Pharmacology of acetylcholinesterase inhibitors and N-methyl-D-aspartate receptors for combination therapy in the treatment of Alzheimer's disease

The search for effective treatments of Alzheimer's disease (AD) is one of the major challenges facing modern medicine. Acetylcholinesterase (AChE) inhibitors (AChEIs) are effective for the treatment of mild to moderate AD, and memantine, an N-methyl-D-aspartate (NMDA) inhibitor, has been approved for moderate to severe AD. Galantamine is of particular interest because it has a dual mechanism of action: it is postulated to be both an AChEI and an allosteric modulator of nicotinic receptors. Modulation of NMDA and nicotinic receptors by memantine and galantamine may provide an optimal combination therapy for AD. The cholinergic and glutamatergic neurotransmitter systems, which share a close functional relationship, may play a role in the pathogenesis of AD. Close examination of the pharmacology of the 2 compounds suggests that galantamine can augment memantine's glutamatergic noise suppression while simultaneously enhancing the physiologic glutamatergic signal. The link between these systems suggests that AD therapies, which capitalize on this relationship, may be more effective in improving cognition than approaches focusing on a single system.

Mood disorders in the elderly

Mood disorders in the elderly are a growing source of morbidity and mortality. Unfortunately, mood disorders in later life frequently are not diagnosed and treated. Appropriate, prompt diagnosis and treatment of late-life mood disorders can significantly improve the quality of life of patients and families and may prove life saving. Current treatments can help most older adults with mood disorders. Future treatments are promising, particularly for those with treatment-resistant depression.

Rationale for Combination Therapy With Galantamine and Memantine in Alzheimer's Disease

A combination of cholinergic and glutamatergic dysfunction appears to underlie the symptomatology of Alzheimer's disease. Therefore, one hypothesis is that treatment strategies should address impairments in both systems. Galantamine is an acetylcholinesterase inhibitor that, unlike other acetylcholinesterase inhibitors, has a postulated dual mode of action as a nicotinic receptor modulator. Galantamine has demonstrated long-term efficacy in improving or maintaining cognition, functionality, and behavior in patients with mild to moderate Alzheimer's disease. Memantine, a noncompetitive N-methyl-D-aspartate-receptor antagonist, reduces deterioration in cognition and function in patients with moderate to severe Alzheimer's disease. Pharmacokinetic and pharmacodynamic as well as ongoing observation studies support the concept of adjunctive therapy with memantine in patients with advanced moderate Alzheimer's disease currently treated with an established galantamine regimen. The potential to modulate both acetylcholine and glutamate pathways in Alzheimer's disease presents a novel treatment strategy for the management of mild to moderately severe Alzheimer's disease.

Rivastigmine for Alzheimer's disease

Alzheimer's disease is the most common form of neurodegenerative dementia and poses considerable health challenges to both patients and their families. Rivastigmine is a powerful slow-reversible, noncompetitive carbamate cholinesterase inhibitor that is approved for the treatment of mild-to-moderate Alzheimer's disease. Randomized, double-blind, placebo-controlled trials of up to 6 months duration have shown beneficial effects of rivastigmine compared with placebo in measures of cognition and global functioning. Less rigorous but growing data suggest that the beneficial effects may endure for up to 5 years, extend to more advanced stages of Alzheimer's disease and may occur in noncognitive domains, such as activities of daily living and the behavioral symptoms of Alzheimer's disease. Evidence from controlled studies also supports the use of rivastigmine for cognitive and behavioral symptoms in Alzheimer's disease associated with vascular risk factors, dementia with Lewy bodies and Parkinson's disease dementia. Early and continued treatment of Alzheimer's disease with rivastigmine maximizes the observed beneficial effects. The most prominent adverse effect of rivastigmine is centrally mediated cholinergic gastrointestinal events, which can be minimized by slower dose-escalation intervals and administration with a full meal. Therapeutic dosing is 6-12 mg/day given twice daily, with higher doses having the potential for greater benefits.

Rationalizing therapeutic approaches in Alzheimer's disease

Deficits in cholinergic and glutamatergic neurotransmission have been linked to the symptomatology of Alzheimer's disease, and current therapies for Alzheimer's, including cholinesterase inhibitors (ChEIs) and the N-methyl-d-aspartate receptor antagonist memantine, have been developed to compensate for these deficits. This article reviews the results of clinical trials involving agents approved by the United States Food and Drug Administration for use in the treatment of Alzheimer's disease (namely, ChEIs for mild to moderate Alzheimer's and memantine for moderate to severe Alzheimer's). In particular, the efficacy of current monotherapy strategies in the treatment of cognitive and functional symptoms of Alzheimer's disease will be addressed. In addition, data from a clinical trial examining the use of a ChEI in combination with memantine will also be discussed, as it has been hypothesized that ChEIs and memantine may offer synergistic benefits due to their distinct mechanisms of action.

Alzheimer's disease pathways to practice: assessing diagnosis and outcome measures

Alzheimer's disease is the most common form of dementing illness, affecting nearly 4.5 million Americans according to current estimates. The disease exhibits a strong association with old age, and is not commonly observed in individuals <65 years of age. Among individuals >65 years of age, the prevalence of Alzheimer's disease is ∼10%, and nearly half of all persons >85 years of age are affected by this condition. Given the apparent link between Alzheimer's risk and increasing age, as well as expected changes in the demographic structure of the United States population, it has been projected that the number of Americans with Alzheimer's disease will reach unprecedented levels in the coming years. In fact, it has been predicted that, barring the development of novel preventive therapies, the number of US residents with Alzheimer's will increase to 11–16 million by the year 2050.

The expected rise in the number of Alzheimer's disease cases represents a daunting challenge, due to the far-reaching negative impact of the disease. Alzheimer's disease is a condition that not only has profound effects on the affected patient but also takes a dramatic toll on the patient's primary caregiver, who is in many cases the spouse or an adult child of the patient. Patients with Alzheimer's experience cognitive and functional declines, often in association with behavioral disturbances, while caregivers frequently suffer reductions in quality of life attributable to the immense emotional, physical, and financial burdens associated with the task of providing care.

Effect of rivastigmine in the treatment of behavioral disturbances associated with dementia: review of neuropsychiatric impairment in Alzheimer's disease

Cognitive decline is conventionally regarded as the defining clinical symptom of Alzheimer's disease (AD), but behavioral and neuropsychiatric symptoms are also present throughout the course of the disease. In fact, behavioral symptoms may appear before cognitive decline is diagnosed. The presence of these symptoms may predict an increasing need for community-based services or even nursing home placement. The characteristic behavioral and neuropsychiatric symptoms associated with AD may be related to the same pathophysiology that underlies the cognitive abnormalities. AD is characterized by a loss of cholinergic neurons as well as by the presence of neurofibrillary tangles (NFTs) and senile plaques in brain regions with cholinergic deficits, resulting in a deficiency in acetylcholine (ACh) in areas of the brain that modulate cognition, behavior, and emotion. Cholinesterase inhibitors are thought to augment or maximize the concentration of ACh in the synaptic cleft. Rivastigmine is a dual inhibitor of both acetylcholin esterase (AChE) and butyrylcholinesterase (BuChE), enzymes involved in hydrolysis of ACh. Literature searches using MEDLINE and EMBASE databases were performed to identify studies of rivastigmine (through August 2005) that assessed neuropsychiatric aspects of AD. Rivastigmine has been demonstrated to be safe and effective in stabilizing or improving the cognitive symptoms of AD in 3 large, well-controlled, randomized clinical trials, which also demonstrated that rivastig mine improves overall global functioning. Smaller studies and meta-analyses of pooled data from the 3 large trials have suggested that rivastigmine may improve the behavioral and neuropsychiatric symptoms associated with AD.

Unmet Visual Needs of Alzheimer’s Disease Patients in Long-term Care Facilities

INTRODUCTION

The purpose of this study was to determine the prevalence of uncorrected visual disorders in nursing home patients with Alzheimer's disease (AD) and to determine whether appropriate corrective measures were taken by nursing home staff. This study was conducted at 2 community nursing homes in the St Louis area. Whereas previous studies have shown that visual impairment is common among all residents of nursing facilities, our study was focused specifically on residents with AD. This population is less able to effectively express needs and more likely to endure unaddressed visual deficits. For AD patients, it is important to offer appropriate corrective remedies in order to maintain as much functional independence as possible.

METHODS

A retrospective cohort study was conducted in 2 private, skilled nursing facilities in St Louis County thought to be representative of community nursing homes in the United States. All subjects were patients with a diagnosis of dementia of probable AD. Demographic information collected included age, sex, and race. Mini-Mental State Examination scores were also obtained. The patients, their families, and nursing staff were interviewed to determine the patients' visual history, corrective measures, and the usage of corrective eyewear before and after admission to the nursing homes. The data were summarized to demonstrate how many patients suffered from uncorrected errors of refraction and what factors contributed to their visual status.

RESULTS

Of the total of 85 patients included in the study, 80 (94.1%) required glasses for correction of presbyopia, myopia, or both. However, 25 of the 80 residents had not actively been using glasses since entering the nursing home. Of these 25 residents not wearing proper eyewear, 9 residents were too cognitively impaired to request them, 8 residents had broken or misplaced them, and 8 residents had prescriptions that were no longer sufficient to correct their vision.

DISCUSSION

Our study found that nearly one third of the visually impaired nursing home residents with AD (25 of 80 patients) were not using their required eyewear. These 25 patients were the population of most interest because they were most likely to benefit from intervention. Many of these patients were not using glasses because they had been lost, damaged, or were no longer sufficient to correct their vision.

CONCLUSIONS

We have presented 3 recommendations intended to prevent uncorrected visual acuity in nursing home residents with dementia: (1) Label eyewear in appropriate patient populations to provide rapid identification in the event of misplacement, (2) recommend that an extra pair of glasses be made available if the current pair would be lost or damaged, and (3) ensure that all residents have annual or biannual eye exams. If adequate steps are taken to prevent unnecessary visual impairment in AD patients, it would limit their dependence on others, reduce the burden on nursing staff, and improve the patients' overall quality of life.

Diagnosis and treatment of Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common cause of dementia. It is one of the principal causes of disability and decreased quality of life among older adults. Progress in our clinical knowledge of AD has led to more reliable diagnostic criteria and accuracy, and research efforts are expanding to uncover the earliest manifestations and even the presymptomatic phases of the disease. The diagnosis of AD is primarily one of inclusion and usually can be made using standardized clinical criteria. There is currently no cure for AD. Current treatment focuses on establishing an early accurate clinical diagnosis, early institution of cholinesterase inhibitors and/or N-methyl-D-aspartate (NMDA) receptor-targeted therapy. Treating medical comorbidities and dementia-related complications, ensuring that appropriate services are provided, addressing the long-term well-being of caregivers, and treating behavioral and psychological symptoms with appropriate nonpharmacologic and pharmacologic interventions also are important. The initiating and propagating pathologic processes and the anatomic location of the earliest changes will become new targets of research and therapeutic development. A possible precursor of AD, mild cognitive impairment (MCI), is under investigation as a possible therapeutic starting point for disease-modifying interventions. This article provides a research update of current understanding in the diagnosis and treatment of AD and in emerging areas of interest such as MCI, detection of AD in the predementia phase, and neuroimaging in AD.

Activities of daily living in patients with dementia: clinical relevance, methods of assessment and effects of treatment

Disability, characterised by the loss of ability to perform activities of daily living (ADL), is a defining feature of dementia that results in growing caregiver burden and the eventual need for alternative care or nursing home placement. Functional decline in patients with dementia can also result from causes other than dementia, such as comorbid medical and psychiatric illnesses and sensory impairment. ADL consists of instrumental ADL (IADL) [complex higher order skills, such as managing finances] and basic ADL (BADL) [self-maintenance skills, such as bathing]. Assessment of IADL and BADL is recommended to establish a diagnosis of dementia. Functional assessment also helps the healthcare provider to offer appropriate counselling regarding safety concerns and need for custodial care. Functional capacity measures have been used increasingly in pharmacological trials of patients with Alzheimer's disease (AD) and related dementias, although at the present time these measures are generally not primary outcome measures. Functional impairment is not a uniform construct; rather, it is multifaceted and can be measured with various clinical instruments. Many scales have been validated for use in patients with AD for characterising functional impairment and evaluating the efficacy of treatment. Research to date indicates that cholinesterase inhibitors have the potential for modest but meaningful beneficial effects on ADL in patients with mild-to-moderate AD. Memantine also has promising beneficial effects on functional abilities in persons with moderate-to-severe AD. Assessment of ADL as a primary efficacy measure using a validated scale that is non-gender biased and cross-nationally relevant is recommended in new treatment trials of patients with AD and related dementias.

Electroconvulsive therapy in the elderly

ECT is a safe, useful, and effective treatment for a variety of disorders and can be administered safely in elderly patients. Efforts need to be undertaken to increase the awareness and acceptability of ECT treatments. As Carl Salzman says in the January 1998 issue of the American Journal of Psychiatry, "Let us not perpetuate outmoded, nonscientific and incorrect attitudes toward ECT in our younger colleagues. Rather, let us stimulate scientific curiosity and research into this cost-effective and safe psychiatric treatment."

Memantine treatment in patients with moderate to severe Alzheimer disease already receiving donepezil: a randomized controlled trial

CONTEXT

Memantine is a low- to moderate-affinity, uncompetitive N-methyl-D-aspartate receptor antagonist. Controlled trials have demonstrated the safety and efficacy of memantine monotherapy for patients with moderate to severe Alzheimer disease (AD) but no controlled trials of memantine in patients receiving a cholinesterase inhibitor have been performed.

OBJECTIVE

To compare the efficacy and safety of memantine vs placebo in patients with moderate to severe AD already receiving stable treatment with donepezil.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, double-blind, placebo-controlled clinical trial of 404 patients with moderate to severe AD and Mini-Mental State Examination scores of 5 to 14, who received stable doses of donepezil, conducted at 37 US sites between June 11, 2001, and June 3, 2002. A total of 322 patients (80%) completed the trial.

INTERVENTIONS

Participants were randomized to receive memantine (starting dose 5 mg/d, increased to 20 mg/d, n = 203) or placebo (n = 201) for 24 weeks.

MAIN OUTCOME MEASURES

Change from baseline on the Severe Impairment Battery (SIB), a measure of cognition, and on a modified 19-item AD Cooperative Study-Activities of Daily Living Inventory (ADCS-ADL19). Secondary outcomes included a Clinician's Interview-Based Impression of Change Plus Caregiver Input (CIBIC-Plus), the Neuropsychiatric Inventory, and the Behavioral Rating Scale for Geriatric Patients (BGP Care Dependency Subscale).

RESULTS

The change in total mean (SE) scores favored memantine vs placebo treatment for SIB (possible score range, 0-100), 0.9 (0.67) vs -2.5 (0.69), respectively (P<.001); ADCS-ADL19 (possible score range, 0-54), -2.0 (0.50) vs -3.4 (0.51), respectively (P =.03); and the CIBIC-Plus (possible score range, 1-7), 4.41 (0.074) vs 4.66 (0.075), respectively (P =.03). All other secondary measures showed significant benefits of memantine treatment. Treatment discontinuations because of adverse events for memantine vs placebo were 15 (7.4%) vs 25 (12.4%), respectively.

CONCLUSIONS

In patients with moderate to severe AD receiving stable doses of donepezil, memantine resulted in significantly better outcomes than placebo on measures of cognition, activities of daily living, global outcome, and behavior and was well tolerated. These results, together with previous studies, suggest that memantine represents a new approach for the treatment of patients with moderate to severe AD.

Diagnosis and treatment of Alzheimer's disease

The defining characteristic of Alzheimer's disease is cognitive impairment, but commonly this impairment is accompanied by mood and behavioral symptoms such as depression, anxiety, irritability, inappropriate behavior, sleep disturbance, psychosis, and agitation. The symptoms of Alzheimer's disease are not normative to the aging process. Diagnosis of Alzheimer's disease in the majority of cases can be made with confidence through office-based clinical assessment and informant interview. Alzheimer's disease is the most common of the dementing disorders and is exponentially increasing in incidence, projected to affect 8.64 million people in the United States by the year 2047. At present, no treatment can prevent or cure Alzheimer's disease, and the fact that Alzheimer's affects a geriatric population makes treatment all the more challenging. Therapies that could delay onset of symptoms even briefly would have a major impact on public health. As the prevalence of Alzheimer's disease increases, researchers are examining the efficacy of treatment options beyond the realm of the established cholinesterase inhibitors.

Herbals and botanicals in geriatric psychiatry

There is high prevalence of herbal medicine use among elderly people. Most patients do not reveal their herbal use to their physicians and pharmacists. The authors describe some commonly used herbal remedies in terms of their potential benefits and known adverse effects. The review also highlights the potentially serious risk of herb-drug interactions and discusses communication issues and regulatory concerns associated with use of herbal medicines. Health practitioners should remember to include herbal use history in their routine drug histories and remain informed of the beneficial and harmful effects of these treatments.

The ABC of Alzheimer's disease: behavioral symptoms and their treatment

Behavioral and psychological symptoms of dementia (BPSD) are a common manifestation of Alzheimer's disease (AD) and other dementia syndromes. Patients experience prominent and multiple symptoms, which are both distressing and a source of considerable social, health, and economic cost. Development of symptoms is in part related to progressive neurodegeneration and cholinergic deficiency in brain regions important in the regulation of behavioral and emotional responses including the cortex, hippocampus, and limbic system. Cholinesterase (ChE) inhibitors offer a mechanism-based approach to therapy to enhance endogenous cholinergic neurotransmission. Studies using ChE inhibitors have demonstrated their clear potential to improve or stabilize existing BPSD. Differences have been noted between selective acetylcholinesterase (AChE) inhibitors (donepezil and galantamine) and dual ChE inhibitors (rivastigmine) in terms of treatment response. While donepezil has shown efficacy in moderate to severe noninstitutionalized AD patients, conflicting results have been obtained in mild to moderate patients and in nursing home patients. Galantamine has been shown to delay the onset of BPSD during a five-month study but has been otherwise poorly studied to-date. Both donepezil and galantamine have not as yet demonstrated efficacy in reducing psychotic symptoms or in reducing levels of concomitant psychotropic medication use. Studies with the dual ChE inhibitor rivastigmine in mild to moderately severe AD and in Lewy body dementia (LBD) have shown improvements in behavioral symptoms including psychosis. Improvements have been maintained over a period of up to two years. In addition, institutionalized patients with severe AD have shown symptomatic benefits with a reduction in the requirement for additional psychotropic drugs following treatment with rivastigmine. The psychotropic properties associated with rivastigmine may in part be mediated through effects on butyrylcholinesterase. Current treatment options are limited for patients with dementia syndromes other than AD. However, data concerning rivastigmine in patients with LBD and preliminary studies in Parkinson's disease dementia and vascular dementia suggest a role for ChE inhibitors across the spectrum of dementia syndromes. Finally, studies that incorporated a delayed start design demonstrate that ChE inhibitors may delay the progression of BPSD.

Strategies for continued successful treatment of Alzheimer's disease: switching cholinesterase inhibitors

Cholinesterase (ChE) inhibitors represent the standard therapeutic approach to the treatment of Alzheimer's disease (AD). However, a proportion of patients experience lack or loss of therapeutic benefit with an initial agent, or discontinue due to safety/tolerability issues. In many instances, no alternative treatment is offered once the initial agent has been stopped. Thus, for many patients, the total duration of treatment is relatively short in comparison with the chronic nature of AD. Switching medications is a common therapeutic strategy within many drug classes across many clinical areas following a lack/loss of efficacy or safety/tolerability problems, and is also an increasingly important concept in the management of AD with ChE inhibitors. A number of open-label studies, where patients were switched from donepezil to rivastigmine, have indicated that approximately 50% of patients experiencing a lack/loss of efficacy with donepezil (a selective acetylcholinesterase [AChE] inhibitor) respond to subsequent treatment with rivastigmine (a dual AChE and butyrylcholinesterase inhibitor). In these studies, rivastigmine was well tolerated, and the occurrence of safety/tolerability problems with donepezil was not predictive of similar problems with rivastigmine. In the summer of 2002, leading neurologists and psychiatrists attended a medical experts meeting to discuss the clinical importance of switching ChE inhibitors in AD. The expert panel examined available clinical data, shared clinical experiences, and discussed current clinical guidelines for switching. The panel also aimed to reach consensus on 'whom to switch', 'when to switch' and 'how to switch'. The key findings from that meeting are reported in this review.

Differentiating between lewy body dementia and Alzheimer's disease: a retrospective brain bank study

Recent research has shown that while Lewy body dementia. (LBD) may be the second most common form of dementia, it is difficult to confirm the disease before autopsy. Patients with LBD share many clinical signs and symptoms with patients diagnosed with Alzheimer's disease (AD), making it difficult to differentiate between the two diseases in patients who are still living. Still, our purpose in this study was to determine any clinical features which may differentiate between autopsy-confirmed cases of AD and cases of LBD. We compared 13 patients with autopsy-confirmed AD with 12 patients who had autopsy-confirmed LBD. Phone calls were made to family members of the deceased to help clarify and add any other information not documented in the patient's files. Significant differences were found in three areas, and trends approaching statistical significance were found in two other areas. Visual hallucinations were more prominent in the patients with LBD than in the patients with AD (10/12 LBD vs. 4/13 AD, P < 0.05). A nonspecific tremor was also found more often in the LB patients than in the Alzheimer's patients (8/12 LBD vs. 3/13 AD, P < 0.05). Finally, the LB patients were more prone to wandering, especially earlier in the disease course than were the patients with AD (10/12 LBD vs. 6/13 AD, P < 0.5). There was also a trend within the LB patients for higher use of anxiolytics (9/12 LBD vs. 6/13 AD, P = 0.14) as well as antidepressants (7/12 LBD vs. 4/13 AD, P = 0.16). Our data confirmed our hypothesis that LBD from a clinical perspective is indeed similar to AD. However, the higher incidence of visual hallucinations, tremor and wandering as well as the trend toward the use of anxiolytics and antidepressants among LB patients was noted. This gives hope that a clinical differentiation between these two diseases and more specific treatments may be possible in the future.

Recognition and Management of Behavioral Disturbances in Dementia

Behavioral disturbances are seen in most patients with dementia at some point in their course. They cause immense patient suffering and are responsible for caregiver stress, institutionalization, and hospitalization. Identification of predisposing and precipitating factors is very important. The approach to the management of behavioral disturbances in dementia patients should be structured and thorough. Ensuring the safety of the patient and others should be paramount. Addressing the causes of behavioral disturbances such as comorbid medical illnesses, polypharmacy, pain, personal need, environmental factors, etc. is critical to a successful outcome. Many behavioral disturbances such as wandering and hoarding are not amenable to pharmacotherapy. Nonpharmacologic interventions are the mainstay of managing behavioral disturbances. Success of pharmacologic interventions will depend on accurate identification of specific syndromes, e.g., depression-anxiety and psychosis and severity of symptoms. Response to pharmacologic interventions is usually modest and may be associated with significant symptom resolution. Many behavioral disturbances can be prevented by avoiding inappropriate medications and educating patient, family, caregivers, and health care providers. Hospitalization can be avoided and institutionalization delayed by early recognition and treatment of behavioral disturbances. Leadership from physicians to implement preventive measures is recommended. Research to clarify the biological underpinnings of behavioral disturbances and to address cost-effectiveness of currently identified interventions is needed.

Generalized anxiety disorder in the elderly

Anxiety disorders, especially GAD, are among the most prevalent psychiatric illnesses in the elderly. Unfortunately, research relative to late-onset anxiety syndromes and longitudinal studies of early-onset anxiety syndromes are sparse. Nonetheless, clinicians can properly assess and treat older adults with anxiety disorders and improve their quality of life. Additional research is needed to better elucidate the various presentations of GAD in the elderly and in developing safe, effective, nonpharmacologic and pharmacologic treatment approaches.