Description:

Memantine is a medication used to treat moderate-to-severe Alzheimer's disease. It is less preferred than acetylcholinesterase inhibitors such as donepezil. Treatment should only be continued if beneficial effects are seen. It is taken by mouth.
Memantine was approved for medical use in the United States in 2003. It is available as a generic medication. In 2017, it was the 149th most commonly prescribed medication in the United States, with more than four million prescriptions

Function:
 

Memantine is used to treat moderate-to-severe Alzheimer's disease, especially for people who are intolerant of or have a contraindication to AChE (acetylcholinesterase) inhibitors.One guideline recommends memantine or an AChE inhibitor be considered in people in the early-to-mid stage of dementia.

Memantine has been associated with a modest improvement; with small positive effects on cognition, mood, behavior, and the ability to perform daily activities in moderate-to-severe Alzheimer's disease. There does not appear to be any benefit in mild disease.

Memantine when added to donepezil in those with moderate-to-severe dementia resulted in "limited improvements" in a 2017 review. The UK National Institute of Clinical Excellence (NICE) issued guidance in 2018 recommending consideration of the combination of memantine with donepezil in those with moderate-to-severe dementia. Effects in autism are unclear. Recent scientific journal reports are showing guarded promise with severe obsessive compulsive disorder.