Background: Azelastine hydrochloride (azelastine) nasal spray is a histamine receptor-1 (H1) antagonist often used in treating allergic rhinitis to relieve its symptoms. However, the effects of azelastine to influence decongestion on human nasal mucosa in patients with allergic rhinitis are not yet fully explored and merit further exploration. The effects of azelastine on the vasocontrac-tile responses generated by smooth muscles in the vascular structures of human nasal mucosa were investigated directly in vitro. Methods: We examined the effectiveness of azelastine on isolated human nasal mucosa by testing: 1) the effect on mucosa resting tension; 2) the effect on mucosal contraction caused by 10-6 M methoxamine as a sympathetic mimetic; 3) the effect of the drugs on electrically induced mucosal contractions. Results: The results indicated that addition of methoxamine to the incubation medium caused the nasal mucosa to contract in a dose-dependent manner. Addition of azelastine at doses of 10–6 M or above elicited a significant dilation response to 10–6 M methoxamine-induced mucosal contraction. Azelastine could inhibit electrical field stimulation-induced spike mucosal contraction. Moreover, increase in concentration of azelastine had minimal effect on basal tension of nasal mucosa. Conclusions: The technique in our study is simple and reproducible. Azelastine could inhibit both EFS and methoxamine-induced nasal mucosal contractions in vitro. This study highlights that although azelastine nasal spray is often used in treating allergic rhinitis to improve symptoms, nasal obstruction may be not relieved immediately due to the anti-sympathetic effect of azelastine.
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