In addition, detailed investigation into the relationship between PD values achieved by levofloxacin in patients with acute exacerbations of chronic bronchitis (AECB) and bacterial eradication rates have shown that these PK/PD values can be used as predictors of outcome (2). Clinical and microbiological assessments were performed following administration of levofloxacin 500 mg once daily for 7 days. Results confirmed that while initial serum levels were higher than those of sputum, by 4 hours after administration levels were either equivalent or higher in sputum, reflecting the excellent respiratory penetration of this agent (Figure 1) (2). Treatment was successful in 90% of patients when the area under the plasma concentration-time curve (AUC) from 0 to 24 hours (AUC_0-24)/minimum inhibitory concentration (MIC) ratio was > 125 for serum and > 100 for sputum, and when the maximum serum drug concentration (C_max)/MIC was > 10.01 for serum and > 8.01 for sputum following the first dose (2). This PK/PD target attainment can be easy reach with the current scenario of levofloxacin susceptibility of respiratory pathogens, including Streptococcus pneumoniae (S. pneumoniae ) or Haemophilus influenzae (H. influenzae ).