Impact of Outpatient Antihypertensive Medication Use on Epinephrine Resistance in Anaphylaxis

Background: There has been an increase in allergy-related emergency department (ED) visits over the past several years. Underlying cardiovascular disease or respiratory disease and concurrent beta blocker or angiotensin-converting enzyme inhibitor use have been identified as potential risk factors for severe or refractory anaphylactic reactions. Conflicting evidence exists regarding the association between antihypertensive (AH) use and the incidence of refractory anaphylaxis. Objective: The purpose of this study was to determine the incidence of refractory anaphylaxis in patients presenting to the ED while prescribed select AH medications outpatient. Methods: This was a retrospective cohort study of all adult and pediatric patients presenting to the ED between February 16, 2021, and August 31, 2021, with a diagnosis of anaphylaxis. The primary objective was to compare the proportion of patients experiencing refractory anaphylaxis that were prescribed versus not prescribed AH medications in the outpatient setting. Results: A total of 101 patients were treated for anaphylaxis in the ED during the study timeframe with 13 patients in the AH group and 88 patients in the no AH group. There was no difference in the incidence of refractory anaphylaxis between groups (0% vs 9%; p=0.48). Significantly fewer patients in the AH group required any epinephrine doses compared to the no AH group (38% vs 88%; p<0.001). Conclusions: Outpatient use of select AH medications was not associated with an increased incidence of refractory anaphylaxis in patients presenting to the ED.