ChEBI: Azure B is an organic chloride salt having 3-(dimethylamino)-7-(methylamino)phenothiazin-5-ium as the counterion. It is used in making azure eosin stains for blood smear staining and is an active metabolite of methylene blue. It has a role as a histological dye, a fluorochrome, a drug metabolite, an EC 3.1.1.8 (cholinesterase) inhibitor, an EC 1.4.3.4 (monoamine oxidase) inhibitor, a cardioprotective agent and an antidepressant. It contains a 3-(dimethylamino)-7-(methylamino)phenothiazin-5-ium.