PROlonged versus Single dose in PEnicillin oral Challenge Testing

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Penicillin allergies are a major burden on patients and health care worldwide. Currently, up to 1 in 4 hospitalised patients admitted to hospital will report an antibiotic allergy, which limits appropriate antibiotic use and leads to poorer health outcomes. In some instances, patients can be given a single or multiple test dose of an antibiotic to determine if a patient is truly allergic. This study will inform whether research to determine if a multiple dose challenge (5-days) elicits more true penicillin allergy than a single dose challenge is feasible. The current Drug Allergy Practice Parameters recommend “against the routine use of multiple-day challenges in the evaluation of penicillin allergy”, providing a “strong recommendation” but with ” low certainty of evidence”. In Europe, a mixture of observational and retrospective studies has suggested that extended challenges ranging from 3 to 10 days may be superior to single dose challenges at excluding delayed immune reactions, however the reported prevalence of delayed reactions is highly variable (5-12% of patients) and many were reliant on patient self-reporting. This is converse to the North American experience where delayed prolonged challenges have been associated with low rates of delayed reactions (0-1.8%). Whilst a study of children demonstrated that delayed reactions may occur <7 days following a single challenge. Therefore, whilst oral challenge is the well-defined gold standard for penicillin allegro-immunological investigation, limited controlled evidence is available regarding the safety and efficacy of single dose versus prolonged oral challenge. Blinded randomized placebo-controlled trials have not been previously used in any drug allergy trials. The aim of this double blinded placebo controlled pilot randomised control trial is to evaluate the feasibility of placebo controlled trial and safety of oral penicillin challenge (5-day) versus single dose challenge penicillin challenge (followed by 5 day placebo) for evaluation of immune-mediated penicillin allergy in the inpatient and outpatient setting to inform the design of a definitive trial.