May 11, 2006 --
A careful desensitization protocol can help patients overcome allergic
reactions to anti-clotting
medication critical to preventing new blockages inside coronary
stents, according to a study being presented at the Society for
Cardiovascular Angiography and Interventions (SCAI) 29th Annual
Scientific Sessions in Chicago, May 10–13. (Time of Presentation:
Thursday, May 11, 10:39 a.m. Central Time)
“Allergic reactions can be quite frightening to patients and physicians,
and can lead to discontinuation of the medication,” said
the study’s lead author, Nicholas E. Walker, MD, a cardiology
fellow at the University of Iowa, Iowa City. “We showed we
could successfully and safely desensitize patients who had just
recently had a drug-eluting stent placed. That’s a critical
population to manage.”
Perhaps two out of every hundred patients treated with the anti-clotting
medication clopidogrel develop an allergic reaction marked by rash,
itching, hives, or swelling of the tongue and airway. A small number
of patients even develop an anaphylactic reaction and go into shock.
Physicians generally discontinue a medication that provokes an
allergic reaction and prescribe an alternative. However, in the
case of clopidogrel, substitute medications are either just as
likely to provoke allergy symptoms or markedly less effective.
Stopping the medication may be riskier than continuing it: Patients
who do not take clopidogrel after stenting—particularly after
receiving a drug-eluting stent—face approximately three times
the risk of a blood clot blocking the stent and causing a heart
attack.
“
With widespread use of drug-eluting stents, it’s going to
be more common to see allergic reactions to clopidogrel, and more
critical that we find a way to keep patients on the medication,” said
Phillip A. Horwitz, MD, a professor of medicine and an interventional
cardiologist at the University of Iowa Hospitals and Clinics.
Eight patients with clopidogrel hypersensitivity were treated with
the desensitization protocol, which was developed by University
of Iowa allergist Mary Beth Fasano, MD. While being monitored in
the cardiac intensive care unit, patients were first given a dose
of clopidogrel so small it had to be mixed into a drinkable solution.
Every 15 minutes over the next several hours they received an additional,
higher dose of the drug, until they were able to tolerate a target
dose of 75 mg. Altogether, they received nine clopidogrel doses
totaling 150 mg.
Patients who developed allergy symptoms during the desensitization
process were treated with antihistamines and other anti-allergy
medications. All patients were able to complete desensitization
and safely take a daily 75-mg dose of clopidogrel at home without
experiencing delayed allergic reactions.
Dr. Walker noted that patients who had the most severe form of
allergic reaction to clopidogrel—anaphylactic shock—were
excluded from the study; therefore, the safety and effectiveness
of the desensitization protocol has not been established in such
patients.
Headquartered in Bethesda, Md., the Society for Cardiovascular
Angiography and Interventions is a 3,400-member professional organization
representing invasive and interventional cardiologists. SCAI’s
mission is to promote excellence in invasive and interventional
cardiovascular medicine through physician education and representation,
and advancement of quality standards to enhance patient care. SCAI
was organized in 1976 under the guidance of Drs. F. Mason Sones
and Melvin P. Judkins. The first SCAI Annual Scientific Sessions
were held in Chicago in 1978.
source: The Society for Cardiovascular
Angiography and Interventions (SCAI)
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