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Drug-Eluting Stents May Cause Allergic Reactions

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Drug Eluting Stents May Cause Allergic Reactions
Northwestern Memorial Hospital

Hypersensitivity Cases Associated With Drug-Eluting Coronary Stents
Journal of the American College of Cardiology

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.