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 peripheral blood. We observed that 0.25 mu g/ml of cetirizine dihydrochloride in vitro significantly inhibited the chemotaxis of monocytes toward N-formyl-methionyl-leucyl-phenylalanine and leukotriene B-4. Higher concentrations of cetirizine, 1.0 and 2.5 mu g/ml, completely inhibited monocyte chemotaxis without affecting cell viability. T-lymphocyte migration was also significantly depressed but not abolished. Pyrilamine (mepyramine) was nor inhibitory in equimolar concentrations. According to these in vitro observations, we extended our studies to measure 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 monocyte and T-lymphocyte chemotaxis toward N-formyl-methionyl-leucyl-phenylalanine and leukotriene B-4 without a reduction of the blood cell count. The results were confirmed in an ensuing double-blind, placebo-controlled study of 16 healthy subjects and 14 adult patients with atopic dermatitis, where ex vivo monocyte chemotaxis was reduced or abolished during cetirizine therapy. Serum levels of the two eosinophil-derived granule proteins, eosinophilcationic protein P and eosinophil protein X, were not changed during the treatment I period of 7 days. The results 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 antiinflammatory effect besides its H-1-blocking activity.