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.