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| |  Desensitization Can Eliminate Clopidogrel Allergy: Presented at SCAI By Crystal Phend CHICAGO, I.L. -- May 12, 2006 -- A desensitization protocol appears to overcome allergies to the anti-clotting medication clopidogrel, according to research presented here at the Society for Cardiac Angiography and Interventions 29th annual Scientific Sessions (SCAI). "Management of these patients can be challenging, especially when the hypersensitivity reaction presents after intracoronary drug-eluting stent implantation," said lead author Nicholas E. Walker, MD, cardiology fellow, University of Iowa, Iowa City, Iowa, in a presentation here on May 11th. Allergic reactions to clopidogrel, which can include anaphylaxis, are rare but have been estimated to occur in 1% to 2% of patients who are treated with the drug. Although drug allergy is typically managed by prescribing an alternate medication, clopidogrel alternatives are either just as likely to provoke allergy symptoms or markedly less effective. Desensitization -- the process of inducing tolerance -- was tested in 8 patients in the study. Half had prior experience with clopidogrel after a prior stent placement and thus were already known to be allergic to clopidogrel; half developed the allergy after stent placement and had no previous exposure to the drug. Patients with anaphylaxis were excluded from the study. The desensitization protocol used escalating doses of clopidogrel starting at 0.2 mg and moving up to a dose of 75 mg in 15-minute intervals. Patients were then monitored overnight. Follow up by telephone was continued for 3 months and every 3 months after that. The most common allergic reactions were maculopapular rash, pruritis and urticaria. Desensitization was successful in all patients and there were no serious hypersensitivity reactions. There were 2 minor hypersensitivity reactions during desensitization -- 1 with mild pruritis and 1 with pruritis and urticaria. After a mean follow up time of 7.5 months, all patients remain on clopidogrel with no further allergy reactions. Dr. Walker said the desensitization protocol should not be used in patients with Stevens-Johnson syndrome or other exfoliative dermatitis reactions. He also emphasized that maintaining the desensitization requires that the clopidogrel therapy not be interrupted or stopped. Although "the precise mechanism by which desensitization works is unknown," he said that it does work based on his group's results.
[Presentation title: Clopidogrel Desensitization Protocol for the Treatment of Thienopyridine Hypersensitivity: Initial Clinical Experience. Abstract O-3]
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