Of the many causes of dementia, Alzheimer disease (AD) is the most common. Diagnosis is generally followed by treatment. One of the most common treatments of AD is a type of medication called acetylcholinesterase inhibitors (ChEIs). ChEIs work by blocking the breakdown of a chemical in the brain called acetylcholine. In doing so, the medication allows more of this chemical to be available in the brain. This can improve or maintain cognition and memory.