Effects of loratadine and terfenadine on the induced nasal allergic reaction

To evaluate the effect of terfenadine and loratadine on the early nasal allergic response to challenge and the subsequent cellular influx and hyperresponsiveness.

Double-blind, placebo-controlled, triple-crossover study.

Fourteen, asymptomatic, allergic volunteers.

After an initial challenge with methacholine chloride, subjects received treatment with placebo, loratadine (10 mg by mouth daily), or terfenadine (60 mg by mouth twice daily) for 1 week, followed by a nasal allergen challenge with lavages; 24 hours later, while the subjects were still receiving medication, the quantity of cells in the nasal lavage was determined, and another challenge with methacholine was done. Mediator levels were quantified in the nasal lavages after the allergen c hallenge, and the weight of the methacholine-induced nasal secretions was measured.

Both loratadine and terfenadine treatment resulted in significant reductions in allergen-induced sneezing and the levels of histamine, kinins, albumin, and N-alpha-tosyl-L-arginine methyl ester-esterase activity in recovered nasal lavages compared with the reductions that resulted from placebo treatment, with no significant difference among the treatments. Treatment had no effect on the levels of tryptase, prostaglandin D2 or leukotriene C4. A significant eosinophil influx into nasal secretions 24 hours after the allergen challenge in patients who were receiving placebo (P=.006) was not affected by loratidine or terfenadine treatment. Comparing methacholine-induced secretions between screening challenges and challenges with the patients who were being treated with either loratadine or terfenadine, there was a significant decrease in secretions after the use of these antihistamines (P<.05).

Both loratadine and terfenadine partially inhibit the early nasal response to allergen challenge and the subsequent reactivity to a challenge with methacholine without affecting the influx of eosinophils into nasal secretions.