Loratadine and terfenadine in perennial allergic rhinitis. Treatment of nonresponders to the one drug with the other drug.

The efficacy of loratadine and terfenadine in perennial allergic rhinitis was evaluated in a double-blind, selected cross-over study consisting of two phases. During the first phase, 76 patients with perennial allergic rhinitis, 8-67 years old, were included in the study. Of these, 41 patients received loratadine 10 mg daily, and 35 patients received terfenadine 60 mg twice daily, for 2 weeks. According to symptoms and side-effects, 32 patients were classified as responders to loratadine, and 28 patients as responders to terfenadine. All observed symptoms were significantly reduced in both treatment groups, but with no significant differences between the two groups. Side-effects were few and mild. In patients with normal IgE, loratadine was significantly superior to terfenadine in relieving nasal secretion, whereas terfenadine was significantly superior to loratadine in relieving nasal congestion. In patients with increased IgE, patients treated with loratadine showed significantly greater reduction in sneezing than patients treated with terfenadine. A positive correlation between total IgE and reduction in overall symptoms was found for patients treated with loratadine, whereas a negative correlation was found for patients treated with terfenadine. During the second study phase, the nonresponders received the other drug for 2 weeks. All seven nonresponders to terfenadine responded to loratadine after crossing over, whereas four of nine nonresponders to loratadine responded to terfenadine. Nonresponders to one drug may respond to the other drug. Thus, more than one antihistamine drug should be tried in perennial allergic rhinitis if the first fails.