Pharmacokinetics of ertapenem in healthy young volunteers

Ertapenem (INVANZ) is a new once-a-day parenteral P-lactam antimicrobial shown to be effective as a single agent for treatment of various community-acquired and mixed infections. The single- and multiple-dose pharmacokinetics of ertapenem at doses up to 3 g were examined in healthy young men and women volunteers. Plasma and urine samples collected were analyzed using reversed-phase high-performance liquid chromatography with UV detection. Ertapenem is highly bound to plasma protein. The protein binding changes from similar to95% bound at concentrations of <50 mug/ml to similar to92% bound at concentrations of 150 mug/ml (concentration at the end of a 30-min infusion following the 1-g dose). The nonlinear protein binding of ertapenem resulted in a slightly less than dose proportional increase in the area under the curve from 0 h to infinity (AUC(0-infinity)) of total ertapenem. The single-dose AUC(0-infinity) of unbound ertapenem was nearly dose proportional over the dose range of 0.5 to 2 g. The mean concentration of ertapenem in plasma ranged from similar to145 to 175 mug/ml at the end of a 30-min infusion, from similar to30 to 34 mug/ml at 6 h, and from similar to9 to 11 mug/ml at 12 h. The mean plasma t(1/2) ranged from 3.8 to 4.4 h. About 45% of the plasma clearance (CLP) was via renal clearance. The remainder of the CLP was primarily via the formation of the beta-lactam ring-opened metabolite that was excreted in urine. There were no clinically significant differences between the pharmacokinetics of ertapenem in men and women. Ertapenem does not accumulate after multiple once-daily dosing.