Donepezil for Down's syndrome

Basal Forebrain Cholinergic Neurons: Linking Down Syndrome and Alzheimer's Disease

Down syndrome (DS, trisomy 21) is characterized by intellectual impairment at birth and Alzheimer's disease (AD) pathology in middle age. As individuals with DS age, their cognitive functions decline as they develop AD pathology. The susceptibility to degeneration of a subset of neurons, known as basal forebrain cholinergic neurons (BFCNs), in DS and AD is a critical link between cognitive impairment and neurodegeneration in both disorders. BFCNs are the primary source of cholinergic innervation to the cerebral cortex and hippocampus, as well as the amygdala. They play a critical role in the processing of information related to cognitive function and are directly engaged in regulating circuits of attention and memory throughout the lifespan. Given the importance of BFCNs in attention and memory, it is not surprising that these neurons contribute to dysfunctional neuronal circuitry in DS and are vulnerable in adults with DS and AD, where their degeneration leads to memory loss and disturbance in language. BFCNs are thus a relevant cell target for therapeutics for both DS and AD but, despite some success, efforts in this area have waned. There are gaps in our knowledge of BFCN vulnerability that preclude our ability to effectively design interventions. Here, we review the role of BFCN function and degeneration in AD and DS and identify under-studied aspects of BFCN biology. The current gaps in BFCN relevant imaging studies, therapeutics, and human models limit our insight into the mechanistic vulnerability of BFCNs in individuals with DS and AD.

Impact of cholinesterase inhibitors or memantine on survival in adults with Down syndrome and dementia: clinical cohort study

BACKGROUND

There is little evidence to guide pharmacological treatment in adults with Down syndrome and Alzheimer's disease. Aims To investigate the effect of cholinesterase inhibitors or memantine on survival and function in adults with Down syndrome and Alzheimer's disease.

METHOD

This was a naturalistic longitudinal follow-up of a clinical cohort of 310 people with Down syndrome diagnosed with Alzheimer's disease collected from specialist community services in England.

RESULTS

Median survival time (5.59 years, 95% CI 4.67-6.67) for those on medication (n = 145, mainly cholinesterase inhibitors) was significantly greater than for those not prescribed medication (n = 165) (3.45 years, 95% CI 2.91-4.13, log-rank test P<0.001). Sequential assessments demonstrated an early effect in maintaining cognitive function.

CONCLUSIONS

Cholinesterase inhibitors appear to offer benefit for people with Down syndrome and Alzheimer's disease that is comparable with sporadic Alzheimer's disease; a trial to test the effect of earlier treatment (prodromal Alzheimer's disease) in Down syndrome may be indicated. Declaration of interest A.S. has undertaken consulting for Ono Pharmaceuticals, outside the submitted work. Z.W. has received a consultancy fee and grant from GE Healthcare, outside the submitted work.

Down's syndrome and dementia

Down's syndrome is the most common genetic disorder seen in clinical practice: about 94% occurs because of non-disjunction of chromosome 21 and 3–5% because of translocation. Individuals increasingly survive to middle and old age, probably because of advances in medical treatment and improved living conditions. People with Down's syndrome have an increased risk of developing Alzheimer's disease in middle age. Within ICD–10 and DSM–IV classifications there is no consensus on the diagnosis of dementia in people with learning disability. New treatments have been licensed for use in mild to moderate Alzheimer's disease (e.g. acetylcholinesterase inhibitors and memantine). The comorbid picture of Down's syndrome and Alzheimer's disease presents a unique challenge to the clinician in both diagnosis and management.

New therapies for treating Down syndrome require quality of life measurement

Down syndrome (DS) is the most common genetic cause of cognitive deficits. Using mouse models and therapies for Alzheimer disease, researchers are exploring therapies that may improve cognitive function in people with DS. These developments shift the health economic paradigm of understanding DS from determining the appropriate screening tool to the effect of therapy on quality of life in those with DS. To date, there are no validated quality of life instruments for DS. Research should begin to develop instruments that can evaluate changes in quality of life in therapeutic trials and beyond.

The efficacy, safety, and tolerability of donepezil for the treatment of young adults with Down syndrome

The objective of our study was to assess the efficacy and safety of donepezil in young adults with Down syndrome (DS) but no evidence of Alzheimer disease (AD). A 12-week, randomized, double-blind, placebo-controlled study with a 12-week, open-label extension was conducted. The intervention consisted of donepezil (5-10 mg/day) in young adults (aged 18-35 years) with DS, but no AD. The primary measure was the Severe Impairment Battery (SIB) test and secondary measures were the Vineland Adaptive Behavior Scales (VABS), the Rivermead Behavioral Memory Test for Children, and the Clinical Evaluation of Language Fundamentals, Third Edition. At baseline, 123 subjects were randomly assigned treatment with donepezil or placebo. During the double-blind phase, SIB scores improved significantly from baseline in both groups, with no significant between-group differences. During the open-label phase, SIB scores in the original donepezil group remained stable; the original placebo group showed an improvement similar to that seen in the double-blind phase. VABS scores improved for donepezil, but not placebo, during the double-blind phase (observed cases, P = 0.03; last observation carried forward, P = 0.07). Post hoc responder analyses were significant for donepezil using three of five response definitions (P < or = 0.045). Adverse event rates were comparable to AD studies. In this first large-scale, multicenter trial of a pharmacological agent for DS, donepezil appears safe. Efficacy interpretation was limited for the primary measure due to apparent learning/practice and ceiling effects. Outcomes in post hoc analyses suggested efficacy in some, but not all subjects, consistent with phenotypic variability of DS. Additional studies are required to confirm potential benefits of donepezil in this population.

Donepezil for dementia in people with Down syndrome

BACKGROUND

Alzheimer's dementia (AD) is the most common form of dementia in people with Down Syndrome [DS]. Acetylcholine is a chemical found in the brain that has an important role in memory, attention, reason and language. Donepezil a reversible inhibitor of acetylcholinesterase, which is thought to maintain levels of acetylcholine, and is reported to have some benefits for people with AD in the general population. It is important to note that people with DS tend to present with AD at a much younger age than the normal population as well as having subtle differences in physiology (e.g. metabolism and heart rate) and may therefore have different requirements from the general population.

OBJECTIVES

To determine the effectiveness and safety of donepezil for people with DS who develop AD.

SEARCH STRATEGY

CENTRAL, MEDLINE, EMBASE, CINAHL, PsycINFO, BIOSIS, SCI, SSCI and the NRR were searched up to October 2008. We contacted the manufacturers of donepezil as well as experts in the field, to ask about reports of unpublished or ongoing trials.

SELECTION CRITERIA

Randomised controlled trials of participants with DS and AD in which treatment with donepezil was administered compared with a placebo group.

DATA COLLECTION AND ANALYSIS

Data were extracted from the published reports of the one relevant study identified.

MAIN RESULTS

The one study included in this review is a small (n=30) randomised controlled trial lasting 24 weeks. It was followed-up by an open label study with a crossover design.No significant differences were found on any four validated outcomes including global functioning and three measures of cognitive abilities and behavioural problems. 6 out of 16 carers (37%) of participants on donepezil and 2 out of 15 (13%) on placebo reported improvement. No data were available for day to day skills, institutionalisation, reduction in carers' stress or economic outcomes. Half the intervention group and 20% of the placebo group reported adverse events; two participants left because of adverse events.

AUTHORS' CONCLUSIONS

To date there is only one small randomised controlled study on the effect of donepezil. This shows, at best, a modest, non statistically significant trend in favour of people with Down syndrome and Alzheimer's dementia who are able to tolerate donepezil (this drug is currently only dispensed in relatively large doses and is contraindicated for those with cardiac and respiratory problems).This study does not provide good evidence on which to base practice. Findings in an open-label follow up to this study suggest possible benefit in some individuals. Further, larger randomised controlled studies with longer-term follow up are required.

Clinical trials in children with Down syndrome: Issues from a cognitive research perspective

Clinical and translational research play a key role in the transition of basic research discoveries to effective therapies. In Down syndrome (DS), these research approaches are not well utilized or developed to test new therapies to improve cognitive and/or adaptive function in this population. This article reviews the history of clinical trial research in children with DS from a cognitive research perspective and discusses important issues relevant to the conduct of well designed clinical trials for this population. Specific issues addressed include: funding, study design, study medication, subject recruitment and retention, safety, and efficacy challenges. The Duke Down Syndrome Research Team's program of clinical research of cholinesterase inhibitors for individuals with DS serves as the model application for the identified research principles. It is hoped that this article will raise awareness of the unmet need for clinical research in the cognitive and adaptive function of individuals with DS, especially children with DS.

Donepezil: a clinical review of current and emerging indications

This article reviews the piperidine derivative, donepezil hydrochloride (E2020, Aricept), a reversible central acetylcholinesterase inhibitor currently approved for treatment of mild-to-moderate Alzheimer's disease. Donepezil is well absorbed orally, unaffected by food or by time of administration; it reaches therapeutic levels in doses of 5-10 mg/day and peak plasma concentrations are obtained 3-4 h after oral administration. A single bedtime dose is recommended due to the long elimination half-life of the drug (70 h). Donepezil does not cause liver toxicity or significant drug interactions and is relatively well-tolerated. Initial side effects include nausea, vomiting, diarrhoea, insomnia, muscle cramps, fatigue, anorexia and syncope. Caution is advised in patients with bradycardia. Long-term use of donepezil in AD has been found to delay nursing-home placement and to result in caregiver respite. Donepezil also slows deterioration of cognition and global function in patients with moderate-to-severe AD, with improvement of abnormal behaviours. In addition to AD, donepezil demonstrates significant improvement in cognition, global function and activities of daily living in comparison with placebo-treated patients with vascular dementia and has potential therapeutic benefit for other neurological conditions.

Dramatic Improvement in down Syndrome—Associated Cognitive Impairment with Donepezil

OBJECTIVE:

To report 2 cases of patients with Down syndrome and severe cognitive impairment who gained dramatic improvements in quality of life (QOL) upon donepezil treatment.

CASE SUMMARIES:

Case 1. A 38-year-old woman with Down syndrome, diagnosed with secondary progressive dementia when her mental state had deteriorated rapidly after graduation from junior high school, started donepezil treatment. The loading dose was 3 mg/day and was increased to 5 mg/day for maintenance. One month after the dose was increased, adverse effects such as soft stool and urinary incontinence appeared. These adverse effects disappeared when the dose was decreased again to 3 mg/day. Her QOL improved dramatically with this minimal dose. She recovered verbal and written communication skills that she had lost for the past 21 years. Case 2. A 22-year-old man with Down syndrome, who had been diagnosed as having severe mental retardation, was put on donepezil therapy. Both loading and maintenance doses were 3 mg/day. His QOL had also dramatically improved, with some recovery in verbal communication. Transient agitation/violence and transient muscle weakness appeared during the first few months of treatment.

DISCUSSION:

Patients with Down syndrome may be more sensitive to donepezil therapy than others and may benefit from this medicine, although they may also have adverse effects more frequently.

CONCLUSIONS:

Donepezil may be a useful medicine for some patients with Down syndrome with severe cognitive impairment or mental retardation if the adverse effects are manageable.

Progressive Worsening of Adaptive Functions in Down Syndrome May Be Mediated By the Complexing of Soluble Aβ Peptides With the α7 Nicotinic Acetylcholine Receptor: Therapeutic Implications

In persons with Down syndrome, soluble Abeta peptides, which result from the processing of the amyloid precursor protein, appear in the brain decades before the extracellular deposition of neuritic plaques. These soluble amyloidogenic peptides accumulate intraneuronally and can be secreted extracellularly. Their appearance has been reported in the brains of fetuses with Down syndrome. The extra gene dosage effect associated with trisomy 21 results in abnormalities of the processing of amyloid precursor protein in persons with Down syndrome. Abeta peptides, especially Abeta1-42, have been shown to form tight complexes with the alpha7 nicotinic acetylcholine receptor, interfering with transduction of the acetylcholine signal by this nicotinic receptor subtype. Furthermore, the selective binding of Abeta peptides by this nicotinic acetylcholine receptor subtype is associated with cytotoxicity. The alpha7 nicotinic acetylcholine receptor has unique electrophysiologic properties and plays a prominent role in normal psychophysiologic processes (eg, sensory inhibition) and cognition. In persons with Down syndrome there is a decrease in the ability to perform instrumental activities of daily living that worsen with aging. The progressive worsening of adaptive functions and cognition in persons with Down syndrome may be, at least in part, mediated by interference with this receptor by soluble Abeta peptides. In view of this complex formed by soluble Abeta peptides and the alpha7 nicotinic acetylcholine receptor, cholinergic interventions that have been developed for Alzheimer disease, including selective nicotinic ones, should be explored in Down syndrome. Ideally, selective cholinergic interventions would slow the progression of the worsening of adaptive function and emergence of dementia in persons with Down syndrome.

Donepezil for the treatment of language deficits in adults with Down syndrome: a preliminary 24-week open trial

At present, there is no proven pharmacologic treatment for cognitive or language impairments in Down syndrome (DS). Cholinergic deficits have been documented in DS and linked to cognitive deficits. This study is a 24-week open-label clinical trial of donepezil hydrochloride for the treatment of language deficits in adults with DS. To our knowledge, this is the first prospective study to evaluate systematically the effects of donepezil, a cholinesterase inhibitor, on specific language domains in DS. The main finding that emerged was an improvement in expressive language performance following donepezil therapy. Despite the multiple methodological limitations, the results raise important questions regarding the role of the cholinergic system in language function and the specific effect of cholinergic therapy in the treatment of language impairment in DS. The results support the need for large-scale controlled studies of the effects of donepezil treatment on language and on other cognitive domains in DS.

Progress in clinical neurosciences: Treatment of Alzheimer's disease and other dementias--review and comparison of the cholinesterase inhibitors

BACKGROUND

Alzheimer's disease (AD) is the most common cause of dementia in older adults. Acceptance of the cholinergic hypothesis led to a search for medications which could enhance central cholinergic activity in this condition. There are now three cholinesterase inhibitors available for the treatment of AD in Canada.

OBJECTIVES

To review the currently available cholinesterase inhibitors approved for the treatment of AD in Canada and to provide guidance on who and how to treat with these agents.

RESULTS

Donepezil, rivastigmine, and galantamine are approved for the treatment of AD in Canada. In clinical trails, patients with mild to moderate AD treated with these agents experienced modest improvements in cognition, function, behaviour, and/or global clinical state. The magnitude of benefits seen with each agent appeared to be similar. While to date, there is no convincing evidence that one is more efficacious or effective, they do differ in their pharmacokinetics, additional mechanisms of action, and side effect profiles. Therefore, the selection of agent will be based on considerations such as side effect profiles, ease of administration, personal familiarity/experience, and beliefs about the importance of the noted differences in their pharmacokinetics and additional mechanisms of action.

CONCLUSION

We believe that these agents should be offered to all individuals with a mild to moderate dementia where Alzheimer's pathology is felt to be a contributing factor. We view all three available cholinesterase inhibitors as first-line drugs.

Present and future pharmacotherapeutic options for adult attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is often a lifelong condition. When untreated or undertreated, it appears to have a deleterious impact upon the daily functioning of the majority of adults that were diagnosed with this condition during childhood. Effective treatment, under the best circumstances, is multi-modal. The recent MTA study staged by the United States government confirmed the primary role of psychostimulants for children with this condition. The findings from this study have been generalised to adults that also have ADHD, particularly in cases where there is a well-defined longitudinal history dating back to early childhood. Psychostimulants remain a viable first-choice strategy for adults with ADHD. There are idiosyncratic differences in response to the various psychostimulants for any given individual with ADHD. Furthermore, the emergence of long-acting, once daily psychostimulant medications is likely to improve the calibre of care for adults with ADHD. A number of alternative pharmacotherapies have been studied, or are being developed, for adults with ADHD. These pharmacotherapies include antidepressant medications that affect dopaminergic and noradrenergic bioavailability, as well as cholinergic agents. In addition, agents that manipulate histaminergic and glutaminergic receptors are being studied as possible non-stimulant alternatives in the management of adult ADHD. More information is needed before any definitive statements can be made concerning the feasibility and utility of these non-stimulant medication approaches.

Donepezil for Alzheimer's disease: pharmacodynamic, pharmacokinetic, and clinical profiles

Donepezil was developed in order to overcome the disadvantages of physostigmine and tacrine. Its use is based on the cholinergic hypothesis. Donepezil is a piperidine-based, reversible acetylcholinesterase inhibitor, that is chemically unrelated to other cholinesterase inhibitors. It was developed for the symptomatic treatment of Alzheimer's disease (AD). Donepezil is highly selective for acetylcholinesterase with a significantly lower affinity for butyrylcholinesterase, which is present predominantly in the periphery. Phase I and II clinical trials demonstrated donepezil's favorable pharmacokinetic, pharmacodynamic and safety profile. There is no need to modify the dose of donepezil in the elderly or in patients with renal and hepatic failure. Pivotal phase-III trials in the US, European countries, and Japan showed that donepezil significantly improved cognition and global function in patients with mild to moderate AD. In long-term trials, donepezil maintained cognitive and global function for up to 1 year prior to the resumption of gradual deterioration. Donepezil is generally well tolerated; most of its adverse events are mild, transient and cholinergic in nature. Donepezil produces no clinically significant changes in laboratory parameters, including liver function. The drug is approved for the treatment of mild to moderate Alzheimer's disease, but donepezil therapy does not have to be discontinued if a patient continues to deteriorate. Possible new indications for donepezil in psychiatric and neurologic diseases, other than AD, include dementia with Lewy bodies, brain injury, attention deficit hyperactivity, multiple sclerosis, Down's syndrome, delirium, mood disorders, Huntington's disease and sleep disorders.