Anastrozole-d12 is primarily used as an internal standard in analytical chemistry for the quantification of Anastrozole in various biological samples. Its deuterated structure ensures minimal interference with the analyte, providing accurate and reliable results in mass spectrometry-based assays. This compound is especially valuable in pharmacokinetic studies, where precise measurement of Anastrozole concentrations in plasma, serum, or tissues is critical. Additionally, it aids in quality control processes during the development and validation of analytical methods, ensuring consistency and reproducibility in research and clinical settings. Its application is crucial in advancing studies related to hormone-dependent cancers, particularly breast cancer, where Anastrozole is a key therapeutic agent.