Objective        To investigate the pharmacokinetics of levofloxacin in Chinese healthy subjects after single and multiple oral doses of levofloxacin for guiding rational clinical regimen in patients with infectious diseases.       Methods       The drug concentrations in the plasma and urine were assayed by high performance liquid chromatography (HPLC) and the pharma

cokinetic parameters were calculated after a single oral dose of 200

500 or 700 mg levofloxacin to 9 healthy subjects for each dose group

and after multiple doses of 500 mg daily for 7 consecutive days in 9 subjects.       Results       After single dose administration of 200

500 and 700 mg levofloxacin

the peak concentration (C

max

) of levofloxacin in the plasma were 2.43±0.63

7.03±2.47 and 8.96±1.95 mg/L respectively

the area under the concentration-time curve (AUC

0-∞

) were 17.07±1.52

54.76±8.74 and 85.54±9.12 mg·h/L respectively

the values of T

1/2β

were all longer than 7 h

and the doses being excreted in the urine within 72 h for each dose group accounted for over 80%. After multiple doses of levofloxacin administration to the subjects

the values of C

max

C

24h

AUC

0-24h

ratio of day 7 over day 1 was 1.041 5

1.031 4 and 1.126 3 respectively. The parameters related to drug absorption and distribution did not show obvious increase after 7 days’ multiple dose administration to all the subjects. No accumulation was observed after multiple doses administration. About 85.65% of the doses were excreted in the urine within 24 h in day 7. The regimen of 500 mg levofloxacin once daily reached the pharmacokinetic/pharmacodynamic (PK/PD) target for Streptococcus pneumoniae.       Conclusion       Levofloxacin is absorbed rapidly in healthy subjects after oral administration and mainly eliminated from the kidney. No accumulation is observed after multiple dose administration. All the adverse events are mild and well tolerated. The results of PK/PD study indicate the regimen of 500 mg once a day might acquire ideal clinical and microbiological effect in patients with lower respiratory tract infection caused by  Streptococcus pneumoniae.