ABSTRACT
Betalactams are the most frequent cause of hypersensitivity reactions to drugs mediated by a specific immune mechanism. Immediate reactions occur within 1 to 6 hours after betalactam administration, and are generally IgE-mediated. They clinically translate into urticaria, angioedema and anaphylaxis. Non-immediate or delayed reactions occur after 1 hour of administration. These are the most common reactions and are usually mediated by T cells. The most frequent type is the maculopapular or morbilliform exanthematous eruption. Most individuals who report allergies to penicillin and betalactams can tolerate this group of antibiotics. To make diagnosis, a detailed medical history is essential to verify whether it was an immediate or non-immediate reaction. Thereafter, in vivo and/or in vitro tests for investigation may be performed. The challenging test is considered the gold standard method for diagnosis of betalactam hypersensitivity. The first approach when suspecting a reaction to betalactam is to discontinue exposure to the drug, and the only specific treatment is desensitization, which has very precise indications. The misdiagnosis of penicillin allergy affects the health system, since the “penicillin allergy” label is associated with increased bacterial resistance, higher rate of therapeutic failure, prolonged hospitalizations, readmissions, and increased costs. Thus, it is essential to develop strategies to assist the prescription of antibiotics in patients identified with a label of “betalactam allergy” at hospitals, and to enhance education of patients and their caregivers, as well as of non-specialist physicians.
Beta-lactams/adverse effects; Penicillins/adverse effects; Anti-bacterial agents/adverse effects; Drug hypersensitivity/diagnosis
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Source: Adapted from Castells M, Khan DA, Phillips EJ. Penicillin allergy. N Engl J Med. 2019;381(24):2338-51. Review.(14)
Source: Adapted from Castells M, Khan DA, Phillips EJ. Penicillin allergy. N Engl J Med. 2019;381(24):2338-51. Review.(14)
* In severe immediate reactions (anaphylaxis), measure serum specific IgE levels before skin test; ‡ skin tests are usually conducted by trained allergy/immunology specialists, in a suitable setting; † evaluation by allergist can be performed at any time for correct diagnosis, but it is mandatory in cases of already confirmed allergy, in particular for investigation of cross-reactivity between different betalactams, and safe release of class options; # the severe non-immediate reactions include acute generalized exanthematous pustulosis, drug reaction with eosinophilia, systemic symptoms, Stevens Johnson syndrome, toxic epidermal necrolysis, and the organ-specific reactions (hepatitis, nephritis, hematological, etc.).BL: betalactams.