Comparative efficacy of wheal-and-flare suppression among various non-sedating antihistamines and the pharmacologic insights to their efficacy.
OBJECTIVE
Non-sedating antihistamines (loratadine, fexofenadine, and cetirizine) have been widely used in Thailand. This study examined the time-of-onset and compared the 95% inhibitory effect of these agents on histamine-induced cutaneous reaction so as to understand the diversity of their efficacy.


METHODS
Thirty-one atopic patients were randomized into 4 treatment groups, placebo (n = 7), loratadine (n = 8), fexofenadine (n = 8), and cetirizine (n = 8). They were pricked with histamine every 30 min for 4 hrs. The percentage change of the wheal/flare area was calculated.


RESULTS
All active treatments showed wheal suppression superior to placebo after 210 min for loratadine (P = 0.04); 90 min for fexofenadine (P = 0.009); and 60 min for cetirizine (P = 0.02), while flare suppression was significantly marked after 150 min (P = 0.0008) for loratadine; 90 min for fexofenadine (P = 0.0001), and 60 min for cetirizine (P = 0.006). All drugs except loratadine demonstrated a 95% suppression of wheal superior to the placebo (P = 0.001 for fexofenadine; P = 0.0001 for cetirizine). Only fexofenadine exhibited a 95% suppression of flare statistically superior to placebo (P = 0.02). Discrepancies among the effects of these 3 antihistamines were also detected.


CONCLUSIONS
All antihistamines tested repressed the wheal-and-flare area superbly over the placebo within 4 hours. Cetirizine exerted the fastest onset, and it also appeared to be the most efficacious inhibitor. The heterogeneity of their efficacy probably stems from their diverse physicochemical properties, which have also been discussed.
Roongapinun
Sukit
S
Department of Pharmacology, Faculty of Medicine, Chiang Mai University, Thailand.
Wajajamreon
Somphong
S
Fooanant
Supranee
S
D000293:Adolescent; D000328:Adult; D017332:Cetirizine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D005260:Female; D039563:Histamine H1 Antagonists, Non-Sedating / Q000493:pharmacokinetics / Q000627:therapeutic use*; D006801:Humans; D017336:Loratadine / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D016593:Terfenadine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use*; D014581:Urticaria / Q000188:drug therapy*
D039563:Histamine H1 Antagonists, Non-Sedating; D017336:Loratadine; D016593:Terfenadine; C093230:fexofenadine; D017332:Cetirizine