An 84-year-old man with Alzheimer's disease has progressed from mild to moderate; which additional treatment is most likely to be added to his current therapy?

• A. Memantine
• B. Rivastigmine
• C. Galantamine
• D. Donepezil

Answer: (A)

As Alzheimer's disease advances from mild to moderate while a cholinesterase inhibitor is already being used, adding a medication with a different mechanism is often beneficial. Memantine is an NMDA receptor antagonist that reduces glutamatergic excitotoxicity, a process that becomes more relevant in moderate-to-severe disease. It is approved for moderate-to-severe AD and is commonly started in addition to ongoing cholinesterase inhibitor therapy to provide extra symptomatic benefit without duplicating the cholinergic mechanism. The other options are cholinesterase inhibitors themselves, which are usually used earlier in disease; adding another cholinesterase inhibitor offers less additional benefit and can increase cholinergic side effects, whereas memantine adds a distinct, complementary approach.