Parkinson's drug may hasten Alzheimer's
Common treatment might
exacerbate brain build-ups.
28 July 2003
HELEN PEARSON
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5-10% of Parkinson's
patients receive
antimuscarinic
drugs. |
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© GettyImages |
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Drugs given to Parkinson's patients and the elderly
may hasten the onset of Alzheimer's disease, a
preliminary study hints.
Antimuscarinic drugs are prescribed to an estimated
5-10% of Parkinson's patients to help control tremors,
bladder problems and depression. They block some of the
actions of a brain chemical called acetylcholine.
Parkinson's patients who had taken the medicines for
more than two years had roughly twice the usual level of
protein usual level of protein clumps and tangles
compared to those not on drugs, found Elaine Perry of
Newcastle General Hospital, UK. Clumps and tangles are
characteristic of Alzheimer's patients. Perry's team
examined 120 records from a British brain bank, obtained
from patients over 70 years of age1.
Doctors should not jump to switch therapies, the team
says. None of the patients examined had actually shown
symptoms of Alzheimer's. And antimuscarinic drugs are
used less and less to treat Parkinson's now, because of
short-term side-effects such as confusion.
But there is cause for concern, believes Allan Levey,
who studies nervous-system disease at Emory School of
Medicine in Atlanta, Georgia. Millions of people take
drugs such as tricyclic antidepressants,
antihypertensives and antihistamines that block
acetylcholine indirectly, he points out, even though
these medicines target other molecules.
"It's hard to find elderly people who aren't on
them," Levey says. New studies should monitor whether
these patients are at greater risk of Alzheimer's, he
suggests.
Up side
More optimistically, if drugs that block
acetylcholine encourage Alzheimer's, then others that
fire up the acetylcholine system might stop or slow the
brain disease. 'That's the more exciting aspect," Perry
says.
Already acetylcholine boosters, such as
rivastigamine, are frequently used to ease the symptoms
of Alzheimer's. But they were not thought to deal with
the plaques of twisted beta-amyloid protein that
characterize the disease and are implicated in dementia.
Animal studies suggest that acetylcholine stimulants
stall plaque growth; human trials are under way to
explore whether the drugs protect people from
Alzheimer's. |
