Intramuscular Pharmacokinetics and Milk Levels of Ceftriaxone in Endometritic Cows.

Disease conditions are known to alter the pharmacokinetics of antibacterials in bovines. Ceftriaxone is effective for the treatment of bacterial endometritis particularly caused by Gram-negative pathogens. In this regard, the plasma pharmacokinetics and milk levels of ceftriaxone were studied in healthy and endometritic cows following single intramuscular administration. Peak plasma drug levels of 11.2 ± 0.329 and 4.68 ± 0.261 μg.ml-1 attained at 30 minutes were found in healthy and endometritic cows, respectively. The drug was detected above the minimum inhibitory concentration (MIC) after up to 6 h of dosing and the disposition followed a one-compartment open model. The values of Vdarea (apparent volume of distribution), AUC (area under the plasma drug concentration-time curve), t1/2β (elimination half life) and P/C ratio (ratio of drug present in peripheral versus central compartment) were 0.67 ± 0.13 L.kg-1, 21.3 ± 0.86 μg.ml-1.h, 1.42 ± 0.13 h and 1.07 ± 0.25, respectively, in healthy cows and 1.35 ± 0.19 L.kg-1, 12.4 ± 0.56 μg.ml-1.h, 1.69 ± 0.47 h and 0.92 ± 0.39, respectively, in endometritic cows. The use of antibacterial drugs that could penetrate into the udder parenchyma in therapeutic levels is of considerable importance in severe infectious conditions of the udder. Ceftriaxone was secreted into milk up to 36 h of administration. An appropriate intramuscular dosage for ceftriaxone, would be 13 mg.kg-1 repeated at 6 h intervals for the treatment of endometritis in cows. [ABSTRACT FROM AUTHOR]