Overview of allergic mechanisms. Ebastine has more than an antihistamine effect

Histamine antagonists together with topical steroids are the treatment of choice in allergic rhinitis. Many of these histamine antagonists exhibit effects in addition to blockade of the histamine receptor. In this study we have investigated the effects of ebastine and carebastine on the release of eicosanoids and cytokines from human dispersed polyp cells and the effect of these compounds on the release of inflammatory mediators into nasal lavage fluid after allergen challenge. Ebastine was shown to block the release of anti-IgE-induced prostaglandin D2 (PGD2) and leukotriene C4/D4 from human nasal polyp cells (IC30 values of 2.57 and 9.6 mumol/L, respectively) and to inhibit the release of cytokines. Carebastine inhibited the release of PGD2 (IC30 8.14 mumol/L) but had little effect on cytokine release. When patients underwent nasal provocation tests with allergen, ebastine significantly increased the mean number of pollen grains required to induce an allergic response. In addition, the drug inhibited the release of granulocyte-macrophage colony-stimulating factor but had no effect on any other mediators measured.