Medetomidine-13C-d3 is intended for use as an internal standard for the quantification of medetomidine by GC- or LC-MS. Medetomidine is an imidazole compound that selectively binds to α2-adrenergic receptors (α2-ARs) over α1-ARs (Kis = 1.08 and 1,800 nM, respectively).