The purpose of this research study is to learn if the medication Memantine Hydrochloride (the
study medication) can help adolescents and young adults with Down syndrome. Dr. Alberto Costa
and his research team want to see if a 16-week treatment with this medication can improve the
participant's ability to learn and remember things. In this study, memantine hydrochloride
will be used. Thus, the researchers want to learn whether the study drug can help improve
memory in young adults with Down syndrome. To test the effect of the study medicine, half of
the people in the study will receive the study medicine and half will receive a placebo (an
inactive substance). Memantine is an approved medication to treat memory and thinking
problems in persons with Alzheimer disease. However, little is known about the effect of this
medication in persons with Down syndrome and it has not been approved for use in persons with
Down syndrome.