Atazanavir-d6 is primarily used as an internal standard in analytical chemistry for the quantification of atazanavir in biological samples. It plays a crucial role in pharmacokinetic studies, helping researchers accurately measure the concentration of atazanavir in plasma or serum during drug development and therapeutic monitoring. Its deuterated structure ensures minimal interference with the analyte, providing reliable and precise results in liquid chromatography-mass spectrometry (LC-MS) assays. This application is essential for optimizing dosing regimens and ensuring the efficacy and safety of atazanavir in HIV treatment.