Tetrabenazine-d6 is intended for use as an internal standard for the quantification of tetrabenazine (Item No. 20380) by GC- or LC-MS. Tetrabenazine is an inhibitor of vesicular monoamine transporter 2 (VMAT2) that is selective over VMAT1 (Kis = 97 and >200 nM, respectively, in a serotonin uptake assay).1 It dose-dependently reduces levels of the monoamines norepinephrine (Item No. 16673), dopamine (Item No. 21992), and serotonin (5-HT; Item No. 14332) in rat brain and has been used to induce depressive-like behavior in animal models.2,3 Tetrabenazine (5 mg/kg) improves performance in balance beam and rotarod tests and prevents decreases in the number of striatal medium spiny neurons (MSNs) in a YAC128 transgenic mouse model of Huntington’s disease.4 Formulations containing tetrabenazine have been used in the treatment of chorea associated with Huntington’s disease.WARNING This product is not for human or veterinary use.