Azelastine eye drops reduce and prevent allergic conjunctival reaction and exert anti-allergic activity

Azelastine is a selective H1-receptor antagonist, which has previously been demonstrated to be effective in the treatment of allergic rhinitis. We have recently demonstrated that nasal azelastine inhibits the clinical and inflammatory events following nasal allergen challenge. Particularly, we focused our attention on ICAM-1 expression on epithelial cells, since it is the natural ligand of LFA-1, an adhesion molecule expressed by leucocytes, including eosinophils.

Since azelastine ocular drops are now available, the aim of the present study was the evaluation of the anti-allergic activity in the model of allergen specific conjunctival challenge (ASCC).

Twenty outpatients with allergic rhinoconjunctivitis due to Parietaria Judaica (Wall Parietary) were included outside the pollen season. The study was designed as randomized, placebo-controlled, double-blind and parallel group, developed in two parts. The former investigated the onset of effect of a single dose of azelastine eye drops administered 20 min after clinical response due to ASCC. The latter evaluated the clinical and inflammatory parameters following ASCC after 7-days treatment with azelastine. Clinical parameters (hyperaemia, itching, lacrimation and eyelid swelling) were evaluated at baseline, 5, 10, 20 and 30 min (i.e. early phase reaction-EPR) and 6 h (i.e. late phase reaction-LPR) after ASCC. Cytological assessment (number of neutrophils, eosinophils. monocytes and lymphocytes) and ICAM-1 expression on conjunctival epithelial cells were evaluated at baseline, 30 min (i.e. early phase reaction-EPR) and 6 h (i.e. late phase reaction-LPR) after ASCC.

When administered 30 min after ASCC, azelastine produced a clinical effect ranging between 10 and 20 min after eye drops administration (P < 0.01). After 7 days of treatment, 30 min after ASCC, azelastine induced a reduction of symptom scores during EPR and LPR (P < 0.01), a reduction of inflammatory cell infiltration during both EPR (P < 0.01) and LPR (P < 0.01), and a reduction of ICAM-1 expression during EPR and LPR (both P < 0.01). Placebo did not modify any of the studied parameters.

Azelastine eye drops exert anti-allergic activity, inducing a rapid improvement of clinical events when administered after ASCC, and reducing both symptoms and cellular infiltration when administered before ASCC. Finally, azelastine down-regulates ICAM-1 expression on epithelial conjunctival cells, confirming the results obtained at nasal level.