Azelastine- 13 C,d 3 (hydrochloride) is the 13 C- and deuterium labeled Azelastine hydrochloride. Azelastine- 13 C,d 3 (hydrochloride), an antihistamine, is a potent and selective histamine 1 (H1) antagonist. Azelastine- 13 C,d 3 (hydrochloride) can be used for the research of allergic rhinitis, asthma, diabetic hyperlipidemic and SARS-CoV-2.