Withdrawal of cefoperazone with milk after intramammary administration in dairy cows - prospective and retrospective analysis.

The aim of the study was to carry out retrospective and prospective comparative analyses of the pharmacokinetics of CEF after single intramammary (IMM) administration in cows. The prospective study (study A) was conducted on 9 dairy cows of the Polish Black-White race with clinical mastitis during the lactation period. Milk samples were collected at 2, 4, 6, 8, 10, 24, 36, 48, 72 and 84 h after single IMM administration of 250 mg of CEF to one quarter. Drug concentrations in milk samples were determined by HPLC-MS/MS technique and the results of the pharmacokinetic analysis were compared to those obtained in previous studies based on the microbiological (study B) and HPLC-UV methods (study C and D). Pharmacokinetic parameters were calculated based on adapted two-compartment model of drug distribution. One of the findings of the comparison of the analysed investigations is that the CEF kinetics determined with the microbiological method is consistent with the results obtained by the authors of this paper. Both studies yielded similar results of the key pharmacokinetic parameters related to the level of the drug distribution to tissues and elimination half-life. In the pharmacodynamic analysis, the observations in all four studies were entirely consistent and have shown lower values of T>MIC90 in healthy animals and significantly higher values in infected dairy cows. The comparison of studies A, B, C, and D revealed that the time of complete CEF wash-out of 90.90% varied and amounted to 5.7, 8.0, 2.2, and 2.2 days after administration of the drug, respectively. It was confirmed that not only the type of the analytical method but also correct sampling have a significant impact on determination of the correct value of the drug half-life after IMM administration. The comparative analysis of studies in which the milk yield was high and low allows a conclusion that this parameter in the case of CEF has no significant effect on T>MIC90.

The influence of Actinobacillus pleuropneumoniae infection on tulathromycin pharmacokinetics and lung tissue disposition in pigs.

A tulathromycin concentration and pharmacokinetic parameters in plasma and lung tissue from healthy pigs and Actinobacillus pleuropneumoniae (App)-infected pigs were compared. Tulathromycin was administered intramuscularly (i.m.) to all pigs at a single dose of 2.5 mg/kg. Blood and lung tissue samples were collected during 33 days postdrug application. Tulathromycin concentration in plasma and lung was determined by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) method. The mean maximum plasma concentration (Cmax ) in healthy pigs was 586 ± 71 ng/mL, reached by 0.5 h, while the mean value for Cmax of tulathromycin in infected pigs was 386 ± 97 ng/mL after 0.5 h. The mean maximum tulathromycin concentration in lung of healthy group was calculated as 3412 ± 748 ng/g, detected at 12 h, while in pigs with App, the highest concentration in lung was 3337 ± 937 ng/g, determined at 48 h postdosing. The higher plasma and lung concentrations in pigs with no pulmonary inflammation were observed at the first time points sampling after tulathromycin administration, but slower elimination with elimination half-life t1/2el  = 126 h in plasma and t1/2el  = 165 h in lung, as well as longer drug persistent in infected pigs, was found.

Multi-residue determination of antibiotics in fish by liquid chromatography-tandem mass spectrometry.

A multi-residue method for the determination of 34 antibacterial drugs (three aminoglycosides, nine ß-lactams, nine fluoroquinolones, three macrolides, five sulfonamides, trimethoprim and four tetracyclines) in fish samples by LC-MS/MS was developed. The procedure enables the isolation of residues based on double extraction of the fish sample with m-phosphoric acid and heptafluorobutyric acid as an ion-pair agent and acetonitrile. All compounds were determined at the same time on a C18 column with gradient elution. The method was validated according to the requirements of European Decision 2002/657/EC. Specificity, recovery, repeatability, within-laboratory reproducibility, decision limit CCα and detection capability CCß were calculated. CCα ranged from 55.3 to 1085 µg kg(-1) and CCß ranged from 59.5 to 1141 µg kg(-1). The overall recoveries were from 96% to 111% with respect to the internal standards.