Antiallergic activity of tiaramide (RHC 2592-A).

Tiaramide (RHC 2592-A) is an analgesic agent with antiallergic activity in vivo. We have investigated the antianaphylactic properties of tiaramide and its metabolites in three in vitro models of anaphylaxis; namely, IgE-induced release of histamine from rat mast cells and human basophils, and IgG1-induced release of histamine from guinea pig lung slices. Tiaramide and one of the metabolites, desethanol tiaramide (DETR), were found to inhibit immunologic release of histamine in all three of these in vitro models. Although tiaramide and DETR were less potent than disodium cromoglycate (DSCG) and/or proxicromil as inhibitors of mediator release, they were not cross-tachyphylactic to DSCG in the rat mast cell model. These data indicate that tiaramide is a unique inhibitor of histamine release whose mechanism of action differs from that of DSCG, and which in vivo is converted to a more potent metabolite.