Betalactam antibiotics are the most frequent cause of hypersensitivity reactions to drugs mediated by a specific immune mechanism. Amoxicillin (AX) is the most often elicitor, which was originally prescribed alone, and is now often prescribed alongside clavulanic acid (CLV). After the administration of AX-CLV, there are subjects who develop AX allergy whilst tolerating CLV, whilst for others the opposite occurs. To our knowledge, there are no clinical reports of patients with IgE-mediated allergy to both AX and CLV.
Skin testing was performed by skin prick test and if negative followed by intradermal test. Serum specific IgE determination was performed by ImmunoCAP and basophil activation test (BAT) was performed by flow cytometry. Single blind placebo controlled drug provocation test was performed to assess tolerance to other penicillins.
Case 1: 48 year-old woman who developed urticaria and angioedema 45 min after the oral administration of AX-CLV. Case 2: 43 year-old woman who developed systemic pruritus with generalised urticaria and facial and tongue angioedema 15 min after the oral administration of AX-CLV. The allergological work-up indicated that the two patients were allergic to both AX and CLV with good tolerance to BP and penicillin V. Both patients gave positive skin test results to AX and CLV, showed specific anti-AX IgE and gave positive BAT results to AX and CLV.
Our study provides evidence that sensitization to both AX and CLV can appear in the same patient. To our knowledge this is the first study showing this sensitization pattern.