The effects of olopatadine hydrochloride on the number of scratching induced by repeated application of oxazolone in mice

It is suggested that atopic dermatitis is a skin disease associated with itching as subjective symptoms, and histamine H1 receptor antagonists are used in order to prevent the itching, and the deterioration for scratch by itching. Histamine H1 receptor selective anti-histamine olopatadine hydrochloride (olopatadine; Allelock®) shows consistent efficacy and safety in the treatment of allergic disorders. We investigated the possible efficacy of olopatadine on the number of scratching induced by repeated application of oxazolone in BALB/c mice. The repeated treatment of olopatadine significantly inhibited the ear swelling and the increased number of scratching. It significantly inhibited the increased production of interleukin (IL)-4, IL-1β and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the lesioned ear. Moreover, it significantly inhibited the increased production of nerve growth factor (NGF) and substance P. On the other hand, loratadine, bepotastine and chlorpheniramine did not inhibit the ear swelling and the increased number of scratching. These results indicate that olopatadine inhibited not only the increased production of cytokines but also NGF and substance P unlike other histamine H1 receptor antagonists. It was suggested that olopatadine suppressed the increased number of scratching by the anti-inflammatory effects. Therefore, olopatadine appears to exert additional biological effects besides its blockade of a histamine H1 receptor.