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The National Institute on Aging's (NIA's) Alzheimer's Disease
Cooperative Study tested the effectiveness of a-tocopherol (also
known as vitamin E) and selegiline (also known as Eldepryl) in
slowing the progression of Alzheimer's disease. Researchers
were interested in these drugs because both are anti-oxidants--substances
that counteract oxidative damage. The progressive
loss of brain cells that occurs in Alzheimer's disease may
be related to oxidative damage. Besides acting as an anti-oxidant,
selegiline also increases the supply of dopamine and
catecholamines, important brain chemicals whose levels are
reduced in Alzheimer's disease.
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Taking selegiline, vitamin E, or a combination of the two drugs
delayed by about 7 months the time it took for patients to reach
one of four milestones: death, institutionalization (moving to a
nursing home), loss of the ability to perform activities of daily
living, or progression to severe dementia. In one commonly used
measure of everyday activities, patients in the three treatment
groups showed 25 percent less deterioration in activities such
as eating and dressing.
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The researchers believe it is now reasonable for doctors to
consider the use of either selegiline or vitamin E in patients
with moderately severe Alzheimer's disease. Today, no other
treatments have shown a similar ability to delay important
milestones in Alzheimer's disease.
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In this study, the selegiline and vitamin E were tolerated well
with few side effects. However, with both treatments, there are
potential problems as reported in other research. Selegiline,
which has been studied very carefully over a long period of time,
should not be taken with certain other drugs, specifically anti-depressants
or narcotics. Reported side effects of selegiline
include fainting, nausea, dizziness, confusion, vivid dreams,
and sometimes, low blood pressure.
Vitamin E is less well-studied, especially at high doses. As a
result, neither the long-term effects nor the potential hazards
of such high doses are known. Vitamin E may be associated with
increased bleeding in certain people, and some studies have
suggested that it should not be used with anti-coagulant
medications.
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The researchers tested a combination of selegiline and vitamin E
because these drugs seemed to work in different ways in animal
and cellular models of AD. These laboratory data strongly
suggested that they would have an additive effect. However,
in this study, people taking the two drugs did no better than
those taking either selegiline or vitamin E alone.
These findings may indicate that selegiline and vitamin E both
affect Alzheimer's disease in similar ways and, thus, there is no
advantage to taking both of them. The results show how important
it is to do well-controlled studies in people to determine the
effects of drugs and, in particular, combinations of drugs.
While laboratory studies may give us an idea of what will work,
only controlled studies in humans can tell us if these ideas are
correct.
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Should people in earlier or later stages of the disease
also consider therapy with vitamin E or selegiline? What about taking them
for prevention?
This study only addressed patients with moderately severe
disease. We do not know whether people in other stages of
Alzheimer's disease would benefit from these drugs. The only
drugs approved by the Food and Drug Administration (FDA) as safe
and effective in treating some symptoms of Alzheimer's disease
are tacrine (brand name Cognex) and donepezil (brand name
Aricept).
There is no evidence that any drug, including vitamin E and
selegiline, prevents Alzheimer's disease.
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Vitamin E, though relatively safe, may pose problems for some
people. It may be associated with increased risk of bleeding
in some people, especially those with bleeding problems. In
addition, the study used much higher doses of vitamin E than are
typically found in vitamin supplements. High doses of vitamin E
and its interaction with other drugs have not been well studied.
It is very important to check with a doctor before starting any
drug or supplement treatment.
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Selegiline is a prescription drug approved by the FDA to treat
Parkinson's disease. It is not approved for Alzheimer's disease
in the United States. The decision to take any drug must include weighing
benefits and risks. If a doctor concludes that a patient's
condition is similar to that of the patients in this study and
that the risks of selegiline are not serious for that patient,
the doctor may choose to prescribe it. Selegiline must be taken
under a doctor's supervision, in part because of its potential
side effects as discussed above.
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This study was not designed to show whether vitamin E and
selegiline are better than tacrine and donepezil, which both
work by increasing the supply of a brain chemical called acetylcholine.
The research shows that the two kinds of drugs affect
different symptoms. In this study, vitamin E and selegiline
reduced problems with everyday activities such as bathing and
dressing, delayed institutionalization, and slowed the advance
to severe dementia over a 2-year period. However, they did not
improve memory or cognition, which is seen with tacrine and
donepezil. In addition, patients in this study had a more
advanced stage of Alzheimer's disease than most patients who
have benefited from tacrine and donepezil.
There is no evidence that anti-oxidants, such as vitamin E and
selegiline, have additive effects when combined with drugs that
work on acetylcholine. While it may seem that the combination
should not be harmful, no one knows. Only carefully controlled
studies in patients can answer that question.
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The study showed that 2 years of treatment had a measurable
effect. We do not know if the effect would be the same if people
stopped treatment or if they continued treatment for a longer or
shorter period of time. Researchers did not study what would
happen if someone stopped treatment. However, there have been no
reports of serious adverse effects from stopping the treatment.
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Any improvements may not be apparent. These drugs have only been
shown to delay the effects of disease. The patient will not be
getting better, but he or she will be able to maintain basic
functional activities longer.
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We do not know. Other studies have examined these drugs in
patients with Huntington's disease and Parkinson's disease, but
have found no improvements in cognition or effect on dementia in
these diseases.
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Research is needed to test the effectiveness of anti-oxidants in
both the earlier and later stages of Alzheimer's disease. More
work needs to be done to determine if these drugs can provide an
added benefit when used in combination with other medications to
treat dementia.
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What if I have other questions about the study or about
Alzheimer's disease?
For further information about Alzheimer's disease, please
call the Alzheimer's Disease Education and Referral (ADEAR) Center toll-free
at 1-800-438-4380 or or e-mail us at
adear@alzheimers.org.
Released in April 1997
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