A double-blind, single-dose, crossover comparison of cetirizine, terfenadine, loratadine, astemizole, and chlorpheniramine versus placebo: suppressive effects on histamine-induced wheals and flares during 24 hours in normal subjects.

Abstract

We objectively tested the relative antihistaminic effects of cetirizine, 10 mg; terfenadine, 120 mg; terfenadine, 60 mg; loratadine, 10 mg; astemizole, 10 mg; chlorpheniramine, 4 mg; and placebo in healthy, male volunteers, mean age 25 +/- 4 years, and mean weight, 73 +/- 9 kg. The wheal areas and flare areas produced by epicutaneous tests with histamine phosphate, 1 mg/ml, before ingestion of the H1-receptor antagonist or placebo, and afterward, at 0.3 and 0.7 hours, then hourly from 1 to 12 hours and at 24 hours, were traced at 10 minutes and measured with an IBM-PC digitizer and stereometric software. In this experimental model, the H1-receptor antagonists differed significantly with regard to time of onset of action, amount of suppression of the histamine-induced wheal and flare, and duration of action. The rank order was, from most effective to least effective, cetirizine, 10 mg; terfenadine, 120 mg; terfenadine, 60 mg; loratadine, 10 mg; astemizole, 10 mg; chlorpheniramine, 4 mg; and placebo.