Plasma pharmacokinetics and urine concentrations of meropenem in ewes.

The pharmacokinetics of meropenem was studied in five ewes after single i.v. and i.m. dose of 20 mg/kg bw. Meropenem concentrations in plasma and urine were determined using microbiological assay method. A two-compartment open model was best described the decrease of meropenem concentration in plasma after an i.v. injection. The drug was rapidly eliminated with a half-life of elimination (t1/2beta) of 0.39 +/- 0.30 h. Meropenem showed a small steady-state volume of distribution [Vd(ss)] 0.055 +/- 0.09 L/kg. Following i.m. injection, meropenem was rapidly absorbed with a t1/2ab of 0.25 +/- 0.04 h. The peak plasma concentration (Cmax) was 48.79 +/- 8.83 microg/mL was attained after 0.57 +/- 0.13 h (tmax). The elimination half-life (t1/2el) of meropenem was 0.71 +/- 0.12 h and the mean residence time (MRT) was 1.38 +/- 0.26 h. The systemic bioavailability (F) after i.m. injection was 112.67 +/- 10.13%. In vitro protein-binding percentage of meropenem in ewe's plasma was 42.80%. The mean urinary recoveries of meropenem over 24 h were 83% and 91% of the administered dose after i.v. and i.m. injections respectively. Thus, meropenem is likely to be efficacious in the eradication of many urinary tract pathogens in sheep.