Comparative study of cetirizine and terfenadine versus placebo in the symptomatic management of seasonal allergic rhinitis

Background: Cetirizine is a new antihistamine with greater selectivity for the histamine H-1 receptor and a low rate of hepatic metabolism. Cetirizine once daily is effective in the symptomatic treatment of seasonal and perennial allergic rhinitis and chronic idiopathic urticaria. Objective: The efficacy and safety of cetirizine 10 mg qd, terfenadine 60 mg bid, and placebo were compared in patients with seasonal allergic rhinitis. Methods: A multicenter, prospective, double-blind, randomized, parallel study was conducted for 2 weeks during the ragweed pollen season in patients with documented allergic rhinitis. Total symptom complex and total symptom complex plus nasal congestion scores, global efficacy, overall satisfaction, and adverse events were assessed at baseline and after 1 and 2 weeks of treatment. Results: Of the 311 patients randomized to treatment, 283 completed the study. Cetirizine produced a marked improvement in symptoms scores compared with placebo after 1 week of therapy (P = .001). By the end of week 1, total symptom complex scores were improved by 37% with cetirizine compared with 29% for terfenadine, and 23% for placebo. An overall treatment effect was evident at week 1 (P = .0019), with marked differences between cetirizine and both placebo (P = .0004) and terfenadine (P = .0464) but not between terfenadine and placebo (P = .1215). A more marked treatment effect was evident during the first week of the study; this appeared to be related to spontaneous resolution of symptoms, since mean pollen counts derived for each patient declined significantly each week of the study. Therapy was generally well tolerated. Headache was the most common side effect in each group. Four patients on cetirizine, one on terfenadine, and two on placebo withdrew because of side effects. Somnolence was reported in 12 patients on cetirizine (P < .05), 2 on terfenadine, and 3 on placebo. Conclusion: Cetirizine produced a greater improvement in symptoms of seasonal allergic rhinitis than terfenadine or placebo.