This study describes the pharmacokinetic profile of procaine penicillin G after intraperitoneal (IP) administration in 8 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 detection (LOD) of 5 ppb for plasma and milk samples. Noncompartmental methods were used to analyze plasma kinetics. The mean pharmacokinetic parameters (} s.d.) were: Cmax, 5.5 } 2.6 Êg/mL; Tmax, 0.75 } 0.27 h; AUC0-, 10.8 } 4.9 Êg*h/mL; MRT, 2.2 } 0.9 h. All milk from treated cows contained penicillin residues for a minimum of 3 milkings (31 h) and maximum of 5 milkings (52 h) after administration. Concentrations of penicillin G in all muscle, liver, and kidney samples taken 10 days post-administration were below the limit of detection. Necropsy examinations revealed foci of hemorrhage on the rumenal omentum of most cows but peritonitis was not observed. Systemic inflammation as determined by altered leukograms and fibrinogen was noted in one cow. The results of this study demonstrate that IP procaine penicillin G is absorbed and eliminated rapidly in lactating dairy cows.

This study describes the pharmacokinetic profile of procaine penicillin G after intraperitoneal (IP) administration in 8 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 detection (LOD) of 5 ppb for plasma and milk samples. Noncompartmental methods were used to analyze plasma kinetics. The mean pharmacokinetic parameters (} s.d.) were: Cmax, 5.5 } 2.6 Êg/mL; Tmax, 0.75 } 0.27 h; AUC0-, 10.8 } 4.9 Êg*h/mL; MRT, 2.2 } 0.9 h. All milk from treated cows contained penicillin residues for a minimum of 3 milkings (31 h) and maximum of 5 milkings (52 h) after administration. Concentrations of penicillin G in all muscle, liver, and kidney samples taken 10 days post-administration were below the limit of detection. Necropsy examinations revealed foci of hemorrhage on the rumenal omentum of most cows but peritonitis was not observed. Systemic inflammation as determined by altered leukograms and fibrinogen was noted in one cow. The results of this study demonstrate that IP procaine penicillin G is absorbed and eliminated rapidly in lactating dairy cows.