ALLERGIC REACTIONS TO AMPICILLIN - STUDIES ON THE SPECIFICITY AND SELECTIVITY IN SUBJECTS WITH IMMEDIATE REACTIONS

Background Ampicillin (AMP) is a drug that has been prescribed extensi vely. Reactions that have been reported include exanthema, desquamativ e contact eczema, urticaria and anaphylaxis. Experimental evidence ind icates that the side chain of AMP is a structure that may induce a sel ective immune response either at the humoral or lymphocyte T-cell leve l. With regard to IgE reactions, the selectivity and specificity of th e response needs to be studied in humans. Objectives To study the spec ificity of the IgE response in a group of subjects who had an immediat e allergic reaction after the administration of AMP. Methods Subjects developing an immediate response (anaphylaxis or urticaria) after the administration of AMP or an aminopenicillin derivative with the same s ide chain as AMP were studied. Skin tests were made to determinants ge nerated from benzyl penicillin (BP): benzyl penicilloyl (BPO) and mino r determinant mixture (MDM), as well as amoxicillin (AX) and AMP. Spec ific IgE antibodies were determined to benzyl penicilloyl polylisine ( BPO-PLL), amoxicilloyl-polylisine (AX-PLL) and ampicilloyl-polylisine (AMP-PLL). The specificity of the IgE antibody response was studied by RAST and RAST inhibition. Subjects were classified in three categorie s: group A: those who were skin test and/or RAST positive to determina nts derived from benzylpenicllin, group B: those who were negative to determinants derived from benzylpenicillin but were skin test and/or R AST positive to determinants derived from AX and AMP and group C: thos e who were exclusively positive to determinants derived from AMP. Resu lts A total of 48 subjects was included in the study. In group A there were 35 cases, in group B 10 cases, and in group C three cases. RAST inhibition studies showed that in some instances the side chain of AMP could induce specific responses with a variable degree of crossreacti vity between BP and AX. Conclusions Athough AMP can induce an immediat e IgE response in subjects allergic to betalactams and the structure o f the side chain may contribute to the specificity of the response, ou r results indicate that in most instances crossreactivity with the oth er penicillins exists and that in the groups studied selective reactio ns to just AMP derived determinants were uncommon.