Improving the preparation and delivery of antibiotic allergy skin testing
Published online November 6, 2024
Skin testing (ST) is the most widely accepted method used to assess for potential sensitization in patients with suspected immunoglobulin type E-mediated allergic reactions to antibiotics. ST involves the administration of tiny amounts of diluted reagents containing the suspected antibiotics that are injected either under the skin (skin prick test) or within the layers of the skin (intradermal test). Multiple reagents for ST are typically prepared by doctors, nurses or pharmacists on the day of testing. The preparation of ST reagents is time-consuming and resource-intensive, and susceptible to calculation, dilution, and preparation errors, particularly in the presence of distractions, such as when preparing ST reagents at the bedside. Preparation of ST reagents ahead of time will improve patient safety and the delivery of antibiotic ST. Additionally, it will improve cost-effectiveness through a reduction in drug wastage and time undertaken to prepare ST reagents for multiple patients at once. However, appropriate stability data that allow the preparation of ST reagents ahead of time is so far limited to only a small number of penicillin-based antibiotics.
In a recent study published in The Journal of Allergy and Clinical Immunology: In Practice, Wanandy, Handley and colleagues determined the physical and chemical stability of ST reagents consisting of 16 antibiotics from 7 different classes. The investigators used a common analytical technique called high performance liquid chromatography for chemical stability assessment, and absence of precipitations or haziness, large pH shift, and change in color of the ST reagents to assess physical stability.
The study found that most of the antibiotics studied were chemically and physically stable for between 2 and 7 days when prepared into ST reagents. Penicillin antibiotics amoxicillin and ampicillin were stable for 2 days when diluted in water for injection and stored in glass vials, while benzylpenicillin, flucloxacillin, and the combination of piperacillin and tazobactam were stable for at least 2 days when stored in either glass vials or plastic syringes. Most of the cephalosporin antibiotics studied remained stable for at least 2 days when stored in either glass vials or plastic syringes, except for cefotaxime, which was only stable for 1 day when stored in glass vials but remained stable for at least 2 days when stored in plastic syringes. Aztreonam, ciprofloxacin, and vancomycin remained stable for 7 days, while meropenem was stable for 2 days when stored in either glass vials or plastic syringes. The combination of sulfamethoxazole and trimethoprim lost a significant quantity of the sulfamethoxazole component when stored in plastic syringes but remained stable for at least 2 days when stored in glass vials. The combination of amoxicillin and clavulanic acid was unstable and must be prepared fresh on the day of testing and used immediately.
In summary, the study provides clinically relevant and practical recommendations on appropriate components, dilution, storage containers and shelf-life allowing 15 antibiotics to be prepared as ST reagents ahead of time, improving the delivery of antibiotics for ST.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.
Full Article