dacemazine dacemazine dacemazine (inn, also known as ahistan and histantine) is a phenothiazine derivative which acts as a histamine antagonist at the h1 subtype. first described in 1951, it was never marketed as a drug on its own, although a combination of dacemazine and di-tert-butylnaphthalenesulfonate was sold as an antispasmodic and antitussive under the trade name codopectyl. it was also assessed as a possible anticancer drug. dacemazineclinical dataatc codenoneidentifiers iupac name 2-dimethylamino-1-phenothiazin-10-ylethanone cas number518-61-6 npubchem cid68846chemspider62079 yunii88d34uy0qichemblchembl2107547 ncomptox dashboard (epa)dtxsid70199733 chemical and physical dataformulac16h16n2osmolar mass284.38 g·mol−13d model (jsmol)interactive image smiles o=c(n1c3c(sc2c1cccc2)cccc3)cn(c)c inchi inchi=1s/c16h16n2os/c1-17(2)11-16(19)18-12-7-3-5-9-14(12)20-15-10-6-4-8-13(15)18/h3-10h,11h2,1-2h3 ykey:hkucyahwpvlpfn-uhfffaoysa-n y ny (what is this?) (verify) synthesis synthesis: patent (ex 8): amide formation between phenothiazine (1) and chloroacetyl chloride (2) gives 10-(chloroacetyl)-phenothiazine (3). the subsequent displacement of the remaining halogen with dimethylamine (4) completes the synthesis of dacemazine (5).