Known brand names include Aricept.
A once-daily tablet or orally disintegrating tablet for dementia of the Alzheimer type, at mild, moderate, or severe stages. It blocks the enzyme that breaks down acetylcholine, a chemical messenger in the brain, which can ease symptoms but has not been shown to change the course of the disease.
Acetylcholine is a chemical messenger that nerve cells use to pass signals, and some memory and thinking problems in Alzheimer's disease are thought to come from too little of it. Donepezil blocks acetylcholinesterase, the enzyme that normally breaks acetylcholine down. With the enzyme blocked, more acetylcholine stays available, which is believed to strengthen signaling between nerve cells. The block is reversible rather than permanent.
It leaves the body slowly, taking about 70 hours to clear half of it, so levels build up and settle only after about 15 days. The liver breaks much of it down, and part of it leaves unchanged in the urine. The same rise in acetylcholine affects the gut, heart, and stomach, which explains its main risks: nausea, vomiting, and diarrhea, a slow heartbeat or fainting, and more stomach acid that can raise the chance of ulcers and bleeding. Stomach upset is most likely when starting or raising the dose and often fades with time.
Donepezil treats dementia caused by Alzheimer's disease, a brain disease that slowly harms memory, thinking, and behavior. It has been shown to help people at the mild, moderate, and severe stages of the disease. It controls symptoms but does not cure the disease, and there is no evidence that it slows the disease itself.
It is taken by mouth once a day in the evening, just before bed, as a regular tablet or as a tablet that melts on the tongue. It can be taken with or without food. Alzheimer's disease mostly affects people over 55, and the average age of people in its studies was 73. Its safety and effectiveness have not been established in children.
Nausea, diarrhea, vomiting, trouble sleeping, muscle cramps, tiredness, and loss of appetite are the most common effects, and they often fade with continued use. The label warns that it can slow the heart or block its electrical signals, which can cause fainting. It also warns about stomach ulcers and bleeding, weight loss at the highest dose, trouble emptying the bladder, seizures, and breathing problems in people with asthma or other lung disease. It can also strengthen the effect of certain muscle relaxants used during anesthesia.