Inhibition of histamine-induced nasal obstruction by cetirizine in allergic rhinitis.

This double-blind randomized crossover placebo-controlled study was designed to assess objectively the nasal antihistamine effect of cetirizine in patients with allergic rhinitis and control subjects. Nasal challenge was performed by nebulization of increasing doubling doses of histamine (0; 0.04 to 1.28 mg/nostril) in six patients with allergic rhinitis and six control subjects on cetirizine (2 x 10 mg daily for 3 days) or placebo. Sneezings were counted and nasal obstruction was assessed by subjective scoring and by objective measurement of nasal airway resistance by posterior rhinomanometry. Histamine induced sneezing and a dose-dependent increase in nasal airway resistance and in perceived sensation of obstruction. Responses were greater in patients with allergic rhinitis compared with controls, although of borderline significance for nasal obstruction. Cetirizine totally abolished sneezing and significantly reduced increase in nasal airway resistance and perceived sensation of nasal obstruction both in normal and rhinitic subjects. Our results demonstrate by an objective measurement the nasal antihistamine effect of cetirizine. We propose this simple provocation test to assess the time-course of the effect of antihistamines and to compare the relative potency of related compounds.