is a neurotransmitter,
a chemical substance which neurons in the brain use to communicate
with one another. Cholinesterase is an enzyme
which normally cleans up unused acetylcholine, by breaking
it down into its components acetate and choline. These components
can then be recycled for later use.
Cholinesterase inhibitors are drugs that
prevent (or inhibit) cholinesterase from cleaning up unused
acetylcholine; the result is that individual acetylcholine
molecules survive longer.
Neurons which produce acetylcholine are
among the first to be damaged in Alzheimer's
disease, with the result that levels of acetylcholine
fall in the brain. Cholinesterase inhibitors may be useful
in these patients by allowing what acetylcholine there is
to survive longer and be more effective.
Four cholinesterase inhibitors, tacrine
(brand name Cognex), donepezil
(brand name Aricept), rivastigmine
(brand name Exelon) and galantamine
(brand name Reminyl) have been approved by the FDA for use
in treating Alzheimer's disease. All produce some limited
improvement in the cognitive symptoms associated with Alzheimer's
disease, though they do not slow or halt the progression of
the disease. The beneficial effects are typically modest and
temporary. Tacrine can also produce severe side-effects including
liver damage. Several other cholinesterase inhibitors, including
physostigmine, rivastigmine and metrifonate, are currently
under investigation by the FDA to see if they can produce
reliable improvements in AD symptoms without undue side effects.
Krall WJ, Sramek JJ, Cutler NR (1999) Cholinesterase
inhibitors: a therapeutic strategy for Alzheimer disease.
Annals of Pharmacotherapy, 33(4):441-50. Also check the NIH
for the most current details about these and other drugs currently
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain