Optimisation of imipenem regimens in patients with impaired renal function by pharmacokinetic-pharmacodynamic target attainment analysis of plasma and urinary concentration data

In this study, a pharmacokinetic-pharmacodynamic (PK-PD) target attainment analysis of imipenem (IPM) in patients with impaired renal function was conducted. IPM (500 mg) was administered via a 0.5-h or 1-h infusion to 27 patients with varying renal function. A population PK model was developed by simultaneously fitting plasma and urinary concentration data. A two-compartment model adequately described IPM pharmacokinetics, and creatinine clearance (CLCr) was identified as the most significant covariate. A PK-PD simulation predicted the probabilities of attaining the target in plasma [40% of the time above the minimum inhibitory concentration (MIC)] and defined the PK-PD breakpoints (the highest MICs at which the probabilities were ≥90%). In a patient with a CLCr of 90 mL/min, prolongation of infusion time (from 0.5 h to 1.5 h) increased the PK-PD breakpoint from 1 μg/mL to 2 μg/mL with a 500 mg dose every 8 h (q8h) and from 2 μg/mL to 4 μg/mL with a 500 mg dose every 6 h (q6h). Meanwhile, in a patient with a CLCr of 20 mL/min, the PK-PD breakpoints for both 0.5-h and 1.5-h infusions were 1 μg/mL with a 250 mg dose every 12 h (q12h), 2 μg/mL with a 250 mg dose q8h and a 500 mg dose q12h, and 4 μg/mL with a 250 mg dose q6h. These results indicate that a shorter dosing interval is beneficial in patients with impaired renal function as it results in greater PK-PD breakpoints and a reduction in excessive maximum plasma concentrations. These results help to optimise IPM regimens, particularly in patients with impaired renal function.