Memantine for later stages

Memantine (Namenda) is approved by the FDA for treatment of moderate to severe Alzheimer's disease. It works by regulating the activity of glutamate, a messenger chemical widely involved in brain functions — including learning and memory. It's taken as a pill or syrup. Common side effects include dizziness, headache, confusion and agitation.

The FDA has also approved a combination of donepezil and memantine (Namzaric), which is taken as a capsule. Side effects include headache, dizziness, nausea and diarrhea.