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Alzheimer's Drugs Offer Modest Improvements, Equal
Effectiveness
Aricept, Razadyne, Exelon studies reviewed
By Becky Ham, Science Writer
Health Behavior News Service
Feb. 5, 2006 - The Alzheimer’s drugs Aricept,
Razadyne and Exelon can lead to small improvements in mental functioning
and the ability to carry out everyday activities in people with mild to
moderate forms of the disease, according to a new review of recent
studies.
Although the three drugs work in slightly different
ways, the few head-to-head studies of the drugs — all funded by
pharmaceutical companies — found them equally effective, according to
review author Jacqueline Birks of the University of Oxford.
The review appears in the January issue of The
Cochrane Library, a publication of The Cochrane Collaboration, an
international organization that evaluates medical research. Systematic
reviews draw evidence-based conclusions about medical practice after
considering both the content and quality of existing medical trials on a
topic.
Birks’ review included 13 high-quality studies
involving 7,298 patients from North America, Europe and Australia. The
studies compared the three drugs against placebo treatment, with 2,228
patients in the Aricept studies, 2,267 in the Razadyne studies and 2,803
in the Exelon studies.
The effects of the drugs were not very large when
measured across the 13 studies, Birks found. In one measure of how well
the drugs worked, for instance, patients across the studies improved by
an average of less than three points on a 70-point scale that tracks
mental functioning.
“There is nothing to suggest the effects are less
for patients with severe dementia, although there is very little
evidence for other than mild to moderate dementia,” she said.
Side effects caused about 29 percent of the
patients taking the drugs to leave the studies, compared with 18 percent
dropout among the patients taking a placebo. The most common side
effects were nausea, vomiting and diarrhea.
Birks found fewer reported side effects among
patients taking Aricept, but she suggests that this may have to do with
the way Aricept and the other two drugs are prescribed.
Razadyne and Exelon have a “ramp-up” period in
which patients take increasingly higher doses to get to a therapeutic
level of treatment. Birks says the two drugs may be as tolerable as
Aricept if they are gradually introduced over a course of three months.
In a second review focusing on Aricept only, Birks
and researcher Richard Harvey found that a 5 milligram a day dose of the
drug was only slightly less effective than a 10 milligram a day dose,
with fewer side effects.
In another, newly updated Cochrane review, Dr.
Clement Loy of Garvan Institute of Medical Research in Australia and
colleagues concluded that Razadyne can improve or maintain mental
functioning at a 16 milligram a day dose.
The three drugs are from a class of medicines
called cholinesterase inhibitors. They boost chemical signaling in a
group of brain neurons that are typically destroyed during the course of
Alzheimer’s disease.
Birks said there is no way to know ahead of time
whether the inhibitors will work on a particular Alzheimer’s patient,
but some researchers recommend starting the treatment as soon as
possible after a diagnosis.
George Grossberg, M.D., a specialist in Alzheimer’s
treatment at the Saint Louis University School of Medicine, said there
is ample evidence that “the earlier one starts the better” for slowing
the progression of the disease.
“In fact, patients who come to drugs later, even as
little as six months later, never catch up with those who were on drug
from the outset,” of their diagnosis, Grossberg said.
Although the review of Aricept showed that the drug
can be effective even 52 weeks after the start of treatment, Birks says
more long term studies of the medicines are needed.
“As Alzheimer’s disease generally progresses slowly
and clinical course of five to 10 years is not unusual, clinical trials
of six or 12 month duration are of limited use,” she noted.
Longer trials could also provide more information
on whether these drugs are cost-effective treatments. For the moment,
there is only limited data on how these drugs affect the overall cost of
care for Alzheimer’s patients, Birks found.
The review of Aricept was supported by the British
National Health Service, University of Melbourne and Barwon Health,
Australia.
The Cochrane Collaboration is an international
nonprofit, independent organization that produces and disseminates
systematic reviews of health care interventions and promotes the search
for evidence in the form of clinical trials and other studies of
interventions. Visit http://www.cochrane.org for more information.
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