This paper describes the pharmacokinetic profile of
procaine penicillin G after intraperitoneal (IP) administration in eight lactating dairy cows.
Procaine pencillin G (PPG, 21 000 IU/kg) was deposited into the abdominal cavity of each cow following an incision in the right paralumbar fossa. Blood and milk samples were taken over the following 10 days, at which point the cows were euthanized. Plasma, milk, muscle, liver, and kidney
penicillin concentrations were determined by HPLC, with a limit of quantification of 5 ng/mL for plasma and milk and 40 ng/g for tissue samples. A noncompartmental method was used to analyze plasma kinetics. The mean pharmacokinetic parameters (+/-SD) were: C(max), 5.5 +/- 2.6 microg/mL; T(max), 0.75 +/- 0.27 h; AUC(0-infinity), 10.8 +/- 4.9 microg x h/mL; MRT, 2.2 +/- 0.9 h. All milk from treated cows contained detectable
penicillin residues for a minimum of three milkings (31 h) and maximum of five milkings (52 h) after administration. Concentrations of
penicillin in all muscle, liver, and kidney samples taken 10 days postadministration were below the limit of quantification. Necropsy examinations revealed foci of
hemorrhage on the rumenal omentum of most cows but
peritonitis was not observed. Systemic
inflammation as determined by change in leukogram or plasma
fibrinogen was noted in one cow. The results of this study demonstrate that IP PPG is absorbed and eliminated rapidly in lactating dairy cows.