P2.115: Incidence of Anaphylaxis in Pediatric Patients with Documented Penicillin Allergy Receiving a Single Antibiotic: A PHIS-Based Analysis (2017–2024)

Background: Penicillin allergy is one of the most commonly reported drug allergies in pediatric populations and frequently leads to avoidance of beta-lactam antibiotics, even when alternative treatments may be less effective or more toxic. However, most penicillin allergy labels are not confirmed by testing and do not represent true IgE-mediated hypersensitivity. The most severe manifestation of such allergy is anaphylaxis, typically requiring intramuscular epinephrine for treatment. This study evaluates the incidence of epinephrine administration—a surrogate for anaphylaxis—among hospitalized children with documented penicillin allergy who received one of five specific antibiotics, excluding those who received ampicillin or multiple concurrent antibiotics.

Methods: We conducted a retrospective cohort analysis using data from the Pediatric Health Information System (PHIS) between 2017 and 2024. We included pediatric inpatients with a documented penicillin allergy who received only one of the following antibiotics: amoxicillin-clavulanate (Augmentin), piperacillin-tazobactam (Pip-Tazo), ampicillin-sulbactam (Unasyn), ceftriaxone (CTX), or doxycycline. Patients who received ampicillin or more than one antibiotic were excluded. The primary outcome was epinephrine administration during hospitalization, used as a proxy for anaphylaxis. Incidence of epinephrine use was calculated overall and for each antibiotic group.

Results: A total of 25,726 pediatric patients met inclusion criteria. Of these, 1,239 patients (4.82%) received epinephrine, suggestive of possible anaphylactic reactions.
The breakdown by antibiotic is as follows:
Augmentin: 611 patients; 29 received epinephrine (4.75%)
Zosyn: 1,479 patients; 110 received epinephrine (7.44%)
Unasyn: 654 patients; 49 received epinephrine (7.49%)
CTX (Ceftriaxone): 21,574 patients; 999 received epinephrine (4.63%)
Doxycycline: 1,408 patients; 52 received epinephrine (3.69%)
These results suggest that while most patients tolerated these medications without significant adverse reactions, there is a measurable incidence of epinephrine use particularly higher in patients receiving Pip-Tazo and Unasyn.

Conclusion: In this multicenter pediatric cohort, the overall incidence of possible anaphylaxis—as indicated by epinephrine use—was 4.82% among patients receiving a single antibiotic (excluding ampicillin and combination therapy). The statistically significant variation in epinephrine use across antibiotics highlights the importance of accurate allergy documentation, risk stratification,