Drugs as allergens: the molecular basis of IgE binding to thiopentone.

Using an immunoassay developed for the detection of thiopentone-reactive IgE antibodies, the combining site specificities of such antibodies found in sera of patients who experienced life-threatening anaphylactic reactions to the drug were studied. The antibody combining sites from one patient were complementary to the region of the thiopentone molecule containing a thio group at position 2 of the barbiturate ring. The allergenic determinant recognized by IgE antibodies from another patient encompassed a secondary pentyl group and an ethyl group attached to position 5 on the other side of the barbiturate ring. Thus, it is already clear that there is more than one allergenic determinant on the thiopentone molecule with the capacity to provoke IgE formation and drug-induced allergic reactions.