ObjectiveTo determinate the concentration of isonicotinyl hydrazide (INH) in the hydrothorax and thereby increase the drug concentration of the hydrothorax to enhance the anti-tuberculosis efficacy through experiments. MethodsBetween February and June 2009, we used high performance liquid chromatography (HPLC) to determinate the concentration of INH in the hydrothorax of tuberculosis (TB) patients. The separation of sample was performed on Agilent ZORBAX SB-C18 (5 μm, 4.6 mm×2.5 mm) column with a fixed sample injection volume of 20 μL. The mobile phase was methanol-water (20︰80) at a flow rate of 1 mL/min. The ultraviolet detective wavelength was set at 254 nm; The column temperature was room temperature. ResultsIn the range of 0.25-10.00 μg/mL (r=0.998 9), moxi-floxacin showed a good linear relation in HPLC. The recoveries of moxi-floxacin at three concentrations (0.5, 5.0, and 10.0 μg/mL) were 97.95%, 100.64%, and 102.84%, respectively, with intra-day relative standard deviation (RSD) at 3.49%, 1.45%, and 2.03%, respectively and intra-day RSD at 3.85%, 5.68%, 4.15%, respectively. ConclusionThe measuring method adopted in the experiment can accurately determinate the concentration of INH in the hydrothorax with high sensitivity and exceptional reproducibility.