Used as a stable isotope-labeled internal standard in mass spectrometry-based bioanalytical assays. Enables accurate quantification of related pharmaceutical compounds in biological matrices by minimizing matrix effects and correcting for variability in sample preparation and instrument performance. Commonly applied in pharmacokinetic and metabolism studies where high sensitivity and precision are required. Its deuterated structure provides a distinct mass difference from the non-labeled analog, allowing clear differentiation during detection while maintaining nearly identical chemical behavior.