Pharmacokinetics of garenoxacin in elderly patients with respiratory tract infections

The pharmacokinetics of the new oral des-fluoroquinolone antimicrobial garenoxacin (GRNX) was investigated in elderly patients with respiratory tract infections. Patients were treated with GRNX (200mg or 400mg) once daily for 7 days. Plasma GRNX concentrations were determined and pharmacokinetic parameters were estimated by Bayesian predictions using reported population pharmacokinetic parameters. At each dose, the maximum plasma concentration (Cmax) and the area under the concentration–time curve (AUC) were comparable with those reported in young subjects, except that the estimated Cmax and AUC values in one patient receiving the 200mg dose whose body weight and creatinine clearance rate (CLCr) were 38kg and 17mL/min, respectively, were higher than those of the other patients given 200mg GRNX and were comparable with those of patients who received the 400mg dose. These results suggest that the recommended dose of GRNX should be 400mg for most elderly and young patients, but only 200mg in patients whose body weight and CLCr are <40kg and <30mL/min, respectively.