Compared peripheral H1 inhibiting effects of cetirizine 2 HCl and loratadine

Histamine-induced wheals and flares were measured in seven healthy volunteers zero, four, and eight hours after oral intake of cetirizine, 2.5, 5, and 10 mg; loratadine, 10, 20, and 40 mg; and placebo. Cetirizine (2.5, 5, and 10 mg) and loratadine (20 and 40 mg) significantly inhibited the histamine-induced wheals at all experimental times and with all histamine concentrations. This was not always the case with loratadine, 10 mg. Cetirizine, 2.5 mg, was as potent in inhibiting the histamine skin reactivity as loratadine, 10 mg.