Pharmacodynamics of levofloxacin in patients with acute exacerbation of chronic bronchitis

Study objectives: Levofloxacin is a fluoroquinolone antimicrobial agent for which pharmacodynamic relationships between the maximum serum antibiotic concentration (Cmax)/minimum inhibitory concentration (MIC) ratio and/or the area under the serum concentration-time curve during a 24-h dosing period (AUC(0-24))/MIC ratio and clinical and/or microbiological outcomes have been developed. In this study, we examined the relationship between the in vitro bacteria] susceptibility to levofloxacin, the achieved levofloxacin serum and sputum concentrations, and the in vivo bacterial eradication in patients with acute exacerbations of chronic bronchitis. Patients and interventions: Thirty patients received levofloxacin, 500 mg/d po for 7 days. Samples of venous blood and sputum for the determination of levofloxacin concentrations were collected on day 1 immediately prior to dosing, and then at 1, 4, 8, 12, and 24 11. Results: The mean peak concentration in serum (6.5 mg/L) was found I h after administration, and at 4 h after administration in sputum (5.1 mg/L). Levofloxacin was always detectable 24 h after administration from both samples. Successful treatment occurred in 90% (27 of 30 patients) when assessed both clinically and bacteriologically. Treatment was successful in eight patients when the AUC(0-24)/MIC ratio was > 40 for serum, and in nine patients when it was > 30 for sputum. Treatment was also successful in seven patients when the Cmax/MIC ratio was > 5.01 for serum, and in nine patients when the Cmax/MIC ratio was > 4.01 for sputum. Treatment was successful in 90% (27 of 30 patients) when the AUC(0-24)/MIC ratio was > 125 for serum and > 100 for sputum, and when Cmax/MIC was > 10.01 for serum and > 8.01 for sputum following the first dose. Conclusions: The pharmacodynamics values that we have obtained in sputum with levofloxacin may be used as predictors of therapy outcomes.