Oseltamivir-d3 is primarily used in research and development as a deuterated analog of oseltamivir, the active ingredient in the antiviral medication Tamiflu. It serves as an internal standard in analytical studies, particularly in mass spectrometry, to ensure accurate quantification and detection of oseltamivir in biological samples. This application is critical in pharmacokinetic studies, where researchers analyze drug absorption, distribution, metabolism, and excretion in the body. Additionally, Oseltamivir-d3 aids in the development of more precise diagnostic methods and the improvement of therapeutic monitoring for patients undergoing antiviral treatment. Its use helps enhance the reliability of data in clinical and laboratory settings, contributing to advancements in antiviral research.