Urticaria: clinical efficacy of cetirizine in comparison with hydroxyzine and placebo.

Chronic urticaria is a problem for both physician and patient. In an effort to avoid the risks associated with corticosteroid treatment, many first-generation H1-receptor antagonists have been tried and found to induce undesirable levels of sedation when given in amounts sufficient to control urticaria. Cetirizine, a pharmacologically active oxidized metabolite of hydroxyzine, was developed to provide selective H1-receptor inhibition without depression of the central nervous system. In a 4-week, multicenter, double-blind, placebo-controlled safety and efficacy study, cetirizine, in a once-a-day dose (5 to 20 mg), was equivalent in efficacy to hydroxyzine in divided doses (25 to 75 mg/day). The incidence of somnolence in the cetirizine group was not significantly different from that of the placebo group. However, in the hydroxyzine group, the incidence of somnolence was significantly higher than that in the placebo group (p = 0.001). The results of this study demonstrate that cetirizine has a greater safety margin over the older parent drug hydroxyzine.