The document discusses three drugs used to treat Alzheimer's disease: memantine, rivastigmine, and donepezil. Memantine is indicated for treatment of mild, moderate, or severe Alzheimer's disease. Rivastigmine is indicated for mild, moderate, or severe dementia associated with Alzheimer's disease or mild to moderately severe dementia associated with Parkinson's disease. Donepezil is used to treat mild to moderate Alzheimer's type dementia. All three drugs can cause side effects like nausea, diarrhea, insomnia, headaches and others.