Used in research and development as a deuterated analog of vortioxetine, a common antidepressant. It serves as an internal standard in analytical chemistry, particularly in mass spectrometry, to ensure accurate quantification of vortioxetine in biological samples. This helps in pharmacokinetic studies, drug metabolism research, and quality control in pharmaceutical manufacturing. Its stable isotopic labeling allows for precise tracking and differentiation from non-labeled compounds in complex matrices.