Effect of terfenadine on neutrophil and eosinophil chemotactic activities after inhalation of platelet-activating factor in vivo and on neutrophil chemotaxis in vitro

In this double-blind crossover study we evaluated the effect of terfenadine on the rise in neutrophil chemotactic activity (NCA) and eosinophil chemotactic activity (ECA) in serum induced by platelet-activating factor (PAF) inhalation in 8 asthmatics. Additionally, we examined the direct effect of terfenadine on neutrophil chemotaxis in vitro in 7 allergic subjects. NCA and ECA in serum after PAF inhalation and neutrophil chemotaxis were measured using a modified Boyden chamber method. An initial elevation of NCA after PAF inhalation was inhibited by terfenadine, but the effect was diminished after subsequent PAF inhalations. Terfenadine showed no effect on ECA. In vitro PAF- and fMLP-induced neutrophil chemotaxis were significantly inhibited by terfenadine. These results suggest that terfenadine may have antiallergic properties in addition to its H₁ receptor blockade.