Donepezil is a racemate comprising equimolar amounts of (R)- and (S)-donepezil. A centrally acting reversible acetylcholinesterase inhibitor, its main therapeutic use is in the treatment of Alzheimer's disease where it is used to increase cortical acetylcholine. It has a role as an EC 3.1.1.7 (acetylcholinesterase) inhibitor, a nootropic agent and an EC 3.1.1.8 (cholinesterase) inhibitor. It contains a (R)-donepezil and a (S)-donepezil. It is a conjugate base of a donepezil (1+).