SYSTEMIC REACTIONS TO SUBCUTANEOUS IMMUNOTHERAPY TREATED WITH EPINEPHRINE: A CANADIAN EXPERIENCE

Introduction Subcutaneous immunotherapy (SCIT) is associated with a risk of systemic reactions. While previous studies have attempted to quantify this risk, Canadian data is lacking. We aimed to quantify and characterize SCIT systemic reactions requiring epinephrine administration in a Canadian setting. Methods We performed a retrospective chart review of patients with reactions to SCIT requiring intramuscular epinephrine from January 2011 to October 2017 at a single allergy practice in Canada. The 2010 WAO grading system was used to grade the reactions. Results 380 patients were on SCIT and there were a total of 29,334 injection visits. 28 (7.37%) patients required epinephrine administration (incidence rate of 1 in 1,047 injection visits or 0.095%). The age range was from 8 to 60 years (median 34 years). There were 19 (68.9%) males and 4 patients were younger than 18. 11 patients had asthma. No patients were on beta-blockers. All the injections were from vial #4 (most concentrated). Five (17.9%) patients reacted to the first shot of a new serum. Two reactions occurred more than 30 minutes after the injection. Three (10.7%) patients experienced grade 4 reactions. Of these, 2 had asthma and 1 had food allergies. Two patients with grade 4 reactions reacted to the first injection from a new vial. All 3 reactions occurred within 30 minutes of the injection. There were no fatalities. Conclusions To our knowledge, this is the first retrospective chart review of patients with SCIT reactions in Canada. Our findings provide a Canadian perspective and complement the available data on SCIT related reactions.