Used as a stable isotope-labeled internal standard in quantitative bioanalytical studies, particularly in mass spectrometry-based assays. Enables accurate measurement of lamotrigine levels in biological matrices such as plasma, serum, or urine by compensating for matrix effects and instrument variability. Commonly applied in pharmacokinetic studies, therapeutic drug monitoring, and metabolism research to ensure precision and reliability of analytical results. Its isotopic distinction from unlabeled lamotrigine allows clear differentiation during detection while maintaining nearly identical chemical and chromatographic behavior.