Pharmacokinetic studies of imipenem/cilastatin in elderly patients

Six patients, aged between 68 and 83 years, with glomerular filtration rates (GFR) between 31 and 80 ml/min received imipenem/cilastatin as treatment for acute lower respiratory tract infection. A combination of 500 mg of both agents was administered, 6-hourly, intravenously over 30 min. After a minimum of four doses, blood specimens were obtained for assay of imipenem and cilastatin concentrations by HPLC. Pharmacokinetic parameters were calculated from the results. The mean half life was 1.6 h for imipenem and 2.1 h for cilastatin, values similar to those reported for patients with moderate renal impairment. Elimination constant, clearance and AUC significantly correlated with GFR but not with age. No accumulation was observed.