Abstract
Cross-reactivity between aztreonam and penicillins is poor, but clinical tolerance of aztreonam has been assessed, by means of tolerance challenge tests, only in a few groups of penicillin-allergic patients. The aim of this study is to evaluate the tolerability of aztreonam in a large group of betalactam-allergic patients. We studied all patients (> 14 years of age), with a clinical history of immediate reactions to any betalactam and with positive immediate-type skin tests and/or positive specific IgE to any of the studied betalactam; they were studied by means of: skin prick and intradermal tests with penicilloyl polysine, minor determinant mixture, semisynthetic penicillins, cephalosporins, aztreonam and imipenem; detection of specific IgE to penicillin G, penicillin V, ampicillin, amoxicillin, cefaclor and ceftriaxone. Patients with negative immediate-type skin tests with aztreonam then underwent a graded intramuscular challenge. Forty-five patients (mean age 46.1 ± 15.2 years), 27 females and 18 males, had positive skin tests and/or specific IgE to at least one of the studied betalactams. The most involved drugs were amoxicillin (23 cases), ampicillin (9 cases), penicillin G (8 cases) and other betalactams in the remaining cases. The most frequent reactions were anaphylaxis (27 cases) and urticaria (15 cases). All patients had negative intradermal tests with aztreonam and all patients tolerated the intramuscular graded challenge. Our data confirm the lack of cross-reactivity between betalactams and aztreonam. Immediate-type skin tests with aztreonam represent a simple and rapid diagnostic tool to establish tolerability in betalactam-allergic patients who urgently need this drug.