1-[[2-[(2-Aminophenyl)amino]-5-methyl-3-thienyl]carbonyl]-4-methyl-piperazine-D3 is a labelled analogue of 1-[[2-[(2-Aminophenyl)amino]-5-methyl-3-thienyl]carbonyl]-4-methyl-piperazine (A622452). 1-[[2-[(2-Aminophenyl)amino]-5-methyl-3-thienyl]carbonyl]-4-methyl-piperazine is an impurity of Olanzapine (O253750), a serotonin (5-HT2) and dopamine (D1/D2) receptor antagonist with anticholinergic activity.