Deconstructing adverse reactions to Amoxicillin-Clavulanic Acid: the importance of time of onset

• Published in: Journal of investigational allergology & clinical immunology Vol. 34; no. 3
• Main Authors: Freundt-Serpa, N P, Salas-Cassinello, M, Gonzalo-Fernández, A, Marchán-Pinedo, N, Doña, I, Serrano-García, I, Humanes-Navarro, A M, Bogas, G, Labella, M, Sánchez-Morillas, L, Torres, M J, Fernández-Rivas, M
• Format: Journal Article
• Language: English
• Published: Spain 21.02.2023
• Subjects: Amoxicillin-Clavulanic acid; Immediate reaction; Intradermal test; Drug allergy; Non-immediate reaction
• ISSN: 1018-9068
• DOI: 10.18176/jiaci.0896

Amoxicillin-clavulanic acid (AX-CL) is the most consumed betalactam antibiotic worldwide. We aimed to establish the different phenotypes of betalactam allergy in those referring a reaction with AX-CL and to investigate the differences between immediate and non-immediate onset. Cross-sectional retrospective study performed at Hospital Clínico San Carlos (HCSC) and Hospital Regional Universitario de Málaga (HRUM) in Spain. Patients reporting reactions with AX-CL who completed the allergy workup between 2017 and 2019 were included. Data of reported reaction and allergy workup were collected. Reactions were classified as immediate and non-immediate with 1hour cut-off point. We included 372 patients (HCSC 208, HRUM 164). There were 90 (24.2%) immediate, 252 (67.7%) non-immediate reactions, and 30 (8.1%) with unknown latency. Allergy to betalactams was ruled-out in 266 (71.5%) and confirmed in 106 patients (28.5%). The final main diagnosis in the overall population were allergy to aminopenicillins (7.3%), to CL (7%), to penicillin (6.5%) and to betalactams (5.9%). Allergy was confirmed in 77.2% and 14.3% of immediate and non-immediate reactions respectively, with a relative risk of 5.06 (95%CI 3.64-7.02) of an allergy diagnosis in those reporting immediate reactions. Only 2/54 patients with late-positive intradermal test (IDT) to CL were diagnosed of CL allergy. Allergy diagnosis was confirmed in a minority of the whole study population, but 5 times more frequently in those reporting immediate reactions, making this classification useful in risk stratification. Late-positive IDT for CL has no diagnostic value and its late reading could be retrieved from the diagnosis work-up.