Relative potency of fexofenadine HCl 180 mg, loratadine 10 mg, and placebo using a skin test model of wheal-and-flare suppression.
BACKGROUND
H1-receptor antagonists differ in their ability to produce peripheral H1-blockade. Suppression of histamine-induced flares and wheals is a useful objective test for measuring these differences.


OBJECTIVE
To evaluate the relative potency of fexofenadine HCI 180 mg, loratadine 10 mg, and placebo (PBO) in suppressing histamine-induced flares and wheals and compare the onset, duration, and maximum suppression of histamine achieved with each agent.


METHODS
Thirty healthy volunteers were enrolled in this randomized, double-blind, single-dose, crossover study. Flares and wheals induced by skin-prick testing with histamine 1.8 mg/mL were measured before treatment, every 20 minutes during the first hour after dosing, and thereafter hourly between 2 and 12 hours and between 23 and 25 hours postdose.


RESULTS
Fexofenadine was significantly more effective than loratadine in suppressing the histamine-induced flare response at hours 2 through 7 and 10 through 12 and produced greater flare suppression than did PBO at hours 2 through 25. Onset of flare suppression occurred 2 hours after dosing with fexofenadine and 4 hours after dosing with loratadine. Likewise, fexofenadine was superior to loratadine in suppressing the wheal response from hours 1 through 12 and was more effective than PBO at hours 1 through 12, 24, and 25. Throughout the 25-hour measurement interval, the magnitude of difference in both wheal and flare suppression consistently favored fexofenadine over loratadine.


CONCLUSIONS
In a skin test model of wheal-and-flare suppression, fexofenadine showed rapid distribution into the skin compartment with faster onset of action and greater potency vs loratadine.
Kaliner
Michael A
MA
The Institute for Asthma and Allergy, Chevy Chase, Maryland 20815, USA. Makaliner@aol.com
White
Martha V
MV
Economides
Athena
A
Crisalida
Tera
T
Hale
Mary
M
Liao
Yuning
Y
Christian
Claire D
CD
Georges
George C
GC
Woodworth
Thomas H
TH
Meeves
Suzanne G
SG
D000293:Adolescent; D000328:Adult; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004341:Drug Evaluation; D005260:Female; D006634:Histamine H1 Antagonists / Q000008:administration & dosage*; D006636:Histamine Release / Q000187:drug effects; D006801:Humans; D017336:Loratadine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012882:Skin Tests; D016593:Terfenadine / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D013997:Time Factors; D016896:Treatment Outcome
D006634:Histamine H1 Antagonists; D017336:Loratadine; D016593:Terfenadine; C093230:fexofenadine