* Immediate allergic reactions to amoxicillin

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Abstract
A large group of patients with suspected allergic reactions to (β‐lactam antibiotics was evaluated. A detailed clinical history, together with skin tests, RAST (radioallergosorbent test), and controlled challenge tests, was used to establish whether patients allergic to β‐lactam antibiotics had selective immediate allergic responses to amoxicillin (AX) or were cross‐reacting with other penicillin derivatives. Skin tests were performed with benzylpenicilloyl‐poly‐L‐lysine (BPO‐PLL), benzylpenicilloate, benzylpenicillin (PG), ampicillin (AMP), and AX. RAST for BPO‐PLL and AX‐PLL was done. When both skin test and RAST for BPO were negative, single‐blind, placebo‐controlled challenge tests were done to ensure tolerance of PG or sensitivity to AX. A total of 177 patients were diagnosed as allergic to β‐lactam antibiotics. We selected the 54 (30.5%) cases of immediate AX allergy with good tolerance of PG. Anaphylaxis was seen in 37 patients (69%), the other 17 (31%) having urticaria and/or angioedema. All the patients were skin test negative to BPO; 49 of 51 (96%) were also negative to MDM, and 44 of 46 (96%) to PG. Skin tests with AX were positive in 34 (63%) patients. RAST was positive for AX in 22 patients (41%) and to BPO in just 5 (9%). None of the sera with negative RAST for AX were positive to BPO. Challenge tests with AX were performed in 23 subjects (43%) to establish the diagnosis of immediate allergic reaction to AX, and in 15 cases (28%) both skin test and RAST for AX were negative. PG was well tolerated by all 54 patients. We describe the largest group of AX‐allergic patients who have tolerated PG reported so far. Diagnosis of these patients can be achieved only if specific AX‐related reagents are employed. Further studies are necessary to determine the exact extent of this problem and to improve the efficacy of diagnostic methods.