Peripheral H1-blockade effect of fexofenadine

Background: Studies of the suppressive effect of H-1-receptor antagonists on the histamine-induced wheal and flare are useful for assessing peripheral H-1-blockade. Objective: To compare the peripheral H-1-blockade produced by fexofenadine, 60 mg twice daily or 120 mg once daily; loratadine, 10 mg once daily; and placebo during 24 hours. Methods: In this randomized, double-blind, single-dose, crossover study in 20 subjects, the wheals and flares produced by epicutaneous tests with histamine phosphate 1 mg/mL were measured before and at intervals (20, 40, 60 minutes, hourly until 12 hours, and 24 hours) after the ingestion of fexofenadine, 60 mg twice daily; fexofenadine, 120 mg once daily; loratadine, 10 mg once daily; or placebo. Results: All active medications effectively suppressed the histamine-induced wheal and flare for 23 hours compared with placebo. Fexofenadine 60 mg twice daily and fexofenadine 120 mg once daily had a faster onset of action than loratadine in this experimental model. Conclusions: Peripheral H-1-blockade studies are useful for investigation of the differences among H-1-receptor antagonists. They complement large clinical trials in which efficacy is subjectively assessed using symptom scores, and which are more likely to demonstrate similarities among the different medications in this class, and among different doses of the same H-1-receptor antagonist.