Ayman M. Noreddin

Objective: This study aimed to assess the probability of Levofloxacin (Levo) compared to Gatifloxacin (Gati) achieving favorable pharmacodynamic (PD) targets for bacterial eradication and prevention of resistance development in S. pneumoniae in both elderly (≥65 years) and younger (<65 years) patients with Community Acquired Pneumonia (CAP). Material and Methods: As part of a study comparing the clinical outcome of Levo vs. cefuroxime + erythromycin in hospitalized patients with CAP, demographics including age, weight, gender, race and renal function were gathered and analyzed from 263 elderly (≥65 years) and 48 younger patients (<65 years). Previously described and validated population pharmacokinetic (PK) models of levo and gati in patients with CAP were utilized. Free-drug AUC0-24 (f AUC0-24)were simulated in plasma (P) using Levo dosing at 500 mg, 750 mg and 1000 mg OD as well as Gati 200 mg and 400 mg OD. Use of Monte Carlo simulation allowed for the full variability of encountered drug clearance to be incorporated. S. pneumoniae susceptibility data were obtained from the Canadian Respiratory organism Susceptibility Study (CROSS) study (an annual, national, ongoing surveillance study which has collected 8014 isolates from 1997-2004). Results: Probability of target attainment (f AUC0-24/MIC of 30) of Levo and Gati will be discussed Conclusions: For all patients and for elderly hospitalized patients with CAP, Levo 750mg and Gati 400mg showed high probability for target attainment of f AUC0-24/MICall of 30.