Clinical pharmacology of the H-1-receptor antagonists cetirizine and loratadine in children

H-1-receptor antagonists are widely used in children but are not as well-st udied in children as they are in adults. Our objective was to determine the onset and duration of action and the relative potency of the H-1-receptor antagonists cetirizine and loratadine in children. We performed a prospecti ve, randomized, placebo-controlled, double-blind, crossover, single-dose st udy of cetirizine and loratadine using suppression of the histamine-induced wheal and flare as the primary outcome. In 15 allergic children, mean age 9 years, compared with baseline, cetirizine (10 mg) suppressed the wheals a nd flares significantly from 0.25 to 24 h, achieving nearly 100% of flare s uppression from 2 to 24 h, inclusive, and loratadine (10 mg) suppressed the wheals and flares significantly from 0.75 to 24 h, inclusive. Cetirizine s uppressed the wheals and flares significantly more than loratadine from 0.2 5 to 1 h, inclusive, and at 0.5, 1, 2, 3, 5, 6, 7, and 24 h, respectively. Placebo also suppressed the wheal and flare significantly at some assessmen t times. Cetirizine and loratadine both have excellent antihistaminic activ ity in children, with a rapid onset of action and a 24-h duration of action in this population.