Trimipramine N-oxide is an active metabolite of the tricyclic antidepressant trimipramine .1 It is formed via N-oxidation of trimipramine by the cytochrome P450 (CYP) isoforms CYP2D6, CYP2C9, CYP2C19, CYP1A2, and CYP3A4. Trimipramine N-oxide selectively inhibits the serotonin transporter (SERT) over organic cation transporter 1 (OCT1) and OCT2, the dopamine transporter (DAT), and the norepinephrine transporter (NET) in HEK293 cells expressing the human transporters (IC50s = 3.59, 9.35, 27.4, 9.4, and 11.7 µM, respectively).
1.Haenisch, B., Hiemke, C., and BÖnisch, H.Inhibitory potencies of trimipramine and its main metabolites at human monoamine and organic cation transportersPsychopharmacology (Berl)217(2)289-295(2011)