Limited data exist comparing the peripheral H₁-receptor antagonist activities of the newer-generation antihistamines, fexofenadine and desloratadine.

In a randomized, placebo-controlled, double-blind, crossover histamine-induced wheal and flare study, non-allergic subjects received fexofenadine HCl 180 mg, desloratadine 5 mg or placebo. Histamine (1.8 mg/mL) skin pricks were performed pre-dose, 20, 40 and 60 minutes post-dose, hourly until 12 hours and at 23 and 24 hours. Primary endpoint: difference between baseline and post-dose flare measurements. Secondary endpoints: onset and time to maximum percent suppression. Onset of suppression was the first time a difference in flare (≥5 mm) or wheal (≥1 mm) diameter occurred between antihistamine and placebo from baseline on two consecutive measurements.

Fexofenadine significantly suppressed histamine-induced flares versus placebo from 2–24 hours (p<0.05), and versus desloratadine from 2–6 hours post-dose (p<0.01). Desloratadine significantly suppressed flares versus placebo from 6–10 hours, and at 12 and 24 hours (p<0.05). Onset for flare suppression was 60 minutes for fexofenadine and 5 hours for desloratadine. Fexofenadine significantly suppressed wheals versus desloratadine from 2–4 hours (p<0.001), 6–9 hours (p<0.05), and at 12 hours (p<0.05); onset time was 60 minutes for both antihistamines. For fexofenadine, maximum suppression of flares (84.7%) and wheals (67.8%) occurred at 6 hours. For desloratadine, maximum flare and wheal suppression occurred at 10 hours (51.4%) and 7 hours (30.6%), respectively.

Fexofenadine HCl 180 mg has a faster onset of action at suppressing histamine-induced flare, and provides greater overall flare and wheal suppression than desloratadine 5 mg.