Clopidogrel is a widely used antiplatelet agent, particularly after coronary stent implantation. About 1% of patients have allergic or hematologic adverse reactions to clopidogrel. This has important therapeutic implications, as premature discontinuation of clopidogrel is the strongest risk factor for stent thrombosis. Clopidogrel allergy most commonly manifests as a rash. It is important to distinguish this from other causes of rash occurring in patients who have had a recent coronary stent. Although antihistamines and short-term oral corticosteroids are effective in treating most clopidogrel hypersensitivity reactions, some persistent reactions may require discontinuation of clopidogrel. When discontinuation of clopidogrel is required, substitution with an alternative thienopyridine such as ticlopidine traditionally has been performed. However, a recent study suggests that there may be as high as a 27% risk of recurrence of non-life-threatening allergic reactions in such patients, which are usually similar to the allergic reactions that occurred with clopidogrel. No data are available regarding the frequency of cross-reactivity to prasugrel and ticagrelor; these may be potential therapeutic options in some patients.
Background-Clopidogrel and ticlopidine are structurally very similar. In patients with an allergic or hematologic adverse reaction to either one of these drugs, the likelihood that an allergic or hematologic adverse effect will develop to the other is unknown. It is also unknown whether a reaction to the second thienopyridine is likely to be life threatening. Methods and Results-Medical records from 2 academic institutions were reviewed to identify patients who had an allergic or hematologic adverse reaction to either of the 2 currently commercially available thienopyridines and who were subsequently prescribed the other thienopyridine. Patient demographics, details of the adverse reactions, and subsequent clinical course were reviewed. A total of 76 patients were identified with an allergic or hematologic adverse reaction to clopidogrel or ticlopidine who had also received the other thienopyridine. Fourteen (27%; 95% CI, 16 to 41) patients who had an allergic or hematologic adverse reactions to clopidogrel had a similar reaction to ticlopidine; none developed a life-threatening reaction. The most common reaction was a rash (93%). Conclusions-In patients with an allergic or hematologic adverse reaction to one thienopyridine, there seems to be an increased frequency of such reactions to the other thienopyridine. However, no patient had a life-threatening reaction after exposure to the alternative thienopyridine. Clinical Perspective on p 351Clopidogrel, a second-generation thienopyridine structurally similar to ticlopidine, was developed to be equally efficacious to ticlopidine but with fewer adverse effects. 4,5 However, allergic or hematologic reactions occur in approximately 1% of patients taking clopidogrel and, when severe, require discontinuation. 6 Substituting ticlopidine for clopidogrel is the most common practice in patients who develop a severe allergic or hematologic adverse reaction to clopidogrel. However, the frequency and severity of allergic cross-reactivity between the agents are not known. Methods PatientsThe electronic health records from the Geisinger Clinic (Danville, Pa) and the Mayo Clinic (Rochester, Minn) were reviewed to identify patients older than 18 years with an allergy to a thienopyridine in their medical record between January 1995 and June 2007. These patients were sorted into 3 groups based on whether their allergy was either to 1 of the 2 currently available thienopyridines or to both. Of the patients with an allergy to only one thienopyridine, only those who had also received the other thienopyridine, as determined by a query of their electronic medication lists, were selected for inclusion in this analysis. These medication lists include all medications prescribed by all physicians throughout the Geisinger or Mayo systems and are reconciled at each clinic visit with those the patient is actually taking. For each patient thus identified, medical records were reviewed to assess adverse reaction details and subsequent clinical course. Only patients whose adverse reactions met t...
We describe two cases in which three-dimensional echocardiography provided unique anatomical data. This information enhanced the diagnostic power of two-dimensional echocardiography by improving confidence in interpretation and by providing distinctive spatial insights.
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