Onset of action of a topical antihistamine as assessed by histamine challenge-induced plasma exudation responses.

Background: Although usually administered orally, antihistamines are available also for topical use in allergic rhinitis. Information on onset of action of these drugs is incomplete.

Objective: To examine onset of action of topical cetirizine-dinitrate on plasma exudation evoked by repeated nasal histamine challenges.

Methods: A liposome formulation of cetirizine-dinitrate (2.44 mg per nasal cavity) was delivered via a nasal spray device as 2 consecutive actuations per nasal cavity in a placebo-controlled design. The nasal mucosal surface was challenged and lavaged with a histamine solution (100 microg/mL) 5, 15, 25, and 55 minutes after each treatment. In addition, the mucosa was lavaged with saline before each treatment. The lavage fluid levels of alpha2-macroglobulin were measured as an index of mucosal exudation (luminal entry) of plasma.

Results: Histamine produced significant increases in nasal lavage fluid levels of alpha2-macroglobulin at all observation points (5 through 55 minutes after treatment). Nasal cetirizine-dinitrate significantly inhibited this response at 5 and 15 minutes after treatment.

Conclusions: The effect of topical cetirizine-dinitrate, as established by histamine challenge-induced mucosal exudation of plasma, has an early onset (ie, within 5 to 10 minutes).