BACKGROUND: Alzheimer’s disease (AD) is the most commonly occurring form of dementia. It is predominantly a disease of later life, affecting 5% of those over 65 in the UK. OBJECTIVES: Review and update guidance to the NHS in England and Wales on the clinical effectiveness and cost-effectiveness of donepezil, galantamine, rivastigmine [acetylcholinesterase inhibitors (AChEIs)] and memantine within their licensed indications for the treatment of AD, which was issued in November 2006 (amended September 2007 and August 2009). DATA SOURCES: Electronic databases were searched for systematic reviews and/or metaanalyses, randomised controlled trials (RCTs) and ongoing research in November 2009 and updated in March 2010; this updated search revealed no new includable studies. The databases searched included The Cochrane Library (2009 Issue 4, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials), MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, EMBASE, PsycINFO, EconLit, ISI Web of Science Databases--Science Citation Index, Conference Proceedings Citation Index, and BIOSIS; the Centre for Reviews and Dissemination (CRD) databases--NHS Economic Evaluation Database, Health Technology Assessment, and Database of Abstracts of Reviews of Effects. REVIEW METHODS: The clinical effectiveness systematic review was undertaken following the principles published by the NHS CRD. We included RCTs whose population was people with AD. The intervention and comparators depended on disease severity, measured by the Mini Mental State Examination (MMSE). INTERVENTIONS: mild AD (MMSE 21-26)--donepezil, galantamine and rivastigmine; moderate AD (MMSE 10-20)--donepezil, galantamine, rivastigmine and memantine; severe AD (MMSE < 10)--memantine. Comparators: mild AD (MMSE 21-26)--placebo or best supportive care (BSC); moderate AD (MMSE 10-20)--donepezil, galantamine, rivastigmine, memantine, placebo or BSC; severe AD (MMSE < 10)--placebo or BSC. The outcomes were clinical, global, functional, behavioural, quality of life, adverse events, costs and cost-effectiveness. Where appropriate, data were pooled using pair-wise meta-analysis, multiple outcome measures, metaregression and mixedtreatment comparisons. The decision model was based broadly on the structure of the three-state Markov model described in the previous technology assessment report, based upon time to institutionalisation, parameterised with updated estimates of effectiveness, costs and utilities. RESULTS: Notwithstanding the uncertainty of our results, we found in the base case that the AChEIs are probably cost saving at a willingness-to-pay (WTP) of £’30,000 per qualityadjusted life-year (QALY) for people with mild-to-moderate AD. For this class of drugs, there is a > 99% probability that the AChEIs are more cost-effective than BSC. These analyses assume that the AChEIs have no effect on survival. For the AChEIs, in people with mild to moderate AD, the probabilistic sensitivity analyses suggested that donepezil is the most cost-effective, with a 28% probability of being the most cost-effective option at a WTP of £’30,000 per QALY (27% at a WTP of £’20,000 per QALY). In the deterministic results, donepezil dominates the other drugs and BSC, which, along with rivastigmine patches, are associated with greater costs and fewer QALYs. Thus, although galantamine has a slightly cheaper total cost than donepezil (£’69,592 vs £’69,624), the slightly greater QALY gains from donepezil (1.616 vs 1.617) are enough for donepezil to dominate galantamine.The probability that memantine is cost-effective in a moderate to severe cohort compared with BSC at a WTP of £’30,000 per QALY is 38% (and 28% at a WTP of £’20,000 per QALY). The deterministic ICER for memantine is £’32,100 per/QALY and the probabilistic ICER is £’36,700 per/QALY. LIMITATIONS: Trials were of 6 months maximum follow-up, lacked reporting of key outcomes, provided no subgroup analyses and used insensitive measures. Searches were limited to English language, The model does not include behavioural symptoms and there is uncertainty about the model structure and parameters. CONCLUSIONS: The additional clinical effectiveness evidence identified continues to suggest clinical benefit from the AChEIs in alleviating AD symptoms, although there is debate about the magnitude of the effect. Although there is also new evidence on the effectiveness of memantine, it remains less supportive of this drug’s use than the evidence for AChEIs. The conclusions concerning cost-effectiveness are quite different from the previous assessment. This is because both the changes in effectiveness and costs between drug use and non-drug use underlying the ICERs are very small. This leads to highly uncertain results, which are very sensitive to change. RESEARCH PRIORITIES: RCTs to include mortality, time to institutionalisation and quality of life, powered for subgroup analysis. FUNDING: The National Institute for Health Research Health Technology Assessment programme.