original article Wien Klin Wochenschr https://doi.org/10.1007/s00508-019-1499-0 Incidence, etiology, predictors and outcomes of suspected drug hypersensitivity reactions in a tertiary care university hospital’s emergency department A retrospective study Cvijeta Bielen · Luka Bielen · Robert Liki ´ c Received: 11 May 2018 / Accepted: 8 April 2019 © Springer-Verlag GmbH Austria, part of Springer Nature 2019 Summary Background Allergic drug reactions are adverse drug reactions that result from a specific immunologic re- sponse to a medication. Considering the epidemio- logical and clinical importance of drug allergy, this retrospective analysis focused on drug hypersensitiv- ity in a tertiary care university hospital emergency de- partment (ED). Methods In this study 74,929 ED records obtained from March 2012 to March 2015 were reviewed to de- termine the incidence, etiology, predictors and clinical features of drug hypersensitivity. Results The observed incidence of drug hypersen- sitivity was 0.87% of all ED admissions. It was sig- nificantly higher in female patients aged 18–29 years (2.26%; P < 0.0001) and during winter months (1.09%; P = 0.0058). Most patients had mild to moderate Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00508-019-1499-0) contains supplementary material, which is available to authorized users. C. Bielen IQVIA Zagreb d.o.o., Radnicka cesta 80/17, 10000 Zagreb, Croatia L. Bielen Department of Internal Medicine, Intensive Care Unit, University Hospital Centre Zagreb, Kispaticeva 12, 10000 Zagreb, Croatia R. Liki´ c, MD, PhD () Department of Internal Medicine, Unit of Clinical Pharmacology, University Hospital Centre Zagreb, Kispaticeva 12, 10000 Zagreb, Croatia RobertLikic@inet.hr L. Bielen · R. Liki´ c, MD, PhD School of Medicine, University of Zagreb, Zagreb, Croatia symptoms which regressed following ED treatment. Only five patients (7 per 100,000 ED visits) were di- agnosed with drug-induced anaphylaxis, and only five patients were provisionally diagnosed with se- vere non-immediate reactions with systemic involve- ment. No patient died of drug hypersensitivity in the ED, and only a small proportion required subse- quent hospitalization. The most common causes of drug hypersensitivity reactions were amoxicillin and paracetamol. Conclusion Drug hypersensitivity is a common rea- son for tertiary centre emergency admissions. This is the largest analysis of ED drug hypersensitivity ad- missions so far. Beta-lactams were identified as the leading cause of drug hypersensitivity requiring ED evaluation, which also explains the peak of drug hy- persensitivity cases during winter months when the use of these medications is highest. Keywords Drug hypersensitivity · Emergency department · Beta-lactam antibiotics · Anaphylaxis · Serious non-immediate reactions with systemic involvement · Adverse drug reaction · Paracetamol Introduction Drug hypersensitivity reactions are generally un- expected and unpredicted adverse drug reactions (ADRs) in response to normal therapeutic doses of a drug. They may be of non-immunologic nature, so-called pseudoallergic or intolerance reactions, or of drug-specific immunologic nature. The clinical picture does not enable a safe and proven distinction between them. True allergic drug reactions are ADRs where the immune system is previously involved in a sensitization phase and manifest on a new con- K Incidence, etiology, predictors and outcomes of suspected drug hypersensitivity reactions in a tertiary care. . .