Drug-Eluting Stents
May
Cause Allergic Reactions
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December 29, 2005 -- A new
study appearing in next week's Journal of the American College
of Cardiology reports on a phenomenon
that is not news to us here at Angioplasty.Org: allergic reactions
to drug-eluting stents. Our Forum
Topic has received almost 90 postings from patients on the subject,
most in the past two years since the introduction of drug-eluting
stents. The Northwestern study used a number of sources for the adverse
reactions, among them the FDA MAUDE database. The study found definite
allergic reactions to the stents themselves -- possibly to the polymer
coatings on the stents. Symptoms included rash, difficulty breathing,
hives, itching and fevers. The team reviewed 5,783 reports and identified
17 as probable or definite allergic reactions to the stents, 4 of
which resulted in death. This is a very small percentage: only 0.3%
of the adverse reports and only 17 out of a couple million stents,
but it is significant (although it is our opinion that these adverse
reactions are under-represented in the official data sources).
The sudden occurrence of an allergic reaction after
stenting can have multiple causes. A common one is allergic reactions
to the drug regimens required, such as Plavix (clopidogrel), aspirin
or some of the many other medications that heart patients need to
take which can cause rashes and other symptoms. Some patients are
allergic to the contrast solution or dye that is used during the
angioplasty procedure. Some have shown reactions to the bovine collagen
used in some vascular closure devices which seal the femoral artery
after the procedure. A few patients have metal allergies to nickel
or stainless steel, something seen rarely even in the era of bare
metal stents, but still significant for the patient (stent companies
in fact caution physicians NOT to implant a stent in patients with
known metal allergies -- good idea!). With the addition of a polymer
coating and a drug being eluted into the bloodstream, two more variables
have been introduced.
Dr. Charles Bennett, MD,
PhD of Northwestern states, "Physicians
should be cognizant that allergic reactions to the polymers in drug
eluting stents can occur and all such events should be reported to
the FDA. Six months after the approval of the first drug-eluting
stent, the FDA issued a letter to physicians identifying 50 hypersensitivity
cases associated with drug-eluting coronary artery stents, but retracted
an assertion of causality a month later. That retraction may have
been premature." We agree with Dr. Bennett, given the number
of adverse reaction reports we've gotten.
We also agree with another
of the study's authors, Dr. Charles J. Davidson, who heads the
cath lab at the Bluhm Cardiovascular
Institute of Northwestern Memorial Hospital, when he says, "Drug-eluting
stents are a life-saving advance used by hundreds of thousands of
people that have greatly reduced the risk of restenosis. We are in
no way recommending they be used less, but we do think that health
professionals should be vigilant in watching for this problem." The
authors also suggest that perhaps some type of skin test be developed
that can be used prior to stenting to screen out patients who may
have allergies. This is a request that's been made by several of
our readers who are patients -- we think it's an important one and
should include a test for drug allergies as well -- if a patient
is allergic to the stent, the polymer, clopidogrel or other necessary
post-procedure medications, these facts should be known before stent
placement.
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