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Other cardiovascular
medications: Aspirin
(This article was first printed in the Special
Health Report from Harvard Medical School "The
Healthy Heart: Preventing, Detecting, and Treating
Coronary Artery Disease". For more
information or to order, please go to www.health.harvard.edu/HH.)
Aspirin is an old standby, yet it continues
to surprise. This common, inexpensive drug helps
protect survivors of heart attack and stroke
from subsequent heart attacks and death, and
even helps reduce the number of deaths that occur
within the first hours following a heart attack.
Although aspirin is best known as an antiplatelet
drug, it may also subdue the inflammation that
is central to coronary artery disease.
Randomized trials have provided clear evidence
of aspirin’s value in both preventing heart
attacks in men and treating coronary artery disease
in both sexes. Over all, dozens of studies, involving
tens of thousands of people, have shown that
low-dose aspirin reduces the risk for heart disease
and stroke by about 25%. A standard dose of aspirin
to prevent heart attack is 81 mg per day, about
what you’d find in a baby aspirin.
Guidelines from nearly every major medical group
urge people with heart disease or at high risk
for it to take aspirin. Although a major study
reported in 2005 concluded that the advice is
not as clear-cut for how to prevent first heart
attacks in women (see “Advice for women,” below),
the prevailing consensus remains that in general,
unless you are allergic to aspirin or it causes
you problems, you should take it if you
- have had a heart attack
- have had an ischemic (clot-caused) stroke
or a mini-stroke (transient ischemic attack)
- have angina (chest pain)
- have had a coronary artery bypass or angioplasty
- have diabetes
- are at high risk for heart disease.
Despite aspirin’s benefits, it also has
some drawbacks. The evidence that its benefits
exceed its risks is much stronger in men than
in women, at least in terms of primary prevention
(avoiding a first cardiovascular event). It can
increase the risk for stroke and significant
gastrointestinal bleeding. Even people who take
aspirin occasionally with no problems could experience
bleeding complications with regular use over
prolonged periods. In particular, it may not
be a good choice for people with uncontrolled
hypertension (a major cause of hemorrhage into
the brain). In such people, aspirin could more
likely cause dangerous bleeding than prevent
a heart attack. In addition, aspirin occasionally
irritates the stomach lining without causing
bleeding. However, these side effects can be
reduced with the use of coated aspirin, which
minimizes stomach irritation.
Advice for women. The first
large-scale randomized study to specifically
examine aspirin’s effectiveness in preventing
first heart attacks in healthy women, reported
in the New England Journal of Medicine in
2005, showed that the risk/benefit analysis for
aspirin is not as straightforward in women as
it is in men. The study involved almost 40,000
healthy women ages 45 and older, who took 100
mg of aspirin or a placebo every other day. To
their surprise, the researchers found that aspirin
did not affect the risk for a first heart attack
one way or the other in the group as a whole,
although it did reduce the risk for stroke by
17%. Yet when the researchers did subgroup analyses,
they discovered that aspirin significantly reduced
the risk for first heart attack, stroke, and
other cardiovascular events in women who were
65 and older. This benefit has to be weighed,
however, against an increased risk for gastrointestinal
bleeding.
So what do you do? If you’re a woman who
has already had a heart attack, stroke, or some
other cardiovascular event, the advice remains
the same: Take aspirin to reduce the risk for
a second event. (A large study that looked at
such secondary prevention concluded that aspirin
benefits both men and women.) But if you’re
considering taking aspirin to prevent a first
event, the advice is less clear-cut. Talk with
your physician to determine whether — in
your case — the benefits outweigh the risks.
Aspirin resistance. Some people
are resistant to aspirin’s anticlotting
effects. So far the research indicates that aspirin
fails to affect platelets’ tendency to
clump, or does so only partially, in 5%–40%
of people who take it. These people therefore
don’t have the same reduction in heart
attack and stroke risk that other people gain
from aspirin use.
There are probably several reasons why aspirin
resistance occurs. The body’s response
to aspirin may change over time. Some people
have trouble absorbing aspirin from the digestive
tract. Smoking blunts the effect of aspirin on
platelets, as do being overweight and having
high cholesterol or high blood pressure. A variety
of genes influence how the body responds to aspirin.
Finally, a few studies have indicated that a
common nonsteroidal anti-inflammatory drug (NSAID),
ibuprofen, may block aspirin’s protective
effects. The occasional dose of ibuprofen isn’t
likely to do this, but daily use could.
Although two laboratory tests are available
to measure how well aspirin may be working for
you, the idea of aspirin resistance is so new
that many doctors either aren’t aware of
it or are waiting for more evidence that it’s
real before ordering these tests. So what do
you do in the meantime? First, talk with your
doctor about being tested for aspirin responsiveness.
Second, if you need to take an NSAID for arthritis
or some other condition, pick one that doesn’t
interfere with aspirin, such as naproxen (Aleve,
Naprosyn) or diclofenac (Cataflam, Voltaren).
Third, don’t stop taking aspirin — regardless
of whether you can get tested or what the results
are. Aspirin probably works in several ways to
prevent heart attacks. If do you find you are
aspirin resistant, talk with your doctor about
other antiplatelet medications.
Several other options are available to inhibit
platelets, but these tend to be more expensive
than aspirin and are not as well studied.
(This article was first printed in the Special
Health Report from Harvard Medical School "The
Healthy Heart: Preventing, Detecting, and Treating
Coronary Artery Disease". For more
information or to order, please go to www.health.harvard.edu/HH.)
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