Fluoroquinolones are extensively used in the treatment of systemic bacterial infections in poultry, including systemic Escherichia coli bacillosis, which is a common disease in turkey flocks. Marbofloxacin has been licensed for use in various mammalian species, but not as yet for turkeys, although its kinetic properties distinguish it from other fluoroquinolones. For example, the longer half-life of marbofloxacin in many animal species has been appreciated in veterinary practice. It is generally accepted that, for fluoroquinolones, the optimal dose should be estimated on the basis of the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of the drug under consideration. Knowledge of these specific data for the target animal species allows the establishment of an integrated PK-PD model that is of high predictive value. In the present study, the antibacterial efficacy (PD indices) against a field isolate of Escherichia coli O78/K80 was investigated ex vivo following oral and intravenous administration of marbofloxacin to turkeys (breed BUT 9; six animals per group) at a dose of 2 mg/kg of body weight (BW). At the same time, the serum concentrations of marbofloxacin were measured at different time intervals by a standardized high-performance liquid chromatography method, allowing the calculation of the most relevant kinetic parameters (PK parameters). The in vitro serum inhibitory activity of marbofloxacin against the selected E. coli strain, O78/K80, was 0.5 g/ml in the blood serum of turkeys, and the ratio of the maximum concentration of the drug in serum to the serum inhibitory activity was 1.34. The lowest ratio of the measured serum concentration multiplied by the incubation period of 24 h to the serum inhibitory activity required for bacterial elimination was lower than the ratio of the area under the serum concentration-time curve (AUC) to the serum inhibitory activity. These first results suggested that the recommended dose of 2 mg/kg BW of marbofloxacin is sufficient to achieve a therapeutic effect in diseased animals. However, considering the risk of resistance induction, the applied dose should be equal to an AUC/MIC of >125, the generally recommended dose for all fluoroquinolones. According to the PK-PD results presented here, a dose of 3.0 to 12.0 mg/kg BW per day would be needed to meet this criterion. In conclusion, the results of the present study provide the rationale for an optimal dose regimen for marbofloxacin in turkeys and hence should form the basis for dose selection in forthcoming clinical trials.Marbofloxacin is a synthetic fluoroquinolone, developed for veterinary use only (47). It has a broad spectrum of activity (58), and bactericidal concentration-dependent killing is observed against many gram-negative bacteria (12, 49, 51, 52). The pharmacokinetic (PK) properties of marbofloxacin have been studied in several mammalian species, and some advantages over other fluoroquinolones, such as a longer elimination half-life, have been described (2,43,47,48). In practice, this would e...

Colibacillosis is a systemic disease responsible for important economic losses in poultry breeding; fluoroquinolones, including danofloxacin, are used to treat diseased animals. The purpose of the present study was to estimate pharmacokinetic-pharmacodynamic (PK-PD) surrogates for bacteriostasis, bactericidal activity and bacterial elimination against Escherichia coli O78/K80, using a PK-PD approach, for danofloxacin in turkeys after oral administration. Eight healthy turkeys, breed BUT 9, were included in a two-way crossover study. The drug was administered intravenously (i.v.) and orally at a dose rate of 6 mg/kg bw. The values of the elimination half-life and the total body clearance after i.v. administration were 8.64 +/- 2.35 h and 586.76 +/- 136.67 ml kg(-1)h(-1), respectively. After oral administration, the values of the absolute bioavailability and the elimination half-life were 78.37+/- 17.35% and 9.74+/- 2.93 h, respectively. The minimum inhibitory concentration against the investigated strain in turkey serum was 0.25 microg/ml, four times higher than in broth. The lowest effective ex vivo AUC(24)/MIC ratios required for bacteriostasis, bactericidal activity, and total killing of E. coli O78/K80 were 0.416 h, 1.9 h and 6.73 h, respectively. The oral dose of 6 mg/kg used in the present study could be interpreted as being sufficient to eliminate E. coli with an MIC 0.25 microg/ml. However, considering the demand that antimicrobial resistance should be avoided by complete bacterial elimination, PK-PD considerations suggest that an even higher dose of 32 mg/kg per day or 0.7 mg/kcal per day should be evaluated in clinical trials.

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1. The pharmacokinetics of danofloxacin was investigated in common pheasants, guinea fowls and Japanese quails after intravenous (i.v.) and oral (p.o.) administration at a dose of 10 mg kg(-1) body weight. Concentrations of the drug in serum were determined by high-performance liquid chromatography. The values of the pharmacokinetic parameters after both applications were calculated on the basis of a one-compartment model. 2. The elimination half-lives after i.v. injection were 6.82 ± 1.87, 3.31 ± 0.13 and 3.84 ± 0.89 h in pheasants, guinea fowls and quails, respectively. Total body clearance values were 0.45 ± 0.16, 1.23 ± 0.07 and 1.61 ± 0.34 l h(-1) kg(-1) in pheasants, guinea fowls and quails, respectively. 3. After p.o. administration, maximum serum concentrations were 0.54 ± 0.26, 0.51 ± 0.12 and 0.78 ± 0.11 μg ml(-1) respectively, reached at 2.04 ± 0.23, 10.4 ± 5.64 and 5.35 ± 0.47 h. Oral bioavailability values were 82.32% for pheasants, 79.46% for guinea fowls and 83.5% for Japanese quails. Pharmacokinetic/pharmacodynamic (PK/PD) predictive indices were also calculated and compared.