Cross-Reactivity in Betalactam Allergy: Alternative Treatments

It was originally thought that, as all betalactams share a four-member ring, they would cross-react, and so the classical recommendation was for allergic patients to avoid all betalactams. However, later studies found that some individuals selectively responded to one betalactam only and tolerated others. This was shown to be more frequent than initially thought, and this finding has led to a change from the initial recommendations of complete avoidance. Selective responses to amoxicillin are mainly due to recognition of the side chain structure, making benzylpenicillin a safe alternative. These amoxicillin-selective responders comprise up to 55 and 90 % of patients with immediate allergic reactions to amoxicillin and amoxicillin-clavulanic, respectively. Additionally, more than 85 % of penicillin-allergic patients can tolerate cephalosporins with different R1 side chains, decreasing to 65 % if the side chain is identical. It is known that third and fourth generation cephalosporins are well tolerated by penicillin-allergic patients, probably because their chemical structures differ more from penicillins that those from the first generation. In patients with IgE-mediated allergic reactions to cephalosporins, penicillins can be an alternative treatment in up to 75 % of cases. Moreover, 40 % of patients primarily sensitized to a given cephalosporin also react to others, which might be because some cephaloporins have the same (ceftriaxone and cefotaxime) or very similar (ceftriaxone and cefuroxime) side chain structures. Finally, carbapenems and monobactams are good alternative for patients with penicillin and/or cephalosporin allergy because cross-reactivity occurs in <1 % of these cases. For all betalactams, tolerance is higher in T-cell-mediated reactions than IgE-mediated. These results show that alternative treatments for infectious disease are available to patients with allergic reactions to betalactams, from within the same group of antibiotics. Nevertheless, this general rules need to be analyzed patient by patient, and skin tests and graded challenge with the betalactam that is going to be administered are recommended. Keypoints • Patients with IgE- or T-cell-mediated allergy to betalactams can have selective reactions, specific to one betalactam with good tolerance to others, or be cross-reactive, recognizing several different chemically related betalactams. • The percentage of selective reactions to the different betalactam compounds is higher than previously reported and patients should be studied in order to increase the treatment options available. © 2015, Springer International Publishing AG.