Background: H1-receptor antagonists are effective for the treatment of seasonal allergic rhinitis. In rare circumstances, some second-generation H1-receptor antagonists have been associated with prolongation of the corrected QT interval (QTc), thus increasing the risk of ventricular arrhythmias. Fexofendine HCl, the carboxylic acid metabolite of terfenadine, is a new second-generation antihistamine that is nonsedating and does not cause electrocardiographic effects.
Objective: To investigate the clinical efficacy and safety of fexofenadine HCl in the treatment of ragweed seasonal allergic rhinitis and to characterize the dose-response relationship of fexofenadine HCl at dosages of 60, 120, and 240 mg bid.
Methods: A multicenter, 14-day, placebo-controlled, double-blind trial was conducted with patients suffering from moderate to severe ragweed seasonal allergic rhinitis who met symptom severity criteria after a 3-day placebo baseline period. Patients with minimal or very severe symptoms during the baseline period were excluded. Patients were randomized to receive fexofenadine HCl (60, 120, or 240 mg bid) or placebo at 12-hour dosing intervals (7:00 AM and 7:00 PM). The primary efficacy measure was patient-assessed 12-hour reflective total symptom score before the evening dose (trough).
Results: Five hundred seventy patients completed the trial. Fexofenadine HCl at each dosage provided significant improvement in total symptom score (P < or = .003) and in all individual nasal symptoms compared with placebo. The frequency of adverse events was similar among fexofenadine HCl and placebo groups, with no dose-related trends. No sedative effects or electrocardiographic abnormalities, including prolongations in QTc were detected.
Conclusions: Fexofenadine HCl is both effective and safe for the treatment of ragweed seasonal allergic rhinitis. Because there was no additional efficacy at higher dosages, 60 mg bid appears to be the optimal therapeutic dosage for these patients.