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Peripheral H1-blockade effect of fexofenadine
1Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Background:
Studies of the suppressive effect of H1-receptor antagonists on the histamine-induced wheal and flare are useful for assessing peripheral H1-blockade.
Objective:
To compare the peripheral H1-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 24 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 H1-blockade studies are useful for investigation of the differences among H1-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 H1-receptor antagonist.