4-Aminobenzamidine-d4 Dihydrochloride is primarily used in biochemical research as a protease inhibitor. It is particularly effective in inhibiting serine proteases such as trypsin, thrombin, and plasmin, making it valuable in studies involving enzyme kinetics and protein interactions. Its deuterated form allows for use in mass spectrometry and NMR studies, where it serves as an internal standard or labeling agent to enhance the accuracy of analytical measurements. This compound is also utilized in the development of diagnostic assays and in the investigation of blood coagulation pathways, providing insights into therapeutic targets for clotting disorders. Additionally, it finds application in the study of cellular processes where serine proteases play a critical role, aiding in the understanding of disease mechanisms and drug development.