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news.According to the findings of a new study, a careful desensitization protocol can help patients overcome allergic reactions to clopidogrel, an anti-clotting medication critical to preventing new blockages inside coronary stents.
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In the study, eight patients with clopidogrel hypersensitivity were treated with the desensitization protocol, which was developed by University of Iowa allergist Dr Mary Beth Fasano. 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 75mg. Altogether, they received nine clopidogrel doses totaling 150mg.
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 75mg dose of clopidogrel at home without experiencing delayed allergic reactions.
Dr Nicholas Walker, the study’s lead author and a cardiology fellow at the University of Iowa, 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.
It is believed that perhaps two out of every hundred patients treated with clopidogrel (marketed as Plavix by Bristol-Myers Squibb and Sanofi-Aventis) 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.
In addition, 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.