Donepezil is a drug used for treatment of symptoms associated with Alzheimer's disease. It was approved by the US Food and Drug Administration (FDA) in 1996 and is currently marketed in the US by Pfizer under the brand name of Aricept.

Donepezil works to increase the level of acetylcholine in the brain. Acetylcholine is a neurotransmitter which is important for learning and memory; one feature of AD is a reduction in brain levels of acetylcholine. Like the other currently-available AD drugs, tacrine (trade name Cognex), rivastigmine (trade name Exelon) and galantamine (trade name Reminyl), donepezil is a cholinesterase inhibitor, meaning that it acts to inhibit the enzymes which break down unused acetylcholine; the result is that existing acetylcholine survives longer and is more effective.