talastine talastine talastine (trade name ahanon) is an antihistamine. talastineclinical dataatc coder06ab07 (who) identifiers iupac name 4-benzyl-2-phthalazin-1(2h)-one cas number16188-61-7 ypubchem cid65624chemspider59065 yunii49ab2pa48bcomptox dashboard (epa)dtxsid20167265 chemical and physical dataformulac19h21n3omolar mass307.397 g·mol−13d model (jsmol)interactive image smiles o=c1c3ccccc3\c(=n/n1ccn(c)c)cc2ccccc2 inchi inchi=1s/c19h21n3o/c1-21(2)12-13-22-19(23)17-11-7-6-10-16(17)18(20-22)14-15-8-4-3-5-9-15/h3-11h,12-14h2,1-2h3 ykey:lcaamxmulmcklj-uhfffaoysa-n y (verify) synthesis the amide proton from 4-benzylphalazone is abstracted with koh, which is then alkylated with diethylaminoethyl chloride.