Back to Neurology Articles
Friday, 5 November 2004 05:30 PM
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New drugs may help in blocking the accumulation of the brain-clogging beta-amyloid
protein thought to cause Alzheimer's disease.
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This month witnessed the discovery of two drugs that may help in
treating Alzheimer's disease. On the other hand, it has been announced
that a large-scale study will be launched next April with the aim of
better understanding this disease.
Alzheimer's disease (AD)
affects approximately 4.5 million Americans. It is considered the most
common cause of dementia in western countries. Approximately 10% of all
persons over the age of 70 have significant memory loss; in more than
half, the cause is
AD.
AD is
a progressive dementia
(that is the
dementia keeps getting worse).
The most important risk factors for AD are old age and a positive
family history. The frequency of AD increases with each decade of adult
life to reach 20 to 40% of the population over the age of 85. A positive
family history of dementia suggests a genetic cause of AD.
Mechanism
AD is characterized in the brain by abnormal clumps (amyloid plaques)
and tangled bundles of fibers (neurofibrillary tangles) composed of
misplaced proteins. Three genes have been discovered that cause early
onset (familial) AD. Other genetic mutations that cause excessive
accumulation of amyloid protein are associated with age-related
(sporadic) AD.
The management of Alzheimer's disease is difficult and frustrating, because
there is no specific treatment and no way to slow the progression of the
disease. The primary focus is on long-term amelioration
of associated behavioral and neurologic problems. Currently there are
five FDA-approved drugs that may benefit some people in the early or
middle stages of the disease. Tacrine (Cognex) may alleviate some
cognitive symptoms. Donepezil (Aricept), rivastigmine (Exelon), and
galantamine (Reminyl) may keep some symptoms from becoming worse for a
limited time.
"In recent studies, the benefit of these medications were
shown to be more effective in the early and middle stages of Alzheimer's
and less effective in the last stage", comments Carolyn Merritt, LPN of
The Doctors Lounge. "The studies seemed to show it delayed the onset of
the third and final stage".
The fifth drug, memantine (Namenda), was recently approved
for use in the United States.
US launches major study
In April 2005, researchers will begin recruiting about 800 Americans,
ranging from 55 to 90 years old, in an effort to gain a better
understanding of the early stages of the disease. This will be part of a
major government study to track early Alzheimer's disease.
Researchers will use MRIs of the brain and other tests to track
people who have either early-stage disease or a milder type of memory
loss known as "mild cognitive impairment." Over the course of five
years, they will compare the biological changes that occur within those
patients' brains to the aging that takes place in the brains of healthy
seniors.
The goal is to find early warning signs that can identify
people at highest risk, and markers to help test the effectiveness of
new therapies. The study, which will cost approximately $60 million
(mostly funded by the government), was unveiled Wednesday by the
National Institute on Aging.
New hope
In the lab, scientists said they had designed a drug that
appears to block the accumulation of the brain-clogging beta-amyloid
protein. The study was published in last week's issue of the journal
Science. This new drug, although promising, is still in its pre-clinical
testing stage. Scientists will now proceed to test it in animal models
with versions of Alzheimer's disease.
Earlier this week, a team at the National Institute of Environmental
Health Sciences and the University of Wisconsin said they found a
naturally occurring brain protein that stops the progression of
Alzheimer's disease in human brain tissue. The protein, called transthyretin, appears to protect brain cells by intercepting beta-amyloid
protein before it can damage brain tissue. Drugs that boost
transthyretin levels may help treat or even prevent the disease.
| Edited
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Carolyn Merritt (Licensed Practical Nurse).
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Reviewed
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Theresa Jones (Registered Nurse).
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