Selegiline and cognitive function in Parkinson's disease

Monoamine-oxidase Type B Inhibitors and Cognitive Functions in Parkinson's Disease: Beyond the Primary Mechanism of Action

Symptoms of cognitive impairment are rather common since the early stage of Parkinson's disease (PD); they aggravate with disease progression and may lead to dementia in a significant proportion of cases. Worsening of cognitive symptoms in PD patients depends on the progression of subcortical dopaminergic damage as well as the involvement of other brain neurotransmitter systems in cortical and subcortical regions. Beyond the negative impact on disability and quality of life, the presence and severity of cognitive symptoms may limit adjustments of dopamine replacement therapy along the disease course. This review focuses on the consequences of the administration of monoamine-oxidase type Binhibitors (MAOB-I) on cognition in PD patients. Two drugs (selegiline and rasagiline) are available for the treatment of motor symptoms of PD as monotherapy or in combination with L-DOPA or dopamine agonists in stable and fluctuating patients; a further drug (safinamide) is usable in fluctuating subjects solely. The results of available studies indicate differential effects according to disease stage and drug features. In early, non-fluctuating patients, selegiline and rasagiline ameliorated prefrontal executive functions, similarly to other dopaminergic drugs. Benefit on some executive functions was maintained in more advanced, fluctuating patients, despite the tendency of worsening prefrontal inhibitory control activity. Interestingly, high-dose safinamide improved inhibitory control in fluctuating patients. The benefit of high-dose safinamide on prefrontal inhibitory control mechanisms may stem from its dual mechanism of action, allowing reduction of excessive glutamatergic transmission, in turn secondary to increased cortical dopaminergic input.

Efficacy and safety of selegiline for the treatment of Parkinson's disease: A systematic review and meta-analysis

Background

Drug efficacy generally varies with different durations. There is no systematic review analyzing the effect of selegiline for Parkinson's disease (PD) on different treatment duration. This study aims to analyze how the efficacy and safety of selegiline changes for PD over time.

Methods

PubMed, the Cochrane Library, Embase, China National Knowledge Infrastructure and Wanfang Database were systematically retrieved for randomized controlled trials (RCTs) and observational studies of selegiline for PD. The search period was from inception to January 18th, 2022. The efficacy outcomes were measured by the mean change from baseline in the total and sub Unified Parkinson's Disease Rating Scale (UPDRS), Hamilton Depression Rating Scale (HAMD) and Webster Rating Scale (WRS) scores. The safety outcomes were measured by the proportion of participants having any adverse events overall and that in different system organ classes.

Results

Among the 3,786 studies obtained, 27 RCTs and 11 observational studies met the inclusion criteria. Twenty-three studies reported an outcome which was also reported in at least one other study, and were included in meta-analyses. Compared with placebo, selegiline was found with a stronger reduction of total UPDRS score with increasing treatment duration [mean difference and 95% CIs in 1 month: -3.56 (-6.67, -0.45); 3 months: -3.32 (-3.75, -2.89); 6 months: -7.46 (-12.60, -2.32); 12 months: -5.07 (-6.74, -3.41); 48 months: -8.78 (-13.75, -3.80); 60 months: -11.06 (-16.19, -5.94)]. A similar trend was also found from the point estimates in UPDRS I, II, III, HAMD and WRS score. The results of observational studies on efficacy were not entirely consistent. As for safety, compared with placebo, selegiline had higher risk of incurring any adverse events [rate: 54.7% vs. 62.1%; odd ratio and 95% CIs: 1.58 (1.02, 2.44)], with the excess adverse events mainly manifested as neuropsychiatric disorders [26.7% vs. 31.6%; 1.36 (1.06, 1.75)] and no significant change over time. The statistically difference in overall adverse event between selegiline and active controls was not found.

Conclusion

Selegiline was effective in improving total UPDRS score with increasing treatment duration, and had a higher risk of incurring adverse events, especially the adverse events in the neuropsychiatric system.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: PROSPERO CRD42021233145.

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.

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.

The effects of antidepressants in Parkinson's disease: a meta-analysis

This study explored the therapeutic effect of antidepressants in Parkinson's disease (PD) using a meta-analysis. Altogether, 24 placebo-controlled trials qualified for inclusion and revealed that tricyclic antidepressants (TCAs) had a greater antidepressant effect relative to selective serotonin reuptake inhibitors (SSRIs), Qb(1) = 8.87, p < .01, and the mono-amine-oxidase inhibitor, selegiline, Qb(1) = 7.90, p < .01. Whereas TCAs produced a significant side effect profile (odds ratio = 3.07), adverse events were negligible with SSRIs (odds ratio = 1.83) and selegeline (odds ratio = 1.63). Antidepressants can be beneficial for patients with PD. However, the choice of antidepressants needs to take depressive symptomatologies into account while monitoring side effects.

Antidepressant studies in Parkinson's disease: a review and meta-analysis

The objective of this study was to determine effect sizes for both antidepressant treatment and placebo for depression in Parkinson's disease (PD), and to compare the findings with those reported in elderly depressed patients without PD. Recent reviews have concluded that there is little empiric evidence to support the use of antidepressants in PD; however, available data has not been analyzed to determine the effect size for antidepressant treatment in PD depression. A literature review identified antidepressant studies in PD. Suitable studies were analyzed using meta-analytic techniques, and effect sizes were compared with those from antidepressant studies in elderly patients without PD. Large effect sizes were found for both active treatment and placebo in PD, but there was no difference between the two groups. In contrast, active treatment was superior to placebo in depressed elderly patients without PD. In PD, increasing age and a diagnosis of major depression were associated with better treatment response. Results also suggest that newer antidepressants are well tolerated in PD. Despite the high prevalence of depression and antidepressant use in PD, controlled treatment research has been almost nonexistent. Meta-analysis results suggest a large but nonspecific effect for depression treatment in PD. In addition, PD patients may benefit less from antidepressant treatment, particularly selective serotonin reuptake inhibitors, than do elderly patients without PD.

Systematic review of antidepressant therapies in Parkinson's disease☆

Depression is the most common psychiatric disturbance in Parkinson's disease. We conducted a Cochrane systematic review to assess the efficacy and safety of antidepressant therapies in idiopathic Parkinson's disease. Relevant trials were identified from electronic databases, reference lists and queries to antidepressant manufacturers. Three randomised controlled trials examined oral antidepressants in 106 patients with Parkinson's disease. No eligible trials of electroconvulsive or behavioural therapy were found. In the first arm of the crossover trial by Andersen et al. (n=22), nortriptyline treated patients showed a larger improvement than placebo in a unique depression rating scale after 16 weeks although significance levels were not provided. A parallel group trial by Wermuth et al. (n=37) did not show any significant difference between citalopram and placebo in Hamilton score after 52 weeks. Rabey et al. (n=47) performed an open-label trial comparing fluvoxamine with amitriptyline. Similar numbers in each group had a 50% reduction in Hamilton score after 16 months. Major side effects including visual hallucinations and confusion were reported with fluvoxamine and amitriptyline. Insufficient data on the effectiveness and safety of antidepressant therapies in Parkinson's disease are available on which to make recommendations for their use. Large scale randomised controlled trials are urgently required.

Therapies for depression in Parkinson's disease

BACKGROUND

Depression is one of the most common neuropsychiatric disturbances in Parkinson's disease. 40% of observed variation in quality of life is due to depression. However, there is little hard evidence of the efficacy and safety of antidepressant therapies in Parkinson's disease.

OBJECTIVES

To assess the efficacy and safety of antidepressant therapies in idiopathic Parkinson's disease. Safety refers to both the direct side-effects of the therapy and also the therapy's interactions with the symptoms of Parkinson's disease and with the antiparkinsonian medications.

SEARCH STRATEGY

Relevant clinical trials were identified by electronic searches the Cochrane Controlled Trials Register (the Cochrane Library Issue 3, 2001), MEDLINE(1996-2001), EMBASE (1974-2001), PsychLit (1800's-2001), CINAHL (1982-2001) databases. The reference list of all trial reports and reviews were examined. Queries were sent out to all manufacturers and distributors of antidepressants within the UK requesting information on any relevant clinical trials.

SELECTION CRITERIA

Randomised controlled trials (RCT) examining licensed oral antidepressants, electroconvulsive therapy (ECT) or behavioural therapy in the treatment of depression in idiopathic Parkinson's disease.

DATA COLLECTION AND ANALYSIS

Data was extracted and assessed independently by three of the authors. Disagreements were resolved by discussion.

MAIN RESULTS

Three randomised controlled trials were found examining oral antidepressant medications in Parkinson's disease in a total of 106 patients. No eligible trials of ECT or behavioural therapy were found. In the first arm of the crossover trial by Andersen 1980 (n=22) patients in the nortriptyline group showed a larger improvement than placebo group in median depression score in a self-made 31-item depression rating scale after 16 weeks of treatment but statistical significance was not calculated. A parallel group trial by Wermuth 1998 (n=37) did not show any statistically significant difference between the citalopram and placebo groups in the Hamilton Depression Scale after 52 weeks of treatment. The third study by Rabey 1996 (n=47) was a randomised open-label trial to compare fluvoxamine versus amitriptyline. Similar numbers of patients in amitriptyline and fluvoxamine groups (60% vs 55%) had a 50% reduction of Hamilton score after 16 months of treatment. However, further assessment of this trial was not possible because only summary results were available from an abstract and attempts to contact the authors failed. Visual hallucinations or confusion had been reported in patients with fluvoxamine and amitriptyline. Otherwise, no other major side effects were found in the other two trials.

REVIEWER'S CONCLUSIONS

Insufficient data on the effectiveness and safety of any antidepressants therapies in Parkinson's disease are available on which to make recommendations for their use. Further large scale randomised controlled trials are urgently required in this area.

The effects of oral selegiline hydrochloride on learning and training in the dog: a psychobiological interpretation

1. Twenty two healthy, non-problem dogs were assessed for their acquisition of three different learning tasks on consecutive days and on the extinction of the response in the third. In Task 1, dogs were trained to walk in a circle on command. In Task 2, dogs were trained to retreat and sit on a mat. In Task 3, dogs were assessed for the acquisition and extinction of an operant response (pawing a panel). 2. Dogs were orally administered a placebo or selegiline hydrochloride at a dose of 0.5 mg/kg for a period of three weeks prior to testing and during the test period. 3. Dog's treated with selegiline tended to perform better at tasks which were clearly lured with a motivationally significant cue, performing a first correct response sooner and requiring fewer reinforcements to reach the success criterion. They were also significantly more likely to walk over a novel object placed on the floor of the test arena. In the absence of a significant lure, the selegiline treated dogs took significantly longer to reach the required performance criterion for the operant task. These dogs also extinguished their response more rapidly than the control group 4. In the third task, selegiline treated dogs were significantly less likely to look away and throughout all tasks these dogs tended to be less distracted than the placebo group. 5. These findings and other reports associated with the effects of selegiline on learning may be explained by reference to the effects of selegiline on dopaminergic structures associated with positive incentive motivation.

Impaired perception of vocal emotions in Parkinson's disease: influence of speech time processing and executive functioning

Little is known about the underlying dimensions of impaired recognition of emotional prosody that is frequently observed in patients with Parkinson's disease (PD). Because patients with PD also suffer from working memory deficits and impaired time perception, the present study examined the contribution of (a) working memory (frontal executive functioning) and (b) processing of the acoustic parameter speech rate to the perception of emotional prosody in PD. Two acoustic parameters known to be important for emotional classifications (speech duration and pitch variability) were systematically varied in prosodic utterances. Twenty patients with PD and 16 healthy controls (matched for age, sex, and IQ) participated in the study. The findings imply that (1) working memory dysfunctions and perception of emotional prosody are not independent in PD, (2) PD and healthy control subjects perceived vocal emotions categorically along two acoustic manipulation continua, and (3) patients with PD show impairments in processing of speech rate information.

Cognitive improvement during Tolcapone treatment in Parkinson's disease

The aim of this study was to evaluate the effects of Tolcapone, a reversible, selective inhibitor of catechol-O-methyltransferase, on the cognitive function of eight patients with advanced Parkinson's disease. They underwent neuropsychological and motor assessment at baseline and were re-evaluated after 6 months. During this period, they received Tolcapone three times daily, while the L-dopa dosage was progressively reduced. Significant improvements were observed in the attentional task, auditory verbal short-term memory, visuo-spatial recall, constructional praxia and motor symptoms. These data suggest that treatment with Tolcapone, in combination with L-dopa therapy, may determine a significant improvement in cognitive resources of patients with advanced Parkinson's disease.

Depression in Parkinson's disease. Pharmacological characteristics and treatment

Parkinson's disease (PD) is a common neurological illness and various degrees of depression frequently complicate its course. Risk factors for developing depression with PD include right-sided hemiparkinsonism, akinesia, increased severity of disability, anxiety and psychosis. Onset of parkinsonism at a younger age, female gender and the use of levodopa are arguable risk factors. Depression may be difficult to diagnose in patients with PD because the signs of the 2 disorders overlap. In addition, patients with atypical PD more commonly have depression than patients with classical PD presentations. Antidepressant response to antiparkinsonian treatment has been limited. Enhancement of catecholamine levels in the CNS by selegiline (deprenyl), a monoamine oxidase (MAO) type B inhibitor, has shown potential antidepressant as well as neuroprotective effects. Other MAO inhibitors have shown antidepressant efficacy in animal models but have not been well tolerated by patients with PD. A catechol-O-methyltransferase (COMT) inhibitor combined with an MAO inhibitor might synergistically maximise the levels of catecholamines in the CNS. Antidepressant medications used in patients without PD include tricyclic antidepressants (TCAs) and selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitors (SSRIs), but only TCAs have been carefully studied for their antidepressant effects in PD. Electroconvulsive therapy has proven efficacy as antidepressant therapy in patients with PD, and transcranial magnetic stimulation has provided temporary relief of depression under experimental conditions. Adverse effects of polypharmacy in the attempted treatment of depression in patients with PD are common in the elderly. A 'serotonin syndrome' has occurred frequently enough to preclude the coadministration of selegiline with SSRIs or TCAs, and multiple interactions between antiparkinsonian and antidepressant medications further complicate treatment strategies in patients with PD. An algorithmic approach to the pharmacological treatment of depression is described in this article.

The management of treatment-resistant depression in the medically ill

There are a few well-designed studies to systematically assess treatment-resistant depression in the medically ill patient. Psychiatrists, however, do have extensive clinical experience in treating depression in the medical patient. This experience can be useful in helping to determine treatment resistance and in selecting consequent treatment choices. A decision tree is offered in Table 1 to clarify the questions the clinician must answer. The first step is to evaluate the role of the medical illness and to decide whether or not treating that effectively will also clear the depression. Physicians may find it helpful to use a decision tree in initiating treatment of patients with depression and physical illness. Once it has been clarified that the diagnosis of depression is a correct one and that an antidepressant medication is in order, consideration of safety, side effects, and other current prescriptions used by the patient must occur. Drug-drug interactions as well as changes in the clearance of medications are critical to the effectiveness of the choice and tolerability for the patient. An antidepressant agent needs to be given for an adequate time with optimization of dosing. Augmenting a medication to increase its therapeutic action could be tried if one agent alone is not effective. An alternative approach is that the second drug selected might affect different neurotransmitters, and the combination of mechanisms would result in resolution of symptoms. Adding psychotherapy, especially when social supports are lacking, can be particularly helpful. ECT is an important consideration for severe depression when suicidal concerns are imminent or the patient has not responded to pharmacotherapy trials. While we await further studies of treatment-resistant depression in large enough numbers of patients with particular illnesses, we can use these guidelines to direct our decisions to switch or augment our initial choices to provide the safest, most effective care possible.

Synergistic interactions between COMT-/MAO-inhibitors and L-Dopa in MPTP-treated mice

Four experiments were performed to investigate the anti-akinesia effects of combining a sub-threshold dose (5 mg/kg, s.c.) of L-Dopa with different doses and combinations of COMT and MAO inhibitors upon the hypokinesia observed in MPTP-treated mice. Ro 40-7592 (1 and 3 mg/kg, s.c.), a novel COMT inhibitor, 60 min before L-Dopa reinstated both locomotion and rearing during a 2-hr interval after L-Dopa in MPTP mice; control mice were unaffected. The combination of Ro 40-7592 (3 mg/kg, s.c.) and pargyline (5 mg/kg, s.c.), a MAO inhibitor, with L-Dopa produced increases in both the peak effect and duration of action indicating a distinct potentiation of the effects of Ro 40-7592 by pargyline. L-Deprenyl, a MAOB inhibitor, together with L-Dopa, restored locomotion and rearing behaviour at all three doses applied (1, 3 and 10 mg/kg, s.c.); in control mice, motor activity was stimulated at the higher doses (3 and 10 mg/kg, s.c.), independent of L-Dopa administration. Combining L-Deprenyl (3 mg/kg, s.c.) with Ro 40-7592 (3 mg/kg, s.c.) one hr before L-Dopa to MPTP mice potentiated the restorative effects of each compound by itself, although no increase in peak effect was obtained. In the control mice, L-Deprenyl plus Ro 40-7592 or L-Deprenyl, by itself, stimulated motor activity following injection of L-Dopa. Marked dopamine (DA) depletions in the striatum of MPTP-treated mice were evident. The present results demonstrate that the effects of the COMT/MAO inhibitors in combination, and in conjunction with L-Dopa (at a dose that was without effect by itself), were well in excess of a summation of their individual effects. It was concluded therefore that a synergism of the restorative, anti-akinesic action of these compounds in MPTP-treated mice could offer a broader therapeutic spectrum in the treatment of Parkinson's disorder.

Memory and learning strategies in patients with Parkinson's disease

Parkinson's disease patients (PD) do not differ from control subjects (CS) when they have to execute a problem solving task in which external cues for solving the problem are given. However, when PD have to solve a problem by means of an internally generated strategy, they show a serious decrease in performance. We hypothesised that this distinction may also apply to the way PD and CS organize recall. In order to test our hypothesis the California Verbal Learning Test (CVLT) was administered to 59 PD and 30 CS. The test consists of five learning trials using a 16-word target list, composed of four items from each of four semantic categories. The fact that the word list was built on this implicit organization was not divulged in advance. The sequence in which the words were read is fixed; each subsequent word belongs to a category being different from the category to which the preceding word belongs. The organization in recall according to the semantic categories is considered to be the result of an unprompted, internally generated strategy. Recall according to the sequence in which the words are read by the experimenter, is viewed as an externally offered strategy. The results prove to be in line with our hypothesis: unlike CS who appeared to rely mainly and increasingly on an internally generated semantic organization, PD showed evidence of gradually adhering more to the externally imposed serial sequence.

Neuropsychological correlates of L-deprenyl therapy in idiopathic parkinsonism

1. Monoaminergic neurotransmitter systems are known to play an important role in neuropsychological functions and they are impaired in dementia of DAT and PD. 2. L-deprenyl is a monoamine-enhancing drug which at low doses selectively inhibits MAO-B, an enzyme whose brain activity has been reported to increase in normal aging and neurodegenerative dementing disorders. 3. The authors studied the effects of L-deprenyl, 10 mg/day, on several cognitive domains in idiopathic parkinsonians without dementia. Ten out-patients, treated with levodopa plus DDI, were tested before receiving L-deprenyl and retested six months after they had been treated with the drug. A control group of ten parkinsonian out-patients treated with only levodopa plus DDI, matched for age, educational level, severity and duration of extrapyramidal disease, was tested by the same neuropsychological battery and retested after a comparable time interval. 4. Statistically significant changes were noted in the verbal and visuospatial learning performances of PD patients treated with the combination of L-deprenyl and levodopa.