Used as a stable isotope-labeled internal standard in mass spectrometry-based bioanalytical assays for the quantification of perazine in biological matrices such as plasma, serum, or urine. Its primary application is in pharmacokinetic and metabolism studies, where it helps ensure accurate measurement of perazine levels by compensating for matrix effects and instrument variability. Due to its deuterated structure, it closely mimics the chemical behavior of non-labeled perazine while being distinguishable by mass detection, enabling precise and reliable analytical results in drug development and clinical research.