Donepezil (Aricept) and memantine (Namenda) are both used to treat dementia related to Alzheimer's disease, but they have some key differences. Donepezil is a cholinesterase inhibitor that is FDA-approved for all stages of Alzheimer's, while memantine is an NMDA antagonist approved only for moderate-to-severe stages. Donepezil works by preventing the breakdown of acetylcholine, a chemical important for memory and learning, whereas memantine slows down overly active chemical messengers to prevent nerve damage. Donepezil is typically taken once daily at night, while memantine can be taken once or twice daily depending on the form. Common side effects of donepezil include nausea, diarrhea, and headaches, while memantine may cause dizziness, headaches, and confusion. Both medications are available in generic forms and can be taken together as a combination medication called Namzaric.