The aim of the present investigation was to examine the effect of a I-week oral administration of the anti-allergic drug cetirizine on healthy volunteer neutrophil chemotaxis and superoxide anion (O-2-) production. Eight male volunteers were selected after clinical examination and laboratory tests. Neutrophils were isolated from peripheral blood using a discontinuous density gradient. Spontaneous migration and platelet activating factor(PAF, 10(-6) and 10(-8) M) or zymosan-activated plasma (ZAP)-induced chemotaxis were studied in a 48-well microchemotaxis chamber. Basal and phorbol 12-myristate 13-acetate (PMA, 30 nM) stimulated O-2- production were measured spectrophotometrically. Cetirizine (10 mg per day) was given orally during 1 week. Both neutrophil chemotaxis and O-2- production were assessed before and 2 h, 24 h, and 1 week after orally administered cetirizine. Plasma cetirizine levels were monitored by high performance liquid chromatography (HPLC) with ultraviolet detection. Spontaneous neutrophil migration and PAF- or ZAP-induced chemotaxis showed no significant variation before or at various intervals after the initiation of treatment with cetirizine. Basal and PMA-stimulated neutrophil O-2- production was also not affected by cetirizine. The maximum concentration attained by cetirizine (C-max) was 293 +/- 38 ng/ml and generally peaked (T-max) within 1.9 +/- 0.7 h. We conclude that the administration of cetirizine for 1 week does not alter human neutrophil chemotaxis and O-2- production.34396100