CETIRIZINE INHIBITS THE IN-VITRO AND EX-VIVO CHEMOTACTIC RESPONSE OF T-LYMPHOCYTES AND MONOCYTES

We have studied the effect of a nonsedating antihistamine, cetirizine dihydrochloride, on the in vitro chemotaxis of leukocytes from human p eripheral blood. We observed that 0.25 mu g/ml of cetirizine dihydroch loride in vitro significantly inhibited the chemotaxis of monocytes to ward N-formyl-methionyl-leucyl-phenylalanine and leukotriene B-4. High er concentrations of cetirizine, 1.0 and 2.5 mu g/ml, completely inhib ited monocyte chemotaxis without affecting cell viability. T-lymphocyt e migration was also significantly depressed but not abolished. Pyrila mine (mepyramine) was nor inhibitory in equimolar concentrations. Acco rding to these in vitro observations, we extended our studies to measu re monocyte and T-lymphocyte. chemotaxis in an open study, where foul healthy volunteers and six patients with atopic dermatitis took 10 and 20 mg/day cetirizine 3 days. We observed a reduction in ex vivo monoc yte and T-lymphocyte chemotaxis toward N-formyl-methionyl-leucyl-pheny lalanine and leukotriene B-4 without a reduction of the blood cell cou nt. The results were confirmed in an ensuing double-blind, placebo-con trolled study of 16 healthy subjects and 14 adult patients with atopic dermatitis, where ex vivo monocyte chemotaxis was reduced or abolishe d during cetirizine therapy. Serum levels of the two eosinophil-derive d granule proteins, eosinophilcationic protein P and eosinophil protei n X, were not changed during the treatment I period of 7 days. The res ults show that cetirizine dihydrochloride has an inhibitory effect on monocytes and T lymphocytes in vitro and ex vivo. Our findings support the clinical observations that cetirizine dihydrochloride has an anti inflammatory effect besides its H-1-blocking activity.