Clinical pharmacokinetics of carbenicillin, carfecillin, ticarcillin and BL‐P 1654 in dairy cows

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Abstract
The minimal inhibitory concentrations (MIC) of carbenicillin, ticarcillin and BL-P-1654 for gram-negative udder pathogens were determined using the agar plate dilution method. The MIC of the drugs for 50 and 90% of the isolates examined ranged for Escherichia coli and Aerobacter spp. from 1.56-25 .mu.g/ml, and for Klebsiella spp. and Pseudomonas spp. from 3.12-50 .mu.g/ml. Serratia spp. were relatively non-susceptible for the drugs studied (MIC > 50 .mu.g/ml). Each drug was administered i.v. at 5 g and 15 g/cow to different groups of cows with normal and inflamed quarters of the udder. Distribution and elimination kinetic parameters calculated from serum drug level data were very similar to those of other .beta.-lactam antibiotics. Although drug concentrations in milk from inflamed quarters were higher than in milk from normal quarters, they were considerably below the MIC for the majority of gram-negative udder pathogens. Evidently, parenteral treatment of gram-negative udder infections with carbenicillin, carfecillin, ticarcillin and BL-P-1654 at the dose levels used in the present study is unlikely to result in a bacteriological cure and would probable be clinically ineffective.