The in vivo inhibitory effect of a new antiallergic, anti-H1 drug, cetirizine, on eosinophil attraction at skin sites challenged with various stimuli has been recently suggested. In the present work, we confirmed that this molecule, at therapeutical concentration, has a potent inhibitory action on eosinophil response to different chemoattractant mediators such as platelet-activating factor (PAF acether) and N-formyl methionyl leucyl phenyl alanyl in vitro. Another anti-H1 drug, polaramine, did not show this effect at the same concentration. These findings suggest that cetirizine in addition to its antihistaminic effect could also play a direct inhibitory effect on eosinophil recruitment. Moreover, cetirizine was not toxic for eosinophils and did not induce degranulation, as shown by the absence of peroxidase release. Comparison between cetirizine and a PAF acether antagonist (BN 52021) suggested that cetirizine did not act by a PAF receptor-blocking activity.

Cetirizine is a new anti-allergic compound with a potent, long-acting, and specific antihistaminic property. Strongly active in the therapy of urticaria and seasonal or perennial rhinitis, it has been shown to inhibit the in vivo eosinophil attraction at skin sites challenged with allergen in atopic patients. In the present work, we confirmed that, at a therapeutical concentration, this molecule had a potent inhibitory action in vitro on eosinophil chemotaxis induced either by N-formyl-Met-Leu-Phe or platelet-activating factor and also on the IgE-dependent stimulation of platelets. These observations appear in favour of a possible role for cetirizine in the modulation of inflammatory cell interactions in allergic processes.