Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.8 (cholinesterase)
12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Diffuse Lewy body disease (DLB) is a neurodegenerative disorder characterized by dementia, fluctuations in mental status, hallucinations, and parkinsonism. Diffuse Lewy body disease is the second most common cause of dementia, following Alzheimer's disease. The treatment of DLB includes cholinergic therapy for cognitive impairment, atypical neuroleptics to alleviate hallucinations, and levodopa/carbidopa to improve parkinsonism. The recognition and diagnosis of DLB has critical treatment implications. Centrally acting cholinesterase inhibitors, such as rivastigmine, donepezil, and galantamine partially reverse decreased cortical cholinergic activity and may improve cognition and neuropsychiatric symptoms in DLB. Rivastigmine has been demonstrated to improve cognition and neuropsychiatric symptoms in patients with DLB without worsening parkinsonian features. Due to the potential adverse events associated with neuroleptics in this population, treatment with cholinesterase inhibitors is currently considered first-line therapy in the treatment of hallucinations and mental status fluctuations in DLB. Exquisite sensitivity to neuroleptic medications is a hallmark of DLB and life-threatening complications have been reported. Caution should be exercised when implementing antipsychotic therapy for the treatment of behavioral disturbances of DLB. When required, atypical neuroleptics with the least extrapyramdial side effects, such as quetiapine, should be used. The parkinsonian features of DLB may respond to dopaminergic therapy with levodopa. If parkinsonian symptoms result in clinical disability, a trial of levodopa is warranted. Unfortunately, dopaminergic medications may worsen hallucinations. Because dopamine agonists have a greater tendency to induce hallucinations and somnolence, levodopa is the treatment of choice for parkinsonism in DLB. Rapid eye movement (REM) sleep behavior disorder (RBD) is now recognized as a feature of DLB. Awareness of the presence of this symptom in patients with DLB is important and treatment with low dose clonazepam may help. Cholinergic aumentation may also improve these symptoms in patients with DLB.
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PMID:Diffuse Lewy Body Disease. 1158 27

In-vivo metabolic measures with positron emission tomography using (18)F-fluorodeoxyglucose (FDG-PET) have demonstrated hypometabolism in temporal, frontal, and hippocampal areas during the early stages of Alzheimer's disease (AD). Progression of the dementia in AD involves compromised cholinergic functioning. Cholinesterase inhibitors have demonstrated efficacy in improving cognition and behaviour in AD. In this study, we demonstrate the usefulness of FDG-PET in measuring the progression of untreated AD and its modification by treatment with rivastigmine (Exelon, Novartis Pharmaceuticals, East Hanover, New Jersey, USA), a centrally selective cholinesterase inhibitor of the carbamate type. Patients with mild to moderate probable AD (Mini-Mental Status Exam scores of 10-26, inclusive) were enrolled in a double-blind, placebo controlled comparison of three fixed daily doses of rivastigmine (3, 6, or 9 mg/d) or placebo for 26 wk. FDG-PET scans were obtained on 27 patients at baseline and following 26 wk of treatment using the Snodgrass Picture Naming activation task. A total of 71.4% of the patients treated with placebo deteriorated clinically compared to only 25.0% of the patients treated with rivastigmine (chi2 = 4.8; p & 0.03). Rivastigmine-responders (i.e. those who clinically improved or remained clinically stable as measured by the Clinicianaposs Interview-Based Impression of Change-plus) showed a marked increase in brain metabolism (p <0.01) involving, but not limited to, structures comprising the memory-related cortices and the prefrontal system. These metabolic changes were not observed in the placebo-treated patients or the rivastigmine non-responders. Of note is that responders increased hippocampal metabolism by 32.5% (p < 0.03) compared to a non-significant decrease in the non-responders (6.4%) and placebo-treated patients (4.1%). These results are consistent with the literature suggesting that FDG-PET can sensitively measure the progression of AD and its improvement with cholinesterase inhibitors. Rivastigmine prevented the expected deterioration in clinical status and dramatically increased brain metabolic activity in a majority of patients.
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PMID:Brain metabolic and clinical effects of rivastigmine in Alzheimer's disease. 1160 28

Cholinesterase inhibitors have produced the best evidence of clinical efficacy for treating patients with Alzheimer's disease (AD). Many of these drugs selectively inhibit acetylcholinesterase (AChE), but agents that also target butyrylcholinesterase (BuChE) may provide added benefits. As AD progresses, ACh regulation may become increasingly dependent on BuChE and dual inhibitors may provide more sustained efficacy than AChE-selective agents. Dual inhibition may also help to slow the formation of amyloidogenic compounds, providing an important disease-modifying mechanism. Rivastigmine is a dual inhibitor that has demonstrated benefits across the spectrum of AD severity and across the cognitive, functional and behavioural domains of AD. It is a priority for future clinical trials to determine whether agents with dual inhibition properties have greater clinical efficacy.
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PMID:Advances in the treatment of Alzheimer's disease: benefits of dual cholinesterase inhibition. 1180 98

In order to develop new cholinesterase agents effective against Alzheimer's disease (AD) we synthesized some phenylcarbamates structurally related to Rivastigmine and evaluated their in vitro and in vivo biological activity. Among the compounds which displayed the most significant in vitro activity, 1-[1-(3-dimethylcarbamoyloxyphenyl)ethyl]piperidine (31b), in addition to a simple and cheaper synthesis, showed lower toxicity and very similar therapeutic index in comparison with Rivastigmine.
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PMID:Synthesis and cholinesterase activity of phenylcarbamates related to Rivastigmine, a therapeutic agent for Alzheimer's disease. 1185 43

Rivastigmine, a carbamate inhibitor of acetylcholinesterase, is already in use for treatment of Alzheimer's disease under the trade name of Exelon. Rivastigmine carbamylates Torpedo californica acetylcholinesterase very slowly (k(i) = 2.0 M(-1) min(-1)), whereas the bimolecular rate constant for inhibition of human acetylcholinesterase is >1600-fold higher (k(i) = 3300 M(-1) min(-1)). For human butyrylcholinesterase and for Drosophila melanogaster acetylcholinesterase, carbamylation is even more rapid (k(i) = 9 x 10(4) and 5 x 10(5) M(-1) min(-1), respectively). Spontaneous reactivation of all four conjugates is very slow, with <10% reactivation being observed for the Torpedo enzyme after 48 h. The crystal structure of the conjugate of rivastigmine with Torpedo acetylcholinesterase was determined to 2.2 A resolution. It revealed that the carbamyl moiety is covalently linked to the active-site serine, with the leaving group, (-)-S-3-[1-(dimethylamino)ethyl]phenol, being retained in the "anionic" site. A significant movement of the active-site histidine (H440) away from its normal hydrogen-bonded partner, E327, was observed, resulting in disruption of the catalytic triad. This movement may provide an explanation for the unusually slow kinetics of reactivation.
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PMID:Kinetic and structural studies on the interaction of cholinesterases with the anti-Alzheimer drug rivastigmine. 1188 71

Recent health technology assessments have given us the go-ahead to use cholinesterase inhibitors, which, in combination with community services, are currently the most appropriate treatment for patients with Alzheimer's disease (AD). Initial research focused upon acetylcholinesterase (AChE)-selective agents, but it is now thought that dual inhibitors of AChE and butyrylcholinesterase (BuChE) may provide more sustained efficacy over the course of AD and may help to slow disease progression. Rivastigmine is a potent inhibitor of AChE and BuChE and has demonstrated broad benefits across the severity of AD and across the cognitive, functional and behavioural domains of AD. In addition, rivastigmine has shown cognitive and behavioural benefits in patients with dementia with the Lewy body variant of AD. These benefits may reflect the inhibition of both AChE and BuChE, as demonstrated by significant correlations between cognitive improvements and cholinesterase inhibition in rivastigmine-treated patients with AD. Rivastigmine shows a clear dose-response relationship, and physicians should aim to maintain patients on doses of 6 mg/day or higher, to a maximum of 12 mg/day. As with all cholinesterase inhibitors, rapid forced dose escalation may increase the incidence of typical cholinergic side-effects, resulting in lower maintenance doses. In a chronic disease such as AD, there is time to implement slow dose escalation and higher final maintenance doses. If used appropriately, the benefits of rivastigmine seen in clinical practice may prove to be even greater than those reported in clinical trials.
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PMID:The clinical benefits of rivastigmine may reflect its dual inhibitory mode of action: an hypothesis. 1201 28

Multiple behavioural and psychological symptoms of dementia (BPSD) are commonly associated with all dementia subtypes, and worsen during disease progression. BPSD arise due to impairment of cholinergic function in the cortex, hippocampus and related limbic systems. Recent studies have investigated the effect of cholinesterase inhibitors on BPSD. The dual acetylcholinesterase/butyrylcholinesterase (AChE/BuChE) inhibitor rivastigmine was shown to have several potential advantages over the AChE-selective inhibitors donepezil and galantamine for the treatment of BPSD. Rivastigmine appears to be effective across the range of dementia severity from mild to severe, and across the spectrum of dementia (Alzheimer's disease [AD], the AD variant with Lewy bodies, Parkinson's disease dementia and vascular dementia subtypes). It also appears to have a disease-modifying potential. Rivastigmine improved a wider range of behavioural symptoms (apathy, anxiety/depression, hallucinations and delusions) than donepezil and galantamine (which improved apathy and depression/anxiety only). Unlike donepezil, rivastigmine reduced the need for psychotropic medications to treat BPSD. Dual inhibition of AChE and BuChE and brain-region selectivity through preferential inhibition of the G1 isoform of AChE may provide the underlying reasons for the apparently greater and broader efficacy of rivastigmine over AChE-selective inhibitors for the treatment of BPSD. However, randomised, controlled trials are required to compare dual inhibitors, such as rivastigmine, and AChE-selective agents, to confirm and quantify any differences in their effects on BPSD.
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PMID:The efficacy of cholinesterase inhibitors in treating the behavioural symptoms of dementia. 1213 65

In the absence of a cure for Alzheimer's disease (AD), treatment has focused on therapy to provide symptomatic benefits and to slow progression of the disease, so that patients can maintain their independence for as long as possible. New research suggests that rivastigmine, a potent, pseudo-irreversible inhibitor of both acetylcholinesterase (AChE) and butyrylcholinesterase that shows preferential selectivity for the G1 form of AChE, may provide symptomatic and disease progression slowing effects. The drug's pharmacological properties may help to slow the conversion of diffuse, benign amyloid plaques to neuritic plaques associated with clinical dementia. In 'delayed-start' paradigms--open-label extensions of placebo-controlled studies involving mild to moderate AD patients--the treatment effects of rivastigmine on cognitive and non-cognitive outcomes at 52 weeks were even greater than those observed at 26 weeks, and patients who received rivastigmine for the entire 52 weeks had better outcomes than those who received rivastigmine only for the latter 26 weeks (having received placebo for the first 26 weeks during the placebo-controlled phase). These treatment effects were even more robust in patients with moderately severe disease, indicating that the sustained long-term benefits of rivastigmine apply across the continuum of disease severity. The results seen in those patients with mild and moderately severe AD suggest that the progression of AD was being slowed in treated patients and that a disease-modifying effect may have been taking place. The effects of rivastigmine on cognition remain clinically relevant for at least 2 years, with benefits over projected placebo increasing over time. The long-term benefits of rivastigmine have also been reported in behavioural domains of patients with mild to moderate AD for 104 weeks and in patients with the Lewy body variant of AD for 96 weeks. Rivastigmine may slow AD progression, allowing patients to maintain autonomy for longer.
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PMID:Do cholinesterase inhibitors slow progression of Alzheimer's disease? 1213 66

Despite recognition that cholinesterase inhibitors can provide clinical benefits for patients with Alzheimer's disease (AD), the average durations of treatment and beneficial effects are not optimal in all cases. This may be due to disappointing efficacy or poor tolerability of the initial treatment, as well as secondary efficacy failure or adverse effects emerging during the maintenance phase. In such cases, pharmacological differences between available cholinesterase inhibitors provide a good rationale to switch to another drug in the same class. The pharmacological properties of rivastigmine, a dual inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase, and donepezil and galantamine, two AChE-selective inhibitors, are reviewed. Rivastigmine is reported to show brain- and brain region-selectivity. Donepezil appeared to be more selective for central than peripheral enzymes in rats. Galantamine and donepezil have also been shown to exert nicotinic receptor allosteric modulation in vitro, while rivastigmine has been shown to increase binding of acetylcholine to nicotinic receptors in the AD brain. Donepezil and galantamine are metabolised by the hepatic CYP450 system, whereas rivastigmine is metabolised by its target enzymes. Several switching studies indicated that a substantial proportion of patients who fail to benefit from treatment with donepezil could draw benefits after being switched to rivastigmine. An immediate switch from donepezil to rivastigmine was reported to be well tolerated and was not associated with cholinergic side effects. A post hoc analysis of a 5-month trial with galantamine showed that patients had similar efficacy outcomes, whether or not they had received prior anticholinesterase therapy, suggesting that a previous failure to respond to another cholinesterase inhibitor did not predict response to galantamine. On the basis of available data it is suggested that patients not tolerating or not responding to one particular cholinesterase inhibitor may still draw benefits upon switching to another.
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PMID:Switching cholinesterase inhibitors in patients with Alzheimer's disease. 1213 69

Cholinesterase inhibitors are the 'first-line' agents in the treatment of Alzheimer's disease. This article presents the latest information on their pharmacokinetic properties and pharmacodynamic activity. Tacrine was the first cholinesterase inhibitor approved by regulatory agencies, followed by donepezil, rivastigmine and recently galantamine. With the exception of low doses of tacrine, the cholinesterase inhibitors exhibit a linear relationship between dose and area under the plasma concentration-time curve. Cholinesterase inhibitors are rapidly absorbed through the gastrointestinal tract, with time to peak concentration usually less than 2 hours; donepezil has the longest absorption time of 3 to 5 hours. Donepezil and tacrine are highly protein bound, whereas protein binding of rivastigmine and galantamine is less than 40%. Tacrine is metabolised by hepatic cytochrome P450 (CYP) 1A2, and donepezil and galantamine are metabolised by CYP3A4 and CYP2D6. Rivastigmine is metabolised by sulfate conjugation. Two cholinesterase enzymes are present in the body, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Tacrine and rivastigmine inhibit both enzymes, whereas donepezil and galantamine specifically inhibit AChE. Galantamine also modulates nicotine receptors, thereby enhancing acetylcholinergic activity at the synapse. These different pharmacological profiles provide distinctions between these agents. Cholinesterase inhibitors show a nonlinear relationship between dose and cholinesterase inhibition, where a plateau effect occurs. Cholinesterase inhibitors display a different profile as each agent achieves its plateau at different doses. In clinical trials, cholinesterase inhibitors demonstrate a dose-dependent effect on cognition and functional activities. Improvement in behavioural symptoms also occurs, but without a dose-response relationship. Gastrointestinal adverse events are dose-related. Clinical improvement occurs with between 40 and 70% inhibition of cholinesterase. A conceptual model for cholinesterase inhibitors has been proposed, linking enzyme inhibition, clinical efficacy and adverse effects. Currently, measurement of enzyme inhibition is used as the biomarker for cholinesterase inhibitors. New approaches to determining the efficacy of cholinesterase inhibitors in the brain could involve the use of various imaging techniques. The knowledge base for the pharmacokinetics and pharmacodynamics of cholinesterase inhibitors continues to expand. The increased information available to clinicians can optimise the use of these agents in the management of patients with Alzheimer's disease.
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PMID:Clinical pharmacokinetics and pharmacodynamics of cholinesterase inhibitors. 1216 59


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