Immediate allergic reactions to penicillins: unanswered questions.

PURPOSE OF REVIEW: Penicillins and other beta-lactam antibiotics are the most frequent drugs involved in allergic drug reactions. Our aim was to outline major questions regarding immediate hypersensitivity reactions with a special focus on amoxicillin, a drug that can induce selective responses, and on the common determinants shared by all penicillins, the structure formed by the beta-lactam ring bound to proteins. This review analyzes recent research and contextualizes the findings in relation to the previous literature, which we define as the classical model. This includes an analysis of antibiotic prescription patterns, clinical entities induced by specific immunoglobulin E antibodies, other proposed mechanisms involved in immediate reactions, and the value of diagnostic tests including drug provocation.

RECENT FINDINGS: Amoxicillin, alone or in combination with the beta-lactamase inhibitor clavulanic acid, is the most frequent penicillin involved in hypersensitivity drug reactions in many countries. Early reports of this pattern from Spain have been and continue to be confirmed by other groups. Analysis of the recent literature shows the complexity of this area, notwithstanding the findings of earlier studies, which mainly focused on allergy to penicillin based on the classical concept of major and minor determinants of benzyl penicillin.

SUMMARY: The amoxicillin model, together with other drugs in the penicillin group, provides relevant information about what is known and what questions must be addressed in future research on beta-lactam allergies.