2-[2-[4-(2,3-Dimethylphenyl)-1-piperazinyl]-2-oxoethyl]-4-(4-pyridinylmethyl)-1(2H)-phthalazinone-D8is isotope labelled analog for 2-[2-[4-(2,3-Dimethylphenyl)-1-piperazinyl]-2-oxoethyl]-4-(4-pyridinylmethyl)-1(2H)-phthalazinone. 2-[2-[4-(2,3-Dimethylphenyl)-1-piperazinyl]-2-oxoethyl]-4-(4-pyridinylmethyl)-1(2H)-phthalazinone, is a derivative of 4-[(pyridin-4-yl)methyl]-2H-phthalazin-1-one (P991600) and 1-(2,3-dimethylphenyl)-piperazine (D476960). 1-(2,3-Dimethylphenyl)-piperazine, is used in the biological and analytical studies in identifying low-efficacy partial substrates for biogenic amine transporters.