is the only acetylcholinesterase
inhibitor approved for use in all stages
of the disease. The N-methyl-t-aspartate
receptor antagonist memantine (Namenda)
is approved for treating moderate to severe
disease, and is thought to prevent excitatory
amino acid neurotoxicity without interfering
with the physiologic actions of glutamate, a
neurotransmitter necessary for learning and
memory.l3