Translation from Preclinical Research to Clinical Trials: Transdermal Drug Delivery for Neurodegenerative and Mental Disorders

Neurodegenerative diseases (NDs), particularly dementia, provide significant problems to worldwide healthcare systems. The development of therapeutic materials for various diseases has a severe challenge in the form of the blood-brain barrier (BBB). Transdermal treatment has recently garnered widespread favor as an alternative method of delivering active chemicals to the brain. This approach has several advantages, including low invasiveness, self-administration, avoidance of first-pass metabolism, preservation of steady plasma concentrations, regulated release, safety, efficacy, and better patient compliance. Topics include the transdermal method for therapeutic NDs, their classification, and the mechanisms that allow the medicine to enter the bloodstream through the skin. The paper also discusses the obstacles and potential outcomes of transdermal therapy, emphasizing the benefits and drawbacks of different approaches.

Drug Delivery Systems as a Strategy to Improve the Efficacy of FDA-Approved Alzheimer's Drugs

Alzheimer's disease (AD) is the most common form of dementia, with a high impact worldwide, accounting for more than 46 million cases. The continuous increase of AD demands the fast development of preventive and curative therapeutic strategies that are truly effective. The drugs approved for AD treatment are classified into acetylcholinesterase inhibitors and N-methyl-D-aspartate receptor antagonists. The therapeutic effectiveness of those drugs is hindered by their restricted access to the brain due to the blood-brain barrier, low bioavailability, and poor pharmacokinetic properties. In addition, the drugs are reported to have undesirable side effects. Several drug delivery systems (DDSs) have been widely exploited to address these issues. DDSs serve as drug carriers, combining the ability to deliver drugs locally and in a targeted manner with the ability to release them in a controlled and sustained manner. As a result, the pharmacological therapeutic effectiveness is raised, while the unwanted side effects induced by the unspecific distribution decrease. This article reviews the recently developed DDSs to increase the efficacy of Food and Drug Administration-approved AD drugs.

Polymeric Microneedles for Transdermal Delivery of Rivastigmine: Design and Application in Skin Mimetic Model

In the last years, microneedles (MNs) have been considered a valuable, painless, and minimally invasive approach for controlled transdermal drug delivery (TDD). Rivastigmine (RV), a drug administered to patients suffering from dementia, is currently delivered by oral or transdermal routes; however, both present limitations, mainly gastrointestinal adverse symptoms or local skin irritation and drug losses, respectively, for each route. Given this, the objective of the present work was to develop and evaluate the potential of polymeric MNs for RV transdermal delivery in a controlled manner. Polymeric MNs with two needle heights and different compositions were developed with calcein as a fluorescent model molecule. Morphology and mechanical characterisation were accessed. Skin permeation experiments showed the ability of the devices to deliver calcein and confirmed that the arrays were able to efficiently pierce the skin. To obtain a new TDD anti-dementia therapeutic solution, RV was loaded in 800 µm polymeric MNs of alginate and alginate/k-carrageenan MNs. In the presence of RV, the MN’s morphology was maintained; however, the presence of RV influenced the compression force. Skin permeation studies revealed that RV-loaded MNs allowed a more efficient controlled release of the drug than the commercial patch. In vivo, skin irritation tests in rabbits revealed that the developed MNs were innocuous upon removal, in contrast with the evidence found for Exelon^®, the commercial patch, which caused slight mechanical damage to the skin. The herein-produced MNs demonstrated a more controlled release of the drug, being the more suitable option for the transdermal delivery of RV.

Factors Affecting Rapid Cognitive Decline in Patients with Alzheimer's Disease: A Longitudinal Follow-Up Study

We investigated the preventive and risk factors of rapid cognitive decline in patients with Alzheimer’s disease (AD). Using the Chang Gung Research Database (CGRD), we enrolled patients with AD aged over 65 years between 1 January 2001 and 30 May 2019, and followed up for at least two years. Rapid cognitive decline was defined by a Mini-Mental State Examination (MMSE) score decline of ≥4 in 2 years. A longer prescription of acetylcholinesterase inhibitors (AChEIs) was defined as 22 months based on the median treatment duration of the cohorts. The Cox proportional hazards regression model adjusted for age, sex, medication, and physical comorbidities was used to examine the candidate risk and protective factors. We analyzed data from 3846 patients with AD (1503 men, 2343 women) with a mean age and percentage of females of 77.8 ± 6.2 years and 60.9%, respectively. The mean duration of patients with AD receiving AChEIs was 658.7 ± 21.9 days. In general, 310 patients with AD showed a rapid cognitive decline, accounting for 8.1%. Treatment of a consecutive AChEI prescription for >22 months in patients with AD was a protective factor against rapid cognitive decline (adjusted hazard ratio (aHR) = 0.41, 95% confidence interval (CI) = 0.33–0.52, p < 0.001). Patients with AD aged >85 years (aHR = 0.53, 95% CI = 0.36–0.79, p < 0.01) and aged 75–85 years (aHR = 0.73, 95% CI = 0.57–0.93, p < 0.05) had a significantly lower risk of rapid cognitive decline than those aged 65–75 years. Additionally, patients with mild and moderate AD (clinical dementia rating (CDR = 1, aHR = 1.61, 95% CI = 1.26–2.07, p < 0.001; CDR = 2, aHR = 2.64, 95% CI = 1.90–3.65, p < 0.001) were more likely to have rapid cognitive decline than those with early AD (CDR = 0.5). Sex, medication with different types of AChEIs, and physical comorbidities were not associated with rapid cognitive decline. These findings indicate that it is important to maintain longer consecutive AChEI prescriptions in patients with AD to prevent cognitive decline.

The Alzheimer patient from the dermatologist's point of view

Alzheimer's disease (AD) is characterized by a cluster of signs and symptoms that include memory loss, language disturbances, psychological and psychiatric changes and difficulty in carrying out daily activities. Although it may seem to be far from a dermatologic competence, the ageing of populations in industrialized and developing countries has changed things, making AD a multidisciplinary question. Indeed, this neurodegenerative disorder is not exclusively neurological, but rather may involve multiple tissues and organs. The abnormalities in metabolic and biochemical processes described in affected brains are also present in the skin and may condition specific dermatological manifestations. In fact, although a history of non-melanoma skin cancer is linked to a significantly reduced risk of developing AD, this is not so for melanoma. Several biological, social and environmental hypotheses can be advanced to explain these correlations. AD patients' memory problems and the partial inability to express an informed consent, could make a simple tumor excision challenging for a dermatologic surgeon. Moreover, attention should also be paid to the possibility of pharmacological interactions with AD therapies and to surgery timing. Observational studies have provided evidence for a non-spurious correlation between bullous pemphigoid (BP) and dementia. The demonstration of neurological isoforms of both BP180 and BP230 in the central nervous system has provided partial explanations for these findings and raised the question as to whether AD patients should be given accurate screening for BP and vice versa. Some adverse skin reactions have been observed with AD drugs and although mainly localized others are diffuse. Importantly, some of these drugs are available for administration in a patch or systemic form. When dealing with bedridden patients, the skin examination should be as complete as possible, since ulcer location is not only influenced by pressure and paratonia but also by spasticity, conditioning wounds in atypical sites.

An update on the safety of current therapies for Alzheimer's disease: focus on rivastigmine

Alzheimer's disease (AD) is the most common cause of major neurocognitive disorders worldwide. Despite all research efforts, therapeutic options for AD are still limited to two drug classes: cholinesterase inhibitors (ChEIs) and the NMDA-receptor antagonist memantine. Donepezil, rivastigmine and galantamine are the three ChEIs FDA-approved as first-line treatment for AD. Although they share the same mode of action, they differ in terms of their pharmacologic characteristics and route of administration, which can impact their safety and tolerability profile. Rivastigmine, available in both oral and transdermal patch formulations, is a slowly reversible dual inhibitor of acetyl and butyryl cholinesterase, selective for the G1 isoform of acetylcholinesterase, without hepatic metabolism by the CYP-450 system. Despite its unique features, it has been associated with a higher incidence of adverse events in comparison to other ChEIs. The oral form, approved for the treatment of mild to moderate AD, is associated with a higher incidence of gastrointestinal side effects. The transdermal patch formulation approved for use across all stages of AD has been shown to have a better tolerability profile in comparison to both the oral form and even other ChEIs. One important tolerability concern is adverse dermatologic reactions, which are mostly benign, and can be either preventable or manageable. One important safety concern is the risk of treatment overdose by administering multiple patches at the same time, potentially leading to fatal outcomes. This can be prevented by educating patients and caregivers about the proper use of the patch. The goal for the future would be to optimize the patch formulation to increase both efficacy and safety.

Pharmacotherapy for Dementia: A Practical Approach to the Use of Cholinesterase Inhibitors and Memantine

Cholinesterase inhibitors and memantine are the only classes of drugs approved for the treatment of dementia due to Alzheimer's disease. This article provides evidence-based recommendations to address the issues regarding the use of cholinesterase inhibitors and memantine in clinical practice. It includes their efficacy, timing, assessment, use in institutionalized patients, combined use, and use in other dementia types. However, most of the studies are of short duration (<1 year) and are mainly focused on cognitive and global improvement, whereas the practical issue of their use in daily practice such as optimal duration of treatment, long-term efficacy and delaying institutionalization are limited.

Acetylcholinesterase inhibitors for treating dementia symptoms - a safety evaluation

INTRODUCTION

The prevalence of Alzheimer's disease (AD) continues to rise, while treatment options for cognitive impairment are limited. Acetylcholinesterase inhibitors (AChEIs) aim to provide symptomatic benefit for cognitive decline, however these drugs are not without adverse events (AEs). The safety profile of each drug must be taken carefully into consideration before being prescribed, as new dosages and formulations have recently been approved. Areas covered: Donepezil, galantamine and rivastigmine are the three AChEIs approved for the treatment of varying stages of AD. Numerous clinical trials and post-marketing studies have evaluated the safety of these medications. This article will review the safety, efficacy and tolerability of these drugs in treating AD. Topics including pharmacovigilance databases, concomitant drug interactions, prescribing cascades, and treatment discontinuation are also covered. Expert opinion: AChEI use in those with mild, moderate or severe AD provide modest improvements in cognition, function and behavior. The pharmacological treatment of AD using AChEIs is associated with generally mild AEs. Differences in drug formulations should be taken into account when determining the most appropriate route of administration for each individual. Furthermore, discontinuation of AChEIs must be carefully monitored as it may be associated with worsening cognitive impairment.

Rivastigmine for Alzheimer's disease

BACKGROUND

Alzheimer's disease is the commonest cause of dementia affecting older people. One of the therapeutic strategies aimed at ameliorating the clinical manifestations of Alzheimer's disease is to enhance cholinergic neurotransmission in the brain by the use of cholinesterase inhibitors to delay the breakdown of acetylcholine released into synaptic clefts. Tacrine, the first of the cholinesterase inhibitors to undergo extensive trials for this purpose, was associated with significant adverse effects including hepatotoxicity. Other cholinesterase inhibitors, including rivastigmine, with superior properties in terms of specificity of action and lower risk of adverse effects have since been introduced. Rivastigmine has received approval for use in 60 countries including all member states of the European Union and the USA.

OBJECTIVES

To determine the clinical efficacy and safety of rivastigmine for patients with dementia of Alzheimer's type.

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group Specialized Register, on 2 March 2015 using the terms: Rivastigmine OR  exelon OR ENA OR "SDZ ENA 713". ALOIS contains records of clinical trials identified from monthly searches of a number of major healthcare databases (Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS), numerous trial registries and grey literature sources.

SELECTION CRITERIA

We included all unconfounded, double-blind, randomised, controlled trials in which treatment with rivastigmine was administered to patients with dementia of the Alzheimer's type for 12 weeks or more and its effects compared with those of placebo in a parallel group of patients, or where two formulations of rivastigmine were compared.

DATA COLLECTION AND ANALYSIS

One review author (JSB) applied the study selection criteria, assessed the quality of studies and extracted data.

MAIN RESULTS

A total of 13 trials met the inclusion criteria of the review. The trials had a duration of between 12 and 52 weeks. The older trials tested a capsule form with a dose of up to 12 mg/day. Trials reported since 2007 have tested continuous dose transdermal patch formulations delivering 4.6, 9.5 and 17.7 mg/day.Our main analysis compared the safety and efficacy of rivastigmine 6 to 12 mg/day orally or 9.5 mg/day transdermally with placebo.Seven trials contributed data from 3450 patients to this analysis. Data from another two studies were not included because of a lack of information and methodological concerns. All the included trials were multicentre trials and recruited patients with mild to moderate Alzheimer's disease with a mean age of about 75 years. All had low risk of bias for randomisation and allocation but the risk of bias due to attrition was unclear in four studies, low in one study and high in two studies.After 26 weeks of treatment rivastigmine compared to placebo was associated with better outcomes for cognitive function measured with the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) score (mean difference (MD) -1.79; 95% confidence interval (CI) -2.21 to -1.37, n = 3232, 6 studies) and the Mini-Mental State Examination (MMSE) score (MD 0.74; 95% CI 0.52 to 0.97, n = 3205, 6 studies), activities of daily living (SMD 0.20; 95% CI 0.13 to 0.27, n = 3230, 6 studies) and clinician rated global impression of changes, with a smaller proportion of patients treated with rivastigmine experiencing no change or a deterioration (OR 0.68; 95% CI 0.58 to 0.80, n = 3338, 7 studies).Three studies reported behavioural change, and there were no differences compared to placebo (standardised mean difference (SMD) -0.04; 95% CI -0.14 to 0.06, n = 1529, 3 studies). Only one study measured the impact on caregivers using the Neuropsychiatric Inventory-Caregiver Distress (NPI-D) scale and this found no difference between the groups (MD 0.10; 95% CI -0.91 to 1.11, n = 529, 1 study). Overall, participants who received rivastigmine were about twice as likely to withdraw from the trials (odds ratio (OR) 2.01, 95% CI 1.71 to 2.37, n = 3569, 7 studies) or to experience an adverse event during the trials (OR 2.16, 95% CI 1.82 to 2.57, n = 3587, 7 studies).

AUTHORS' CONCLUSIONS

Rivastigmine (6 to 12 mg daily orally or 9.5 mg daily transdermally) appears to be beneficial for people with mild to moderate Alzheimer's disease. In comparisons with placebo, better outcomes were observed for rate of decline of cognitive function and activities of daily living, although the effects were small and of uncertain clinical importance. There was also a benefit from rivastigmine on the outcome of clinician's global assessment. There were no differences between the rivastigmine group and placebo group in behavioural change or impact on carers. At these doses the transdermal patch may have fewer side effects than the capsules but has comparable efficacy. The quality of evidence is only moderate for all of the outcomes reviewed because of a risk of bias due to dropouts. All the studies with usable data were industry funded or sponsored. This review has not examined economic data.

Rivastigmine for Alzheimer's disease

BACKGROUND

Alzheimer's disease is the commonest cause of dementia affecting older people. One of the therapeutic strategies aimed at ameliorating the clinical manifestations of Alzheimer's disease is to enhance cholinergic neurotransmission in the brain by the use of cholinesterase inhibitors to delay the breakdown of acetylcholine released into synaptic clefts. Tacrine, the first of the cholinesterase inhibitors to undergo extensive trials for this purpose, was associated with significant adverse effects including hepatotoxicity. Other cholinesterase inhibitors, including rivastigmine, with superior properties in terms of specificity of action and lower risk of adverse effects have since been introduced. Rivastigmine has received approval for use in 60 countries including all member states of the European Union and the USA.

OBJECTIVES

To determine the clinical efficacy and safety of rivastigmine for patients with dementia of Alzheimer's type.

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group Specialized Register, on 2 March 2015 using the terms: Rivastigmine OR  exelon OR ENA OR "SDZ ENA 713". ALOIS contains records of clinical trials identified from monthly searches of a number of major healthcare databases (Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS), numerous trial registries and grey literature sources.

SELECTION CRITERIA

We included all unconfounded, double-blind, randomised, controlled trials in which treatment with rivastigmine was administered to patients with dementia of the Alzheimer's type for 12 weeks or more and its effects compared with those of placebo in a parallel group of patients, or where two formulations of rivastigmine were compared.

DATA COLLECTION AND ANALYSIS

One review author (JSB) applied the study selection criteria, assessed the quality of studies and extracted data.

MAIN RESULTS

A total of 13 trials met the inclusion criteria of the review. The trials had a duration of between 12 and 52 weeks. The older trials tested a capsule form with a dose of up to 12 mg/day. Trials reported since 2007 have tested continuous dose transdermal patch formulations delivering 4.6, 9.5 and 17.7 mg/day.Our main analysis compared the safety and efficacy of rivastigmine 6 to 12 mg/day orally or 9.5 mg/day transdermally with placebo.Seven trials contributed data from 3450 patients to this analysis. Data from another two studies were not included because of a lack of information and methodological concerns. All the included trials were multicentre trials and recruited patients with mild to moderate Alzheimer's disease with a mean age of about 75 years. All had low risk of bias for randomisation and allocation but the risk of bias due to attrition was unclear in four studies, low in one study and high in two studies.After 26 weeks of treatment rivastigmine compared to placebo was associated with better outcomes for cognitive function measured with the Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) score (mean difference (MD) -1.79; 95% confidence interval (CI) -2.21 to -1.37, n = 3232, 6 studies) and the Mini-Mental State Examination (MMSE) score (MD 0.74; 95% CI 0.52 to 0.97, n = 3205, 6 studies), activities of daily living (SMD 0.20; 95% CI 0.13 to 0.27, n = 3230, 6 studies) and clinician rated global impression of changes, with a smaller proportion of patients treated with rivastigmine experiencing no change or a deterioration (OR 0.68; 95% CI 0.58 to 0.80, n = 3338, 7 studies).Three studies reported behavioural change, and there were no differences compared to placebo (standardised mean difference (SMD) -0.04; 95% CI -0.14 to 0.06, n = 1529, 3 studies). Only one study measured the impact on caregivers using the Neuropsychiatric Inventory-Caregiver Distress (NPI-D) scale and this found no difference between the groups (MD 0.10; 95% CI -0.91 to 1.11, n = 529, 1 study). Overall, participants who received rivastigmine were about twice as likely to withdraw from the trials (odds ratio (OR) 2.01, 95% CI 1.71 to 2.37, n = 3569, 7 studies) or to experience an adverse event during the trials (OR 2.16, 95% CI 1.82 to 2.57, n = 3587, 7 studies).

AUTHORS' CONCLUSIONS

Rivastigmine (6 to 12 mg daily orally or 9.5 mg daily transdermally) appears to be beneficial for people with mild to moderate Alzheimer's disease. In comparisons with placebo, better outcomes were observed for rate of decline of cognitive function and activities of daily living, although the effects were small and of uncertain clinical importance. There was also a benefit from rivastigmine on the outcome of clinician's global assessment. There were no differences between the rivastigmine group and placebo group in behavioural change or impact on carers. At these doses the transdermal patch may have fewer side effects than the capsules but has comparable efficacy. The quality of evidence is only moderate for all of the outcomes reviewed because of a risk of bias due to dropouts. All the studies with usable data were industry funded or sponsored. This review has not examined economic data.

Rotigotine transdermal patch in Parkinson's disease: a systematic review and meta-analysis

Background and Methods

The efficacy and safety of rotigotine transdermal patch in Parkinson’s disease (PD) were studied in some clinical trials. We performed a systematic review and meta-analysis of randomized controlled trials to evaluate the efficacy, tolerability, and safety of rotigotine transdermal patch versus placebo in PD.

Results

Six randomized controlled trials (1789 patients) were included in this meta-analysis. As compared with placebo, the use of rotigotine resulted in greater improvements in Unified Parkinson’s Disease Rating Scale activities of daily living score (weighted mean difference [WMD] –1.69, 95% confidence interval [CI] –2.18 to –1.19), motor score (WMD –3.86, 95% CI –4.86 to –2.86), and the activities of daily living and motor subtotal score (WMD –4.52, 95% CI –5.86 to –3.17). Rotigotine was associated with a significantly higher rate of withdrawals due to adverse events (relative risk [RR] 1.82, 95% CI 1.29–2.59), and higher rates of application site reactions (RR 2.92, 95% CI 2.29–3.72), vomiting (RR 5.18, 95% CI 2.25–11.93), and dyskinesia (RR 2.52, 95% CI 1.47–4.32) compared with placebo. No differences were found in the relative risks of headache, constipation, back pain, diarrhea, or serious adverse events.

Conclusions

Our meta-analysis showed that the use of rotigotine can reduce the symptoms of PD. However, rotigotine was also associated with a higher incidence of adverse events, especially application site reactions, compared with placebo.

From high doses of oral rivastigmine to transdermal rivastigmine patches: user experience and satisfaction among caregivers of patients with mild to moderate Alzheimer disease

INTRODUCTION

Rivastigmine, a treatment for mild to moderate Alzheimer disease (AD), is the first cholinesterase inhibitor to be available in the transdermal format. We aim to describe user experience and satisfaction with the rivastigmine patch, as well as any clinical changes perceived in patients.

METHODS

Observational, cross-sectional, multicentre study with 239 investigators and 1851 informal caregivers of patients with mild to moderate AD. Patients were treated with transdermal rivastigmine patches for ≥ 6 months and had previously received high doses of oral rivastigmine.

RESULTS

Mean caregiver age was 59.8±14.4 years and 70.9% were women. They spent 10.0±7.1hours per day providing care and 79.8% lived with the patient. Patch instructions were described as easy to follow by 97.1% of the caregivers and 92.1% of them rated patch application as easy or very easy. The most commonly cited disadvantage was adhesion problems (26.8%). Discontinuation of treatment was due to cutaneous reactions in most cases. Overall, 76.5% of the caregivers were satisfied or very satisfied with transdermal treatment and 77.4% considered that its interference with daily activities was minimal or null. The patch was preferred to oral treatment by 94.3% of caregivers. Clinical Global Impression of Change ratings improved according to 61.3% of the caregivers and 53% of the investigators. Few caregivers reported medication forgetfulness.

CONCLUSIONS

Most caregivers of patients with mild to moderate AD preferred the transdermal format of rivastigmine to the oral format. Caregivers also reported overall satisfaction, ease of use, and reduced impact on daily activities for transdermal rivastigmine format, in addition to patient improvement compared to their condition under the previous treatment.

Rivastigmine patch for treatment of Alzheimer's disease in clinical practice in Thailand

BACKGROUND

Rivastigmine is a cholinesterase inhibitor for treatment of mild to moderate Alzheimer's disease (AD) and dementia associated with Parkinson's disease. The new patch formulation was recently made available. We assessed the safety, tolerability, and cognitive outcome of rivastigmine patch in treatment of mild to moderate AD in clinical practice in Thailand.

METHODS

A multicentre, hospital-based, prospective observational study was conducted in nine hospitals across Thailand. Patients with probable mild to moderate AD who received the rivastigmine patch were enrolled. Data were collected data at baseline, weeks 4-8 and after week16.

RESULTS

A total of 116 AD patients were screened, and three were excluded. Of 113 patients, 62.8% were women with a mean age of 73.3 ± 9.2 years; 79.7% were newly diagnosed. One-third of all patients had been using antipsychotic or antidepressant medication. Common comorbidities were hypertension and dyslipidemia. The Thai Mental State Examination score significantly increased from 18.6 to 20.3 (weeks 4-8) and 20.4 (week 16+) (P < 0.001). Scores based on physicians' (Clinical Global Impression) and caregivers' (Patients' Caregiver Global Impression of Change) impressions of improvement suggested minimal improvement. Because of adverse events, seven patients's dosages were reduced 10 cm(2) to 5 cm(2) or from 5 cm(2) to nothing. Itching was the most common adverse symptom.

CONCLUSIONS

During the first 16 weeks after initiation of rivastigmine patch therapy, patients with probable mild to moderate AD had statistically significant improvement in cognitive function, but clinically marginal benefit. Rivastigmine was safe and well tolerated.

Spotlight on rivastigmine transdermal patch: in dementia of the Alzheimer's type

Rivastigmine, a cholinesterase inhibitor, is available as a transdermal patch (Exelon® patch, Rivastach® patch, Prometax® patch) for the treatment of mild to moderate Alzheimer's disease. Rivastigmine transdermal patch was effective, in terms of improving cognitive and global function, and generally well tolerated in patients with mild to moderate dementia of the Alzheimer's type in a large, well designed trial. Most adverse events associated with rivastigmine patch were mild to moderate in severity, with the patch generally better tolerated than oral rivastigmine, especially in terms of cholinergic gastrointestinal adverse events. The patch also had good skin adhesion and a favourable skin tolerability profile in this study, with most application-site reactions being mild in severity. Additionally, in a safety and tolerability study, rivastigmine patch, regardless of concomitant memantine therapy, was generally well tolerated in patients switching from oral donepezil therapy. Thus, current evidence suggests that rivastigmine transdermal patch is an effective treatment option for patients with Alzheimer's disease, with the potential for improving compliance and providing sustained clinical benefit because of its ease of use and generally favourable tolerability profile.

Cognitive Enhancers in Moderate to Severe Alzheimer's Disease

The treatment of moderate to severe Alzheimer's disease is reviewed with regard to mechanisms of action, pharmacokinetics, metabolism, safety/tolerability, and efficacy in reducing cognitive, behavioral/psychiatric, functional and global symptoms. The cholinesterase inhibitors donepezil, rivastigmine and galantamine and the N-methyl-d-aspartate receptor channel blocker memantine are moderately beneficial. Small improvements over a few months are followed by slowed mental decline. Concerning cognitive, functional and global functions, these drugs are similarly effective. Cholinesterase inhibitors also reduce apathy, memantine counteracts agitation and aggression. Serious adverse effects are rare with all four drugs. Cholinesterase inhibitors bear a risk for patients with cardiac diseases. Adverse emetic events are typical for oral formulations of these drugs, but less for rivastigmine transdermal patches. Other routes of administration and use of a galantamine prodrug are currently investigated. The superiority of combination therapies over monotherapies requires further support. Promising investigational drugs include the copper/zinc ionophore PBT2 and multifunctional hybrid molecules.