All of the following are prescription medications currently approved by the FDA for Alzheimer's treatment except

A. Exelon (rivastigmine) is an FDA-approved medication for Alzheimer's disease. It is a cholinesterase inhibitor that works by increasing levels of acetylcholine, a neurotransmitter important for memory and learning . B. Risperdal (risperidone) is not approved by the FDA for the treatment of Alzheimer's disease. It is an atypical antipsychotic medication primarily used to treat schizophrenia and bipolar disorder. While it may be prescribed off-label for managing certain behavioral symptoms in Alzheimer's patients, its use in this context carries significant risks, including increased mortality in elderly patients with dementia-related psychosis . C. Namenda (memantine) is an FDA-approved medication for moderate to severe Alzheimer's disease. It is an NMDA receptor antagonist that helps regulate glutamate activity, which is involved in learning and memory . D. Aricept (donepezil) is an FDA-approved medication for all stages of Alzheimer's disease. It is a cholinesterase inhibitor that increases levels of acetylcholine in the brain .