Inhibitory effect of olopatadine hydrochloride on the sneezing response induced by intranasal capsaicin challenge in guinea pigs.

To investigate the possible inhibitory effect of olopatadine hydrochloride (olopatadine), an antiallergic drug, on the tachykinin-mediated nasal responses, we examined the effect of olopatadine on the sneezing and the nasal rubbing responses induced by intranasal capsaicin challenge in guinea pigs. Olopatadine (10 mg/kg, p.o.) inhibited the sneezing response by 57% without affecting the nasal rubbing one. The antihistamines chlorpheniramine and clemastine did not affect the responses. Morphine caused the inhibition of both responses, which was antagonized by naloxone. These results suggest that olopatadine inhibits the sneezing response by the inhibition of the tachykinin release and not by its antihistaminic action.