Olopatadine ophthalmic solution suppresses substance P release in the conjunctivitis models

Olopatadine hydrochloride ophthalmic solutions are treated for allergic conjunctival diseases that are a selective histamine H1 receptor antagonist and an inhibitor of the release of mediators including histamine from the human mast cells. Substance P (SP) levels are increased in tears of patients with allergic conjunctivitis. However, little is known about the regulation of SP release by anti-allergic ophthalmic solutions.

We investigated that the effect of olopatadine hydrochloride ophthalmic solutions (olopatadine 0.1% and olopatadine 0.2%) on rat conjunctivitis models compared with other anti-allergic ophthalmic solutions.

Conjunctivitis was induced by subconjunctival injection of histamine or intravenous injection of ovalbumin in rats passively sensitized with anti-ovalbumin anti-serum. The releases of SP were determined in the conjunctiva and tears using rat antigen-induced conjunctivitis models.

Olopatadine 0.1% and 0.2% significantly inhibited the increased conjunctival dye leaked in the histamine- or antigen-induced hyperpermeability. The inhibitory effects by olopatadine were more potent than by other tested anti-allergic ophthalmic solutions. Moreover, olopatadine significantly inhibited the release of SP from the conjunctiva.

These results indicate that olopatadine ophthalmic solutions appear to exert additional SP release inhibition besides dual-action such as selective histamine H1 receptor antagonistic action and mast cell stabilization action.