Atazanavir-d5 is primarily used as an internal standard in analytical chemistry for the quantification and detection of atazanavir in various biological samples. Its deuterated form ensures accurate and precise measurements in mass spectrometry, minimizing interference from the non-deuterated compound. This application is crucial in pharmacokinetic studies, therapeutic drug monitoring, and research focused on understanding the metabolism and distribution of atazanavir in the body. By providing a stable reference, it aids in ensuring reliable data for clinical and experimental purposes.