Efficacy of repeated pretreatment with olopatadine hydrochloride on rhinitis induced by intranasal instillation of toluene-2,4-diisocyanate in rats.

It is well known that starting treatment for cedar pollinosis therapy with second-generation antihistamines before the initial day of pollen scattering can relieve nasal symptom severity during the pollen season. Olopatadine hydrochloride (olopatadine) is an antiallergic agent with histamine H(1) receptor antagonistic action. We have evaluated the effects of repeated preadministration of olopatadine on the toluene-2,4-diisocyanate-induced rhinitis in rats. A single administration of olopatadine suppressed sneezing and the increases in histamine, nerve growth factor (NGF) and vascular endothelial growth factor (VEGF) production in nasal lavage fluid. When olopatadine was administered repeatedly once a day for 7 days before provocation, its inhibitory effects were enhanced compared to the effect of a single administration. Although the repeated administration of fexofenadine enhanced the inhibitory effects on sneezing, it did not inhibit the increases in NGF and VEGF production. These results show that the suppression of the increase in NGF and VEGF might partially be involved in the improvement of nasal allergy signs by the treatment with olopatadine. It is expected that the early treatment with olopatadine may achieve stable therapeutic effects.