Cholinesterase inhibitors are a class of drugs that treat neurodegenerative diseases by increasing the levels of acetylcholine in the brain: 

    What they do
    Cholinesterase inhibitors prevent the breakdown of acetylcholine, a chemical messenger that's important for learning and memory. This increases the amount of acetylcholine available to bind to receptors in the brain, which helps nerve cells communicate more effectively. 

What they're used for
Cholinesterase inhibitors are most commonly used to treat Alzheimer's disease, Parkinson's disease, and Lewy body dementia. 
How they're taken
Cholinesterase inhibitors are usually taken as tablets or capsules, but rivastigmine is also available as a patch. 
Commonly prescribed drugs
Some common cholinesterase inhibitors include: 

    Donepezil (Aricept): Approved to treat all stages of Alzheimer's disease 

Rivastigmine (Exelon): Approved for mild-to-moderate Alzheimer's and mild-to-moderate dementia associated with Parkinson's disease 
Galantamine (Razadyne): Approved for mild-to-moderate stages of Alzheimer's disease 

Side effects
Side effects of cholinesterase inhibitors can include diarrhea, nausea, vomiting, stomach pain, dizziness, headache, anxiety, blurred vision, dry mouth, and insomnia. 

While cholinesterase inhibitors are generally safe, they should only be started after an accurate specialist diagnosis