Cross-reactivity and Tolerability of Ertapenem in Patients with IgE-Mediated Hypersensitivity to Β-Lactams.

Background and Objective: Administration of carbapenems to beta-lactam-allergic patients has always been considered potentially harmful because of a 47.4% rate of cross-reactivity to imipenem reported in a single study. Nevertheless, recent studies have shown that the rate of cross-reactivity of imipenem and meropenem with penicillins is lower than 1%. The aim of this study was to evaluate the possibility of using ertapenem in patients with an established IgE-mediated beta-lactam allergy.Patients and Methods: We studied all participants who came to our allergy unit and had a clinical history of immediate hypersensitivity reactions to beta-lactams. The inclusion criteria were a positive skin test result to at least 1 beta-lactam molecule and/or positive specific IgE (when available). All participants underwent immediate-type skin tests with several p-lactam molecules including ertapenem. Challenges with intravenous ertapenem were performed on 2 different days in patients with negative skin test results.Results: We examined 49 patients with a clinical history of immediate reactions to beta-lactams. All the patients had positive skin tests and/or positive specific IgE to at least 1 beta-lactam reagent and negative carbapenem skin tests. Thirty-six patients agreed to undergo the challenges and 35 tolerated the full dose of ertapenem.Conclusions: The practice of avoiding carbapenems in patients with beta-lactam allergy should be abandoned considering the very low rate of cross-reactivity. beta-Lactam-allergic patients who need ertapenem therapy should undergo skin tests and, if negative, a graded challenge to assess tolerability.