ExplanationMemantine is the only listed drug that is not an acetylcholinesterase inhibitor. Memantine is a low-to-moderate affinity noncompetitive NMDA receptor antagonist and is approved for moderate–severe dementia in Alzheimer’s disease (AD). The other listed drugs in question 28 are acetylcholinesterase inhibitors. Tacrine is no longer available in United States due to hepatotoxicity. Patients with AD have reduced cerebral production of choline acetyl transferase, which leads to a decrease in acetylcholine synthesis and impaired cortical cholinergic function. Donepezil, rivastigmine, galantamine, and memantine are all medications used in the treatment of dementia, most commonly AD. Donepezil is a pure acetylcholinesterase inhibitor. Rivastigmine is a combined acetylcholinesterase and butyrylcholinesterase antagonist, both of 993 which result in limiting the breakdown of acetylcholine. Galantamine is a combined acetylcholinesterase inhibitor and allosteric nicotinic modulator. Memantine is an NMDA receptor antagonist that inhibits glutamate stimulation and thus theoretically limits overactivation and toxicity to remaining cholinergic neurons. Memantine also has some antagonistic action at the 5HT3 serotonin receptor.
