Source:www.alz.org
While there is no cure for Alzheimer’s disease, there are five prescription drugs approved by
the U.S. Food and Drug Administration (FDA) to treat its symptoms.
Donepezil, galantamine, rivastigmine and tacrine are called cholinesterase inhibitors.
Memanatine is classified as an uncompetitive low-to-moderate affinity N-methyl-D-aspartate
(NMDA) receptor antagonist. Both types of drugs help manage symptoms, but work in
different ways.
Understanding available treatment options can help you and your loved one cope with
symptoms and improve quality of life. Here is more detailed information about the FDAapproved drugs
Cholinesterase inhibitors
What are cholinesterase inhibitors?
Cholinesterase inhibitors are prescribed to treat symptoms related to memory, thinking,
language, judgment and other thought processes. Three different cholinesterase inhibitors are
commonly prescribed:
• Donepezil (marketed under the brand name Aricept), which is approved to treat all
stages of Alzheimer’s disease
• Galantamine (marketed under the brand name Razadyne), also approved for mild to
moderate stages.
• Rivastigmine (marketed under the brand name Exelon), approved for mild to
moderate Alzheimer’s
Tacrine (Cognex), the first cholinesterase inhibitor, was approved in 1993 but is rarely
prescribed today because of associated side effects, including possible liver damage.
How do cholinesterase inhibitors work?
Cholinesterase inhibitors work by increasing levels of acetylcholine, a chemical messenger
involved in memory, judgment and other thought processes. Here’s how: Certain brain cells
release acetylcholine, which helps deliver messages to other cells. After a message reaches the
receiving cell, various other chemicals, including an enzyme called acetylcholinesterase, break
acetylcholine down so it can be recycled.
But Alzheimer’s disease damages or destroys cells that produce and use acetylcholine, thereby
reducing the amount available to carry messages. A cholinesterase inhibitor slows the
breakdown of acetylcholine by blocking the activity of acetylcholinesterase. By maintaining
acetylcholine levels, the drug may help compensate for the loss of functioning brain cells.
Cholinesterase inhibitors seem to offer other benefits, as well. For example, galantamine
appears to stimulate the release of acetylcholine and to strengthen the way certain messagereceiving nerve cells respond to it. Rivastigmine may block the activity of another enzyme
involved in breaking down acetylcholine.
1Cholinesterase inhibitors can’t reverse Alzheimer’s and won’t stop the underlying destruction
of nerve cells. Consequently, their ability to improve symptoms eventually declines as brain
cell damage progresses.
What are the benefits of cholinesterase inhibitors?
In clinical trials of all three cholinesterase inhibitors, people taking the medications performed
better on memory and thinking tests than those taking a placebo, or inactive substance. The
degree of benefit was small, however, and more than half of the recipients showed no
improvement at all.
In terms of overall effect, most experts believe cholinesterase inhibitors may delay or slow
worsening of symptoms for about six months to a year; although some people may benefit
more dramatically or for a longer time.
There is no evidence that combining the drugs would be more helpful than taking any one of
them. In fact, combining them would likely result in greater frequency of side effects.
There is some evidence that individuals with moderate to severe Alzheimer’s who are taking a
cholinesterase inhibitor might benefit by also taking memantine.
What are common side effects of cholinesterase inhibitors?
Cholinesterase inhibitors are generally well tolerated. If side effects occur, they commonly
include nausea, vomiting, loss of appetite and increased frequency of bowel movements. It is
strongly recommended that a physician who is experienced in using these medications
monitor patients who are taking them, and that the recommended guidelines be strictly
observed.
Memantine (Namenda)
What is memantine?
Memantine (Namenda) is prescribed to improve memory, attention, reason, language and the
ability to perform simple tasks. It was the first Alzheimer drug of the NMDA receptor
antagonist type approved in the United States. It's used to treat moderate to severe
Alzheimer’s. In 2005, the FDA declined to approve memantine for mild Alzheimer’s.
How does memantine work?
Memantine appears to work by regulating the activity of glutamate, a chemical involved in
information processing, storage and retrieval. Glutamate plays an essential role in learning and
memory by triggering NMDA receptors to let a controlled amount of calcium into a nerve
cell. The calcium helps creates the chemical environment required for information storage.
Excess glutamate, on the other hand, overstimulates NMDA receptors so that they allow too
much calcium into nerve cells. That leads to disruption and death of cells. Memantine may
protect cells against excess glutamate by partially blocking NMDA receptors.
What are the benefits of memantine?
One clinical study showed that people taking memantine showed a small but statistically
significant improvement in their mental function and ability to perform daily activities. But
2study participants with lowest cognitive functioning showed no improvement on either daily
activities or overall function.
Another study randomly assigned participants to receive either 10 mg of memantine twice a
day, or a placebo in addition to donepezil (Aricept), a cholinesterase inhibitor. Those receiving
memantine showed a statistically significant benefit in mental function and performing daily
activities, while participants taking donepezil plus placebo continued to decline.
What are common side effects of memantine?
Adverse side effects include headache, constipation, confusion and dizziness.
At-a-glance treatment chart
Generic Brand Approved For Side Effects
donepezil Aricept All stages Nausea, vomiting, loss of appetite
and increased frequency of bowel
movements.
galantamine Razadyne Mild to moderate Nausea, vomiting, loss of appetite
and increased frequency of bowel
movements.
memantine Namenda Moderate to severe Headache, constipation, confusion
and dizziness.
rivastigimine Exelon Mild to moderate Nausea, vomiting, loss of appetite
and increased frequency of bowel
movements.
tacrine Cognex Mild to moderate Possible liver damage, nausea, and
vomiting.
On the horizon
Scientists have made remarkable progress in understanding how Alzheimer’s affects the brain.
Their insights point toward promising new treatments to slow or stop the disease. Ultimately,
the path to effective therapies is through clinical studies.
If you or a loved one is interested in participating in a clinical study, please see the Clinical
Studies section on www.alz.org. There you can find information about how clinical trials
work and a list of current trials underway.
The Alzheimer’s Association is the leading voluntary health organization in Alzheimer care,
support and research.
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