Aricept (donepezil) is an oral medication used to treat the symptoms of dementia caused by Alzheimer’s disease (AD). It is marketed by Eisai in collaboration with Pfizer.

How Aricept works

Aricept is part of a class of drugs called “cholinesterase inhibitors.” It is a reversible inhibitor of an enzyme — a catalyst that can trigger a chemical reaction — called acetylcholinesterase. Acetylcholinesterase breaks down the neurotransmitter known as acetylcholine, to promote concentration of acetylcholine in the brain. (Neurotransmitters are chemical messengers produced by nerve cells to pass messages between brain cells).

AD is a progressive neurological disorder in which patients experience a progressive worsening in memory and thinking ability, due to the death of nerve cells in the brain. Acetylcholine is involved in thought processes such as memory and judgment. A reduction in the number of cells that can produce and receive acetylcholine — which amounts to a disruption in the transmission of these essential messages — could be the cause of some Alzheimer’s symptoms.

Aricept is thought to increase acetylcholine levels in the brain by preventing the breakdown of acetylcholine. This can increase the communication between remaining healthy nerve cells in the brain, and provide a temporary reprieve from dementia linked to Alzheimer’s by improving cognition and function. Aricept does not treat the underlying cause of the disease, and therefore not cure or stop its progression.

Aricept in clinical trials

Aricept has been extensively studied in clinical trials for the different stages (mild, moderate and severe) of AD. To measure changes in cognition (thinking and memory ability) and the ability to carry out daily tasks, tests such as the two-part Alzheimer’s Disease Assessment Scale (ADAS) are used. The ADAS-cognition (ADAS-cog) part measures such skills a as memory, language, and reasoning, and assigns the patient a score from 0-70 based on the level of cognitive impairment. A higher score indicates that the patient has more severe symptoms, and the score usually increases each year as the disease progresses.

Aricept was approved  by the U.S. Food and Drug Administration (FDA) in November 1996 to treat mild to moderate AD. One of the trials instrumental in this approval of the drug was published in the scientific journal Neurology. The results showed a significant improvement in ADAS-cog score in Aricept-treated patients compared to placebo, but improvements did not persist after the Aricept treatment ended, suggesting that Aricept had a positive effect on managing symptoms, but no effect on the underlying disease.

Aricept became the first treatment approved to treat all stages of AD in 2006, when its use was extended to patients with severe Alzheimer’s. The decision to cover the full spectrum of AD was based on the results of a clinical study in 248  patients with severe AD living in nursing homes, and published in the scientific journal The Lancet. This trial demonstrated a significant improvement in cognition and daily function in severe Alzheimer’s patients treated with Aricept compared to placebo.

Other information

The most common adverse effects caused by Aricept recorded in clinical trials include nausea (sickness), diarrhea, insomnia (trouble sleeping), vomiting, muscle cramps, fatigue, and anorexia (loss of appetite).

The active ingredient in Aricept is donepezil hydrochloride, and it is orally administered in the form of a tablet that dissolves on the tongue. Tablets come in 5 mg, 10 mg, and 23 mg form. Mild to moderate AD is treated with 5 mg or 10 mg per day, and moderate to severe AD is treated with the higher dose of 10 mg or 23 mg per day.

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