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.