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FDA Alert: Plavix
May Be Less Effective in Some Patients with Genetic Variation
Warning is of Special Importance to Stent Patients
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March
12, 2010 --
What some clinicians have known about
for some time is now official: the U.S.
Food and Drug Administration today added a boxed warning to the
drug Plavix (clopidogrel) stating that, in some patients with
a genetic variation
of the cytochrome CYP2C19, Plavix may not be metabolized properly
and therefore may not be effective for the indicated therapy.
For these patients, an increased dose of Plavix or an alternative
antiplatelet medication, such as prasugrel, may be indicated. |
This is of special importance to stent recipients
who depend on Plavix as a potent antiplatelet drug to keep blood
clots from forming inside their stent. Without the anti-clotting
protection of Plavix, platelets in the blood can gather together
inside the stent, forming
a thrombus (stent thrombosis) and blocking blood flow to the
heart, resulting in a possible heart attack or even death.
Dr. Eric J. Topol,
Director of the Scripps Translational Science Institute (STSI)
in La Jolla,
California, has been one of the leaders in bringing
this issue to the forefront. In his recent
interview with Angioplasty.Org,
Dr. Topol discussed the protocol at Scripps: every stent patient
is tested for CYP2C19, as well as platelet reactivity, so that
the proper post-stenting medications can be prescribed for peak
effectiveness. He stated:
"This is not what I consider
research, this is clinical care! This is being able to make
the call of when it's ready for prime time -- that is taking
care
of patients. We have the genotype
data for all the patients and we will assess their outcomes,
but that's
not why we're doing this. This is because we feel, and I
strongly feel, that knowing this information today we can't
wait. This
is a vital thing to have in the care of patients. With all
that we know today, the evidence is compelling."
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Eric J. Topol,
MD
Scripps Translational
Science Institute
La Jolla, CA
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The FDA statement emphasizes that "patients should not
stop taking Plavix unless told to do so by their health care professional.
They should talk with their health care professional if they have
any concerns about Plavix." The issue is not that Plavix
causes a problem, but that in a percentage of patients, it may not
be effective. Sanofi-aventis and Bristol-Myers Squibb, the manufacturers
of Plavix, state that approximately 3% of the patient population
may be affected -- broken down by ethnicity, their estimate of poor
metabolizers is approximately 2% of whites, 4% of blacks, and 14%
of Chinese. However, Dr. Topol told Angioplasty.Org that studies have
shown lack of response of clopidogrel for antiplatelet effect occurs
in at least 30% of individuals.
The take-away message for patients and professionals
alike is that for stent patients on dual antiplatelet therapy, it
is a good idea to measure platelet reactivity and to test for the
CYP2C19 variation -- some hospitals already do this.
The full press release from the FDA is available
on
their website.
Reported by Burt Cohen, March 12, 2010
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