The present invention relates to a non-radioactive, heavy-atom isotopologue of Compound 1 containing one or more deuterium in place of a hydrogen covalently bound to carbon. The Compound 1 isotopologues of the invention are inhibitors of norepinephrine uptake and possess unique biopharmaceutical and pharmacokinetic properties compared to the corresponding non-isotope containing compounds. They may also be used to accurately determine the concentration of Compound 1 in biological fluids. The invention further provides compositions comprising these heavy-atom Compound 1 isotopologue and methods of treating diseases and conditions linked to reduced neurotransmission of norepinephrine.