Used primarily as a stable isotope-labeled internal standard in mass spectrometry-based bioanalytical studies. Enables accurate quantification of memantine in biological matrices such as plasma, serum, and brain tissue. Supports pharmacokinetic and metabolism research by allowing differentiation between endogenous memantine and administered drug. Also applied in studies investigating NMDA receptor activity and neuroprotective mechanisms, particularly in models of neurodegenerative diseases like Alzheimer's. Its deuterated structure ensures minimal metabolic conversion, enhancing measurement precision.