OBJECTIVE To study the pharmacokinetics of levofloxacin-methane sulfonic acid (LF-MSA)in 8 patients with pulmonary tuberculosis after administration 400 mg orally.METHODS The concentrations of LF-MSA in serum were measured by HPLC.The pharmacokinetic paramters were obtained using 3P97 program.RESULTS The results showed that a one-compartment model with 1 st order absorption were fitted for LF-MSA.The average values of tmax was 1.22 h.The concentrations of LF-SA in serum was (4.52±0.72) mg*L-1.The mininal concentrations of LF-AS at 24 hr after a single dose was (0.52±0.26) mg*L-1.The average area under the curve was (48.35±5.38) mg*h*L-1.The elimination half-life was (6.49±1.70) h.The apparent volume of distribution was (77.48±8.33)L.CONCLUSION According to our study,it was suggested that 400 mg twice daily may be given in order to maintain the concentrations of LF-SA in serum around 24 hours above the minimal concentrations of bactericide.