Used as a stable isotope-labeled internal standard in mass spectrometry-based bioanalytical assays for quantification of fluoroquinolone antibiotics in biological matrices. Its deuterated ethyl group provides a distinct mass difference from the non-labeled compound, enabling accurate measurement with minimal interference. Commonly applied in pharmacokinetic and metabolism studies to track drug concentrations in plasma, urine, and tissues. The fluorine and methylpiperazine substituents maintain similar physicochemical properties to the parent drug, ensuring comparable extraction and ionization behavior.