BACKGROUND A new fluroquinolone antibacterial agent, antofloxacin hydrochloride, developed in China, is an 8-NH(2) derivant of levofloxacin. The purpose of the study was to evaluate the pharmacokinetic characteristics of single and multiple oral doses of antofloxacin hydrochloride in Chinese healthy male volunteers. METHODS An open-label, non-randomized, single and multiple dose clinical trial was conducted. In single dose study, 12 subjects took 200 mg antofloxacin hydrochloride. In multiple dose study, 12 subjects took antofloxacin hydrochloride 400 mg once on day 1 and 200 mg once daily from day 2 to day 7. HPLC was used to assay the serum and urinary concentrations of antofloxacin. RESULTS In single dose study, the maximum concentration of drug in serum (C(max)), the time to reach C(max) (T(max)), and the area under the serum concentration-time curve (AUC (0-∞)) of antofloxacin were (1.89 ± 0.65) mg/L, (1.29 ± 0.26) hours, and (25.24 ± 7.26) mg×h(-1)×L(-1), respectively. Accumulating elimination rate of antoflocaxin from urine within 120 hours was 39.1%. In multiple dose study, blood concentration of antofloxiacin achieved stable state on day 2 after dosing. The minimum concentration drug in serum (C(min)), AUCss, mean concentration of drug in serum (C(av)), and degree of fluctuation (DF) were (0.73 ± 0.18) mg/L, (47.59 ± 7.85) mg×h(-1)×L(-1), (1.98 ± 0.33) mg/L, and 1.74 ± 0.60, respectively. On day 7 after dosing, T(max), C(max), and AUC (0-∞) was (1.14 ± 0.50) hours, (2.52 ± 0.38) mg/L, and (48.77 ± 8.44) mg×h(-1)×L(-1), respectively. Accumulating elimination rate of antofloxaxin from urine within 120 hours after the last dosing was 60.06%. CONCLUSIONS The regimen of 400 mg loading dose given on the first treatment day and then 200 mg dose once daily results in satisfactory serum drug concentration.