Donepezil Alzheimer's drug. Molecular model of the Alzheimer's drug donepezil. Atoms are represented as rods and are colour-coded: carbon (blue), hydrogen (yellow), nitrogen (dark blue) and oxygen (red). Donepezil belongs to a class of drugs known as cholinesterase inhibitors. It inhibits the enzyme acetylcholinesterase, which destroys the neurotransmitter acetylcholine. Lack of neurotransmitters is thought to play a role in Alzheimer's disease, a common cause of dementia in the elderly. Donepezil does not cure the disease, or slow its progression, but it can improve cognitive function.