Abstract
BACKGROUND/AIMS: Drug hypersensitivity reactions (DHRs) are unpredictable adverse drug reactions that can present with varied clinical manifestations, including anaphylaxis. However, data on DHRs initially diagnosed in the emergency department (ED) and subsequently confirmed by allergy specialists remain limited. This study investigated the clinical characteristics of ED-diagnosed DHRs and the outcomes of culprit-drug identification during outpatient allergy follow-ups. METHODS: We retrospectively analyzed adverse drug reaction reports from the ED of a university hospital in Korea between January 2021 and December 2023. Cases meeting the World Health Organization-Uppsala Monitoring Center criteria for DHRs were included. Clinical features, suspected culprit drugs, reaction phenotypes, severity, and outpatient follow-up outcomes were evaluated. RESULTS: Among 668 patients (mean age 43.3 yr), 63.9% had immediate-type and 36.1% had delayed-type reactions. Radiocontrast media, nonsteroidal anti-inflammatory drugs (NSAIDs), and β-lactams were the most common suspected culprits. Cutaneous manifestations predominated in both immediate- and delayed-type reactions. Anaphylaxis occurred in 33.5% of the immediate-type reactions and was significantly associated with allergic comorbidities. Outpatient follow-up was completed in only 12.9% of patients, and a culprit drug was identified in 59.3% of those patients by history, specific IgE, skin testing, or drug provocation. The most frequently confirmed causative agent was cefaclor, followed by amoxicillin/amoxicillin- clavulanate, NSAIDs, and eperisone. CONCLUSION: Immediate-type DHRs were the predominant presentation in the ED and were predominantly caused by radiocontrast media and NSAIDs. Given the low rate of outpatient follow-up, early referral to allergists is essential to improve patient safety and prevent reexposure.