Lerario MP, Grotta JC, Merkler AE, et al. - Using inpatient and outpatient claims between 2008 and 2015 from a nationally representative 5% sample of Medicare beneficiaries, the authors carried out a retrospective cohort study to ascertain if individuals with stroke who receive thrombolytic agents face a higher risk of anaphylaxis than those who do not receive thrombolytics. The sample consisted of patients who were ≥ 65 years old and hospitalized with acute ischemic stroke, defined by validated International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes. Of the 66,989 stroke patients, the 3,176 who had intravenous thrombolysis more frequently had atrial fibrillation and more frequently received intravenous contrast dye but were otherwise comparable in terms of demographics and comorbidities. Although an uncommon event, the risk of anaphylaxis was significantly higher among those undergoing intravenous thrombolysis among patients with acute ischemic stroke.