(2S)-2-Methyl-2,3,4,5-tetrahydro-1H-3-benzazepine-d3 is the isotope labelled analog of (2S)-2-Methyl-2,3,4,5-tetrahydro-1H-3-benzazepine. (2S)-2-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine is an impurity of Lorcaserine (L469890), which is a novel selective 5-HT2C-receptor agonist for the treatment of obesity.