ABSTRACT
Pazufloxacin eardrops are a topical quinolone agent for the treatment of outer ear infection. The present study evaluated the pharmacokinetics and topical distribution of pazufloxacin eardrops by a sensitive LC-MS/MS method for determining pazufloxacin in plasma and otorrhea. Plasma and otorrhea samples were extracted by acetonitrile-induced protein precipitation and were subjected to liquid chromatography-tandem mass spectrometric analysis with an electrospray ionization interface. The samples were separated on an HSS T3 column (50 mm×2.1 mm, 1.8 μm). To avoid the matrix effect, gradient elution was performed with the mobile phase consisting of methanol and 1 mmol·L-1 ammonium acetate aqueous solution (0.1% formic acid). The ion transitions for pazufloxacin and pazufloxacin-d4 were m/z 319.1→281.2 and m/z 323.1→285.2, respectively, under the multiple reaction monitoring (MRM) mode. The method was linear in the range of 0.010 0 - 8.00 ng·mL-1 for pazufloxacin in plasma and 0.500 - 1 000 ng·mg-1 in otorrhea. The intra- and inter-day accuracy and precision for pazufloxacin in plasma and in otorrhea met acceptable criteria. The clinical trial was approved by the Society of Ethics and conducted in Nanjing First Hospital and Jiangsu Province Hospital. The validated methods were used in a systemic and topical pharmacokinetic study of 0.1% pazufloxacin eardrops in 3 patients with chronic suppurative otitis media.