A simple chromatographic method for determining norfloxacin and enoxacin in pharmacokinetic study assessing CYP1A2 inhibition

• Published in: Biomedical chromatography Vol. 25; no. 4; pp. 435 - 438
• Main Authors: Kobayashi, Toshimi, Homma, Masato, Momo, Kenji, Kobayashi, Daisuke, Kohda, Yukinao
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.04.2011
• Subjects: Adult; blood concentration; Caffeine - pharmacokinetics; Caffeine - urine; Chromatography, High Pressure Liquid - methods; Chromatography, Reverse-Phase; CYP1A2; Cytochrome P-450 CYP1A2; Cytochrome P-450 CYP1A2 Inhibitors; enoxacin; Enoxacin - blood; Enoxacin - pharmacokinetics; Enoxacin - urine; HPLC; Humans; Male; norfloxacin; Norfloxacin - blood; Norfloxacin - pharmacokinetics; Norfloxacin - urine; Reproducibility of Results; Sensitivity and Specificity; Theophylline - pharmacokinetics; Theophylline - urine
• ISSN: 0269-3879; 1099-0801; 1099-0801
• DOI: 10.1002/bmc.1488

We developed a simple assay method for the determination of serum and urine norfloxacin and enoxacin using reversed‐phase high‐performance liquid chromatography and perchloric acid precipitation for sample pre‐treatment. Optimized conditions can permit detection of norfloxacin and enoxacin in the same chromatogram, so either compound can be used as an internal standard for another determinant. Supernatants of the precipitated samples were analyzed by the octadecylsilyl silica‐gel column under ambient temperature and an ultraviolet wavelength of 272 nm. A mobile phase solvent consisting of 20 mm sodium dihydrogenphosphate (pH 3.0) and acetonitrile (85:15, v/v) was pumped at a flow rate of 1.0 mL/min. The calibration curves for norfloxacin and enoxacin at a concentration of 62.5–1000 ng/mL for serum and 250–4000 ng/mL for urine were linear (r > 0.9997). The recoveries of norfloxacin and enoxacin from serum and urine were >94% with the coefficient of variations (CV) <5%. The CVs for intra‐ and inter‐day assay of norfloxacin and enoxacin were <4.2 and <5.5%, respectively. This method can be applied to the pharmacokinetic study of norfloxacin and enoxacin after repeated administration to assess changes in CYP1A2 activity in healthy subjects. Copyright © 2010 John Wiley & Sons, Ltd.