The effect of ranitidine, alone and in combination with clemastine, on allergen-induced cutaneous wheal-and-flare reactions in human skin

Abstract

The effect of intradermal ranitidine (administered alone and in combination with clemastine) on allergen-mediated wheal-and-flare reactions has been evaluated in a double-blind study on 10 healthy atopic volunteers. Ranitidine alone, administered in doses over a 10 4-fold concentration range, had no effect on the size either of allergen-induced wheal or flare reactions. Clemastine alone evoked a dose-related inhibition of both wheal and flare. Compared to the inhibition achieved by clemastine alone, the combination of ranitidine with clemastine produced a small but significant increase in inhibition of allergen-induced flare at ranitidine concentrations of 10 −5 mol/L ( p < 0.001) and 10 −6 mol/L ( p < 0.01), and of allergen-induced wheal at ranitidine concentration 10 −5 mol/L ( p < 0.01). Our results provide further evidence for the presence of cutaneous histamine H 2 receptors and their participation in the formation of allergen-mediated skin reactions but indicate that the contribution of cutaneous histamine H 2-receptor stimulation to the production of immediate wheal-and-flare reactions evoked by allergen is only modest.