1,4-Bis(3-(2-(trifluoromethyl)-10H-phenothiazin-10-yl)propyl)piperazine-d8 is labelled 1,4-Bis(3-(2-(trifluoromethyl)-10H-phenothiazin-10-yl)propyl)piperazine (B586705), an impurity of Fluphenazine Decanoate (F598350) which is used in psychotropic drug treatments like those relating to schizophrenia.