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Abstract

OBJECTIVE To determine the pharmacokinetics of voriconazole administered PO with or without food to red-tailed hawks (Buteo jamaicensus) and whether any observed variability could be explained by measured covariates to inform dose adjustments.

ANIMALS 7 adult red-tailed hawks.

PROCEDURES In a crossover study design, hawks were randomly assigned to first receive voriconazole (15 mg/kg, PO) injected into a dead mouse (n = 3; fed birds) or without food (4; unfed birds). Sixteen days later, treatments were reversed. Blood samples were collected at various points to measure plasma voriconazole concentrations by ultraperformance liquid chromatography. Pharmacokinetic data were analyzed by noncompartmental methods and fit to a compartmental model through nonlinear mixed-effects regression, with feeding status and body weight investigated as covariates.

RESULTS Voriconazole was well absorbed, with quantifiable plasma concentrations up to 24 hours after administration. Mean plasma half-life was approximately 2 hours in fed and unfed birds. Administration of the voriconazole in food delayed absorption, resulting in a significant delay in time to maximum plasma concentration. The final compartmental model included a categorical covariate to account for this lag in absorption as well as body weight as a covariate of total body clearance (relative to unknown bioavailability).

CONCLUSIONS AND CLINICAL RELEVANCE A single dose of voriconazole (15 mg/kg) administered PO to red-tailed hawks resulted in mean plasma voriconazole concentrations greater than the targeted value (1 μg/mL). Additional studies with larger sample sizes and multidose regimens are required before the model developed here can be applied in clinical settings.

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in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the elimination kinetics of ceftiofur hydrochloride in milk after intramammary administration in lactating dairy cows.

Design—Prospective study.

Animals—5 lactating dairy cows.

Procedure—After collection of baseline milk samples, 300 mg (6 mL) of ceftiofur was infused into the left front and right rear mammary gland quarters of each cow. Approximately 12 hours later, an additional 300 mg of ceftiofur was administered into the same mammary gland quarters after milking. Milk samples were collected from each mammary gland quarter every 12 hours for 10 days. Concentrations of ceftiofur and its metabolites in each milk sample were determined to assess the rate of ceftiofur elimination.

Results—Although there were considerable variations among mammary gland quarters and individual cows, ceftiofur concentrations in milk from all treated mammary gland quarters were less than the tolerance (0.1 µg/mL) set by the FDA by 168 hours (7 days) after the last intramammary administration of ceftiofur. No drug concentrations were detected in milk samples beyond this period. Ceftiofur was not detected in any milk samples from nontreated mammary gland quarters throughout the study.

Conclusions and Clinical Relevance—Ceftiofur administered by the intramammary route as an extralabel treatment for mastitis in dairy cows reaches concentrations in milk greater than the tolerance set by the FDA. Results indicated that milk from treated mammary gland quarters should be discarded for a minimum of 7 days after intramammary administration of ceftiofur. Elimination of ceftiofur may be correlated with milk production, and cows producing smaller volumes of milk may have prolonged withdrawal times. (J Am Vet Med Assoc 2004;224:1827–1830)

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in Journal of the American Veterinary Medical Association

The FARAD manages the Food Animal Residue Avoidance Databank and has been serving the veterinary profession for 35 years. It is funded and sponsored by the USDA National Institute of Food and Agriculture and is overseen and operated by faculty and staff within the colleges of veterinary medicine at the University of California-Davis, University of Florida, Kansas State University, and North Carolina State University.

The overarching goal of FARAD is to provide veterinary practitioners the most current and accurate information to facilitate the production of safe foods of animal origin through the prevention and mitigation of violative chemical (eg,

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in Journal of the American Veterinary Medical Association

In recent years, backyard poultry flocks have become increasingly popular in urban areas throughout the United States. Results of a 2010 USDA study 1 of 4 US cities (Denver, Los Angeles, Miami, and New York) indicated that 1% of households surveyed owned chickens and another 4% of households surveyed were planning on owning chickens within the next 5 years. The increase in the number of small poultry flocks in urban areas has led to an increase in the demand for veterinary services for those flocks, and veterinarians whose clientele is usually limited to companion animals now find themselves treating

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To investigate the feasibility of using multivariate cluster analysis to meta-analyze pharmacokinetic data obtained from studies of pharmacokinetics of ampicillin trihydrate in cattle and identify factors that could account for variability in pharmacokinetic parameters among studies.

Sample Population—Data from original studies of the pharmacokinetics of ampicillin trihydrate in cattle in the database of the Food Animal Residue Avoidance Databank.

Procedure—Mean plasma or serum ampicillin concentration versus time data and potential factors that may have affected the pharmacokinetics of ampicillin trihydrate were obtained from each study. Noncompartmental pharmacokinetic analyses were performed, and values of pharmacokinetic parameters were clustered by use of multivariate cluster analysis. Practical importance of the clusters was evaluated by comparing the frequency of factors that may have affected the pharmacokinetics of ampicillin trihydrate among clusters.

Results—A single cluster with lower mean values for clearance and volume of distribution of ampicillin trihydrate administered PO, compared with other clusters, was identified. This cluster included studies that used preruminant calves in which feeding was withheld overnight and calves to which probenecid had been administered concurrently.

Conclusions and Clinical Relevance—Meta-analysis was successful in detecting a potential subpopulation of cattle for which factors that explained differences in pharmacokinetic parameters could be identified. Accurate estimates of pharmacokinetic parameters are important for the calculation of dosages and extended withdrawal intervals after extralabel drug administration. (Am J Vet Res 2005;66:108–112)

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in American Journal of Veterinary Research

Calfhood diseases have major negative economic consequences on beef and dairy operations owing to costs associated with treatment, long-term effects on growth and performance, and death of affected calves. 1–3 The number of drugs approved for the treatment of diseased calves by the FDA is limited; however, veterinarians have the authority to administer drugs in an extralabel manner to that class of animals under provisions established by AMDUCA. 4 Nevertheless, drug labels that state, “a withdrawal period has not been established for this product in preruminating calves” can cause confusion about whether those drugs can or cannot be

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in Journal of the American Veterinary Medical Association