Cholinesterase inhibitors -- Cochrane database review
SUMMARY
Cholinesterase inhibitors (ChEIs), donepezil, galantamine and rivastigmine are efficacious for mild to moderate Alzheimer's disease
Alzheimer's disease is the commonest cause of dementia affecting older people, and is associated with loss of cholinergic neurons in parts of the brain. Cholinesterase inhibitors (ChEIs), donepezil, galantamine and rivastigmine, delay the breakdown of acetylcholine released into synaptic clefts and so enhance cholinergic neurotransmission.
The three cholinesterase inhibitors are efficacious for mild to moderate Alzheimer's disease. Despite the slight variations in the mode of action of the three cholinesterase inhibitors there is no evidence of any differences between them with respect to efficacy. The evidence from one large trial shows fewer adverse events associated with donepezil compared with rivastigmine.
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Author: Birks J.
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Background
Since the introduction of the first cholinesterase inhibitor (ChEI) in 1997, most clinicians and probably most patients would consider the cholinergic drugs, donepezil, galantamine and rivastigmine, to be the first line pharmacotherapy for mild to moderate Alzheimer's disease.
The drugs have slightly different pharmacological properties, but they all work by inhibiting the breakdown of acetylcholine, an important neurotransmitter associated with memory, by blocking the enzyme acetylcholinesterase. The most that these drugs could achieve is to modify the clinical manifestations of Alzheimer's disease. Cochrane reviews of each ChEI for Alzheimer's disease have been completed.
Objectives
To assess the effects of donepezil, galantamine and rivastigmine in people with mild, moderate or severe dementia due to Alzheimer's disease.
Search strategy
The Cochrane Dementia and Cognitive Improvement Group's Specialized Register was searched using the terms 'donepezil', 'E2020' , 'Aricept' , galanthamin* galantamin* reminyl, rivastigmine, exelon, "ENA 713" and ENA-713 on 12 June 2005. This Register contains up-to-date records of all major health care databases and many ongoing trial databases.
Selection criteria
All unconfounded, blinded, randomized trials of at least six months in which treatment with a ChEI at the usual recommended dose was compared with placebo or another ChEI for patients with mild, moderate or severe dementia due to Alzheimer's disease.
Data collection and analysis
Data were extracted by one reviewer (JSB), pooled where appropriate and possible, and the pooled treatment effects, or the risks and benefits of treatment, estimated.
Main results
The results of 10 randomized, double blind, placebo controlled trials demonstrate that treatment for 6 months, with donepezil, galantamine or rivastigmine at the recommended dose for people with mild, moderate or severe dementia due to Alzheimer's disease produced improvements in cognitive function, on average -2.7 points (95%CI -3.0 to -2.3, p<0.00001), in the midrange of the 70 point ADAS-Cog Scale. Study clinicians rated global clinical state more positively in treated patients. Benefits of treatment were also seen on measures of activities of daily living and behaviour. None of these treatment effects are large.
The effects are similar for patients with severe dementia, although there is very little evidence, from only two trials.
More patients leave ChEI treatment groups, 29%, on account of adverse events than leave the placebo groups (18%).
There is evidence of more adverse events in total in the patients treated with a ChEI than with placebo. Although many types of adverse event were reported, nausea, vomiting, diarrhoea, were significantly more frequent in the ChEI groups than in placebo.
There is only one randomized, double blind study in which two ChEIs are compared, donepezil compared with rivastigmine.
There is no evidence of a difference between donepezil and rivastigmine for cognitive function, activities of daily living and behavioural disturbance at two years. Fewer patients suffer adverse events on donepezil than rivastigmine.
Authors' conclusions
The three cholinesterase inhibitors are efficacious for mild to moderate Alzheimer's disease. Despite the slight variations in the mode of action of the three cholinesterase inhibitors there is no evidence of any differences between them with respect to efficacy. The evidence from one large trial shows fewer adverse events associated with donepezil compared with rivastigmine.
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This is a Cochrane review abstract and plain language summary, prepared and maintained by The Cochrane Collaboration, currently published in The Cochrane Database of Systematic Reviews 2009 Issue 1, Copyright © 2009 The Cochrane Collaboration. Published by John Wiley and Sons, Ltd.. The full text of the review is available in The Cochrane Library (ISSN 1464-780X).
This record should be cited as: Birks J. Cholinesterase inhibitors for Alzheimer's disease. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005593. DOI: 10.1002/14651858.CD005593.
This version first published online: January 25. 2006
