Memantine is an NMDA-antagonist that is believed to block glutamate-related excitotoxicity and mitigate some of the symptoms of Alzheimer's Disease. Although research does not yet support the claim, some people claim memantine improves the cognitive abilities of healthy people. In 2005, the US FDA rejected an application to allow memantine to be prescribed to patients with mild AD, suggesting the efficacy and safety for patients without severe impairment is not yet well documented.