OBJECTIVE The aim of this study was to investigate the pharmacokinetics and dose proportionality of a single, intravenous dose of pazufloxacin mesilate, an injectable fluoroquinolone antibiotic, in healthy Korean male volunteers. METHODS In this open-label, four-dose, parallel study, subjects were randomized to receive a single dose of pazufloxacin mesilate 300, 500, 600, and 1,000 mg (n = 6, 20, 6, and 8, respectively) administered as a 1-h intravenous infusion. Blood and urine samples were collected serially from 0 to 24 h after drug administration and analyzed using a validated HPLC method. Tolerability was assessed by monitoring clinical laboratory parameters and adverse events. RESULTS After single-dose intravenous administration of pazufloxacin mesilate, the mean C(max) for groups treated with 300, 500, 600, and 1,000 mg doses ranged from 5.11 to 18.06 μg/mL; the mean AUC(0-t) ranged from 13.70 to 58.60 μg × h/mL. Pazufloxacin exhibits Lack of dose proportionality was concluded over the dose range of 300 - 1,000 mg, based on linear regression model and power model . At all four dosages studied, pazufloxacin mesilate was well tolerated. CONCLUSIONS Our data suggest that all regimens of pazufloxacin administration were well tolerated. Pazufloxacin exhibits lack of dose proportionality over the dose range of 300 - 1,000 mg.