A phthalazine compound having an oxo substituent at the 1-position, a 1-methylazepan-4-yl group at the 2-position and a 4-chlorobenzyl substituent at the 4-position. ChEBI: Azelastine is a phthalazine compound having an oxo substituent at the 1-position, a 1-methylazepan-4-yl group at the 2-position and a 4-chlorobenzyl substituent at the 4-position. It has a role as a H1-receptor antagonist, an anti-allergic agent, an anti-asthmatic drug, a bronchodilator agent, a platelet aggregation inhibitor and an EC 1.13.11.34 (arachidonate 5-lipoxygenase) inhibitor. It is a member of phthalazines, a tertiary amino compound and a member of monochlorobenzenes.