinician's armamentarium against these fluctuations.Materials and methods: We review the development of COMT inhibitors in the treatment of PD as well as the efficacy and safety data reported in the currently published literature of opicapone in PD. The "currently published literature" is defined as all published, PubMed indexed trials including the word "opicapone." Finally, we compare opicapone to the competitor pharmaceuticals on the market to treat symptom fluctuations in PD and share our opinion of opicapone's place in clinical practice.Results: From the reported results of phase 3 and 4 trials of opicapone in PD, it is a safe and efficacious option to combat motor fluctuations for our PD patients taking levodopa. A reduction of "off" time by up to 1 h per day can be expected, increasing "on" time with fewer dyskinesias. Opicapone is not generally hepatotoxic, and the most reported side-effects-dyskinesia, dry mouth, dizziness, diarrhea, and constipation-were seen in only 1.4% of the OPTIPARK (a large phase 4 clinical trial) study population.Conclusions: One should consider utilizing opicapone, perhaps in combination with other augmenting medications with different mechanisms of action, to help treat motor and non-motor fluctuations in PD.

Targeting COVID-19 in Parkinson's Patients: Drugs Repurposed

The last couple of months have witnessed the world in a state of virtual standstill. The SARS-CoV-2 virus has overtaken the globe to economic and social lockdown. Many patients with COVID-19 have compromised immunity, especially in an aged population suffering from Parkinson 's disease (PD). Alteration in dopaminergic neurons and deficiency of dopamine in PD patients are the most common symptoms affecting 1% population above the age of 60 years. The compromised immune system and inflammatory manifestation in PD patients make them an easy target. The most common drugs under trial for COVID-19 are remdesivir, favipiravir, chloroquine and hydroxychloroquine, azithromycin along with adjunct drugs like amantadine with some monoclonal antibodies. Presently, clinically US FDA approved drugs in PD include Levodopa, catechol-O-methyl transferase (COMT) inhibitors, (Entacapone and Tolcapone), dopamine agonists (Bromocriptine, Ropinirole, Pramipexole, and Rotigotine), monoamine oxidase B (MAO-B) inhibitors (Selegiline and Rasagiline), amantadine and antimuscarinic drugs. The drugs have established mechanisms of action on PD patients with known pharmacodynamics and pharmacokinetic properties along with dose and adverse effects. Conclusion and relevance of this review focus on the drugs that can be tried on PD patients with SAR CoV-2 infection, in particular, amantadine that has been approved by all the developed countries as a common drug possessing both antiviral properties by downregulation of CTSL, lysosomal pathway disturbance and change in pH necessary to uncoat the viral proteins and anti- Parkinson properties. To deal with the significant prognostic adverse effect of SARS-CoV-2 on PD, the present-day treatment options, clinical presentation and various mechanisms are the need of the hour.

Clinical Utility of Opicapone in the Management of Parkinson's Disease: A Short Review on Emerging Data and Place in Therapy

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder, and levodopa (L-dopa) remains the most efficacious drug treatment for PD and a gold-standard for symptom control. Nonetheless, a significant majority of PD patients develop motor fluctuations over their disease course, with a significant impact on quality-of-life, meaning control of such complications translates into a fundamental clinical need. Catechol-O-methyl transferase (COMT) inhibitors (COMT-i) are used as first-line adjuvant therapy to L-dopa for end-of-dose (EoD) motor fluctuations, since they increase L-dopa availability in the brain by inhibiting its peripheral metabolism. Opicapone (OPC), a once-daily, long-acting COMT-i, is the most recent and potent of its class, having been licensed in Europe in 2016 as an add-on to preparations of L-dopa/DOPA decarboxylase inhibitors in PD patients with EoD motor fluctuations. More recently, it has also received approval in the USA and Japan in 2020. Two high-quality positive efficacy studies (double-blind Phase III clinical trials) established OPC efficacy with significant reduction in OFF time (average 60 minutes vs placebo), without concomitant increase of distressing dyskinesias during ON time. These beneficial effects were sustained in open-label extension studies, without unexpected safety issues or adverse events, with dyskinesia having been the most frequent complaint. OPC also avoids liver toxicity and gastrointestinal issues compared with previous COMT-i. In this review, we aimed to cover OPC’s lifecycle (synthesis to commercialization), its clinical pharmacological data, safety, tolerability and pharmacovigilance evidence, and discuss its role in the management of motor fluctuations in PD as well as its emerging place in international recommendations.

Recent Developments in New Therapeutic Agents against Alzheimer and Parkinson Diseases: In-Silico Approaches

Neurodegenerative diseases (ND), including Alzheimer's (AD) and Parkinson's Disease (PD), are becoming increasingly more common and are recognized as a social problem in modern societies. These disorders are characterized by a progressive neurodegeneration and are considered one of the main causes of disability and mortality worldwide. Currently, there is no existing cure for AD nor PD and the clinically used drugs aim only at symptomatic relief, and are not capable of stopping neurodegeneration. Over the last years, several drug candidates reached clinical trials phases, but they were suspended, mainly because of the unsatisfactory pharmacological benefits. Recently, the number of compounds developed using in silico approaches has been increasing at a promising rate, mainly evaluating the affinity for several macromolecular targets and applying filters to exclude compounds with potentially unfavorable pharmacokinetics. Thus, in this review, an overview of the current therapeutics in use for these two ND, the main targets in drug development, and the primary studies published in the last five years that used in silico approaches to design novel drug candidates for AD and PD treatment will be presented. In addition, future perspectives for the treatment of these ND will also be briefly discussed.

Opicapone for Parkinson's disease: clinical evidence and future perspectives

Since 2016, opicapone (OPC), a potent third-generation, long-acting, once-daily, peripheral catechol-O-methyltransferase inhibitor, is approved as an add-on to levodopa in Parkinson's disease patients with motor fluctuations. OPC 50 mg has showed to be able in reducing OFF time by an average of about 60 min daily compared with placebo, to further reduce OFF-time of about 39 min, when switched from ENT to OPC and to be safe. These beneficial effects of OPC were maintained for 1 year. Recently, several post hoc analysis and few pilot observational open-label studies, have suggested its efficacy and wider applicability for different phenotypes of motor complications and for Parkinson's disease stages. Here we review OPC applicability and perspectives, in the light of the more recently published analysis.

Safety and efficacy of tolcapone in Parkinson's disease: systematic review

PURPOSE

Tolcapone is an efficacious catechol-O-methyltransferase inhibitor for Parkinson's disease (PD). However, safety issues hampered its use in clinical practice. We aimed to provide evidence of safety and efficacy of tolcapone by a systematic literature review to support clinicians' choices in the use of an enlarging PD therapeutic armamentarium.

METHODS

We searched PubMed for studies on PD patients treated with tolcapone, documenting the following outcomes: liver enzyme, adverse events (AEs), daily Off-time, levodopa daily dose, unified Parkinson's disease rating scale (UPDRS) part-III, quality of life (QoL), and non-motor symptoms. FAERS and EudraVigilance databases for suspected AEs were interrogated for potential additional cases of hepatotoxicity.

RESULTS

Thirty-two studies were included, for a total of 4780 patients treated with tolcapone. Pertaining safety, 0.9% of patients showed liver enzyme elevation > 2. Over 23 years, we found 7 cases of severe liver injury related to tolcapone, 3 of which were fatal. All fatal cases did not follow the guidelines for liver function monitoring. FAERS and EudraVigilance database search yielded 61 reports of suspected liver AEs possibly related to tolcapone. Pertaining efficacy, the median reduction of hours/day spent in Off was 2.1 (range 1-3.2), of levodopa was 108.9 mg (1-251.5), of "On" UPDRS-III was 3.6 points (1.1-6.5). Most studies reported a significant improvement of QoL and non-motor symptoms.

CONCLUSION

Literature data showed the absence of relevant safety concerns of tolcapone when strict adherence to hepatic function monitoring is respected. Given its high efficacy on motor fluctuations, tolcapone is probably an underutilized tool in the therapeutic PD armamentarium.

Opicapone: A third generation COMT inhibitor

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Opicapone is a 3rd generation catechol-O-methyl transferase (COMT) inhibitor approved in April 2020 by the FDA.

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Opicapone is used once daily as adjunctive to levodopa/carbidopa to reduce “off” periods in patients with Parkinson’s disease.

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In clinical trials BIPARK I and II, 50 mg of opicapone once daily was shown to be noninferior to entacapone and reduced the mean off time by about 50 min when compared to placebo.

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Most common treatment-emergent adverse events for opicapone were dyskinesia, falls, insomnia, and elevated blood creatine phosphokinase levels; it has not been associated with severe hepatic impairment.

Objective: To provide a drug review of the newly FDA approved catechol-O-methyl transferase (COMT) inhibitor, opicapone, for the use of end-of-motor motor fluctuation in adults with Parkinson’s disease. Data sources: A literature search of Pubmed was performed till May 2020 using the following key terms: opicapone, Ongentys, and BIA 9-1067. Review articles, clinical trials, and drug monographs were reviewed. Study selection and data extraction: Relevant English-language monographs and studies conducted in humans were considered. Data synthesis: Opicapone was FDA approved for the treatment of end-of-motor motor fluctuation in adults with Parkinson’s disease in April 2020 based on two published randomized clinical trials that were 14 to 15 weeks in duration called BIPARK I and BIPARK II. Based on the clinical trials, 50 mg of opicapone once daily was shown to be noninferior to entacapone and reduced the mean off time by about 50 min when compared to placebo. Most common treatment-emergent adverse events were dyskinesia, falls, insomnia, and elevated blood creatine phosphokinase levels. Relevance to patient care and clinical practice: Opicapone overcomes the limitations associated with other COMT inhibitors since it is dosed once daily, well tolerated, and has not been associated with the risk of hepatic failure. When switching from entacapone to opicapone a reduction in “off” time of −39.3 min was also seen. Conclusions: Opicapone is a once daily 3rd generation COMT inhibitor that has the potential to benefit patients with Parkinson’s disease who are experiencing end-of-motor fluctuations.

Opicapone enhances the reversal of MPTP-induced Parkinson-like syndrome by levodopa in cynomolgus monkeys

Opicapone is a third generation nitrocatechol catechol-O-methyltransferase inhibitor that has received regional market approval for use as adjunctive therapy to levodopa in Parkinson's disease patients with motor fluctuations. This study evaluated the effects of opicapone as adjunct to levodopa in reversing a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced Parkinson's-like syndrome in cynomolgus monkeys in during opicapone preclinical development program. A Parkinson's-like syndrome was induced in cynomolgus monkeys by daily administrations of MPTP. Evaluation of the animals included scoring with the Primate Parkinsonism Motor Rating Scale (PPMRS) and assessment of locomotor activity. MPTP produced a stable Parkinson's-like behavioural syndrome as evidenced by tremor, postural changes, rigidity, impaired movements and balance, (PPMRS scores of 10-15) and decreased locomotor activity (13% of pre-MPTP values). Opicapone treatment alone, for 14 days, did not change Parkinson's-like symptoms nor decreased subject's locomotor behaviour. Ascending combinations of levodopa/benserazide dose-dependently decreased PPMRS and improved locomotor behaviour reaching statistical significance for levodopa/benserazide doses of 18/4.5 mg/kg and those effects were enhanced in opicapone treated subjects. Opicapone treated subjects as compared vehicle-treated, had markedly reduced erythrocyte catechol-O-methyltransferase activity, significantly increased plasma levodopa levels (1.8-fold higher AUC) with no statistically significant changes in C_max and significantly reduced 3-OMD AUC and C_max values (7.8- and 6.8-fold respectively). Opicapone potentiated the improvements in Parkinson's-like symptoms produced by levodopa/benserazide combinations with concomitant increase in plasma levodopa exposure, reduction of plasma 3-O-methyldopa levels and erythrocyte catechol-O-methyltransferase activity, results that were later demonstrated in 2 large Phase 3 studies in Parkinson's disease patients.

The preclinical discovery and development of opicapone for the treatment of Parkinson's disease

INTRODUCTION

Opicapone (OPC) is a well-established catechol-O-methyltransferase (COMT) inhibitor that is approved for the treatment of Parkinson's disease (PD) associated with L-DOPA/L-amino acid decarboxylase inhibitor (DDI) therapy allowing for prolonged activity due to a more continuous supply of L-DOPA in the brain. Thus, OPC decreases fluctuation in L-DOPA plasma levels and favors more constant central dopaminergic receptor stimulation, thus improving PD symptomatology.

AREAS COVERED

This review evaluates the preclinical development, pharmacology, pharmacokinetics and safety profile of OPC. Data was extracted from published preclinical and clinical studies published on PUBMED and SCOPUS (Search period: 2000-2019). Clinical and post-marketing data are also evaluated.

EXPERT OPINION

OPC is a third generation COMT inhibitor with a novel structure. It has an efficacy and tolerability superior to its predecessors, tolcapone (TOL) and entacapone (ENT). It also provides a safe and simplified drug regimen that allows neurologists to individually adjust the existing daily administration of L-DOPA. OPC is indicated as an adjunctive therapy to L-DOPA/DDI in patients with PD and end-of-dose motor fluctuations who cannot be stabilized on those combinations.

Factors to Consider in the Selection of Dopamine Agonists for Older Persons with Parkinson's Disease

Dopamine agonists (DAs) are frequently used in the management of Parkinson's disease (PD), a complex multisystem disorder influenced substantially by age-related factors. Over 80% of PD patients present after age 60 years and may have clinical features exacerbated by age-related comorbidities or decline in physiological compensatory mechanisms. Pharmacotherapy for motor symptoms in older persons is more likely to involve exclusive use of levodopa combined with a peripheral decarboxylase inhibitor throughout the course of the illness. Non-ergot DAs, such as pramipexole, rotigotine and ropinirole, may be used as de novo monotherapy for the control of motor symptoms in older persons, although they are less efficacious than levodopa therapy. DAs may also be considered as adjunct therapy in older persons when motor symptoms are no longer adequately controlled by levodopa or when motor fluctuations and dyskinesia appear. DAs may be used cautiously in older persons with cognitive impairment and orthostatic hypotension but should be avoided when there is a history or risk of psychosis or impulse control disorders.