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The article presents a study on tissue residues of florfenicol in sheep. The purpose this study was to provide tissue residue data essential to accomplish the human food safety requirements for florfenicol in sheep and target animal safety data on injection site irritation. The researchers used high performance liquid chromatography (HPLC) with ultraviolet detection in distinguishing florfenicol amine in the target tissue from cattle treated with florfenicol.

Introduction: Prescribing fenbendazole medicated feed for pheasants in the USA is considered extra-label drug use under CPG Sec 615.115, and a safe estimated withdrawal interval (WDI) must be applied following administration to this minor food-producing species. This study sought to determine the pharmacokinetic and residue depletion profile for fenbendazole and its major metabolites to estimate a WDI for pheasants following fenbendazole administration as an oral medicated feed., Method: Pheasants ( n = 32) were administered fenbendazole as an oral medicated feed (100 ppm) for 7 days. Fenbendazole, fenbendazole sulfoxide, and fenbendazole sulfone (FBZ-SO 2 ) in liver and muscle samples were analyzed using HPLC-UV. Tissue WDIs were estimated using FDA, European Medicines Agency (EMA), and half-life multiplication methods for US poultry tolerances, EMA maximum residue limits, and the analytical limit of detection (LOD; 0.004 ppm). Terminal tissue elimination half-lives (T 1/2 ) were estimated by non-compartmental analysis using a naïve pooled data approach., Results: The tissue T 1/2 was 14.4 h for liver, 13.2 h for thigh muscle, and 14.1 h for pectoral muscle. The maximum estimated withdrawal interval was 153 h (7 days) for FBZ-SO 2 in pectoral muscle using the FDA tolerance method (95% confidence interval for the 99 th percentile of the population), and the LOD as the residue limit., Discussion: The results from this study support the use of FBZ-SO 2 as the marker residue in the liver of pheasants and the provision of evidence based WDIs following the extra-label administration of fenbendazole medicated feed (100 ppm) for 7 days., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Carreño Gútiez, Mercer, Martínez-López, Griffith, Wetzlich and Tell.)

Meloxicam is an anti-inflammatory drug used to treat pain and inflammation in ruminants including sheep, and pharmacokinetic studies are needed to protect the food supply from drug residues after use in food-producing animals. This study estimated plasma pharmacokinetic parameters and meat withdrawal intervals (WDI) for market sheep after multiple daily oral doses of meloxicam. Single and multiple dose plasma pharmacokinetic studies, a multi-dose tissue depletion study, and a follow-up study to investigate if events prior to slaughter were associated with differences in plasma meloxicam concentrations, all using sample data collected after completion of dosing, were completed. Using regulatory agency methods for calculating withdrawal times, an estimated WDI of at least 10 d following the last dose is recommended for market lambs treated with 10 daily oral 1 mg/kg doses of meloxicam tablets suspended in water. The effect of events surrounding slaughter on plasma meloxicam concentrations in lambs is unknown but should be considered if plasma samples are obtained immediately prior to or during the slaughter process and used for pharmacokinetic investigations.

Ceftiofur crystalline free acid (CCFA) is a third-generation, oil-based, cephalosporin antimicrobial marketed as a once weekly treatment in cattle and swine, and as a two-time dose with 10-day duration in horses. Because handling and restraint times can be reduced, long-acting antibiotic preparations are particularly useful for treatment of nondomestic species. This study evaluated the pharmacokinetics of CCFA in ringneck doves ( Streptopelia risoria ). A single intramuscular (IM) injection of CCFA at 50 mg/kg was administered to each of 30 doves, and blood was collected from subsamples of 6 birds at predetermined sampling times (i.e., with a postinjection range of 0.5 to 192 hr). All ringneck doves were scheduled for euthanasia because of reasons unrelated to the study; this was performed at the conclusion of the study; and complete postmortem and histopathologic examinations were performed. Plasma concentrations of CCFA remained above the minimum inhibitory concentration (1.0 µg/ml; observed for most avian pathogenic bacteria) for 108 hr. No abnormalities were identified on individual birds before and after clinical pathology results (i.e., hematocrits and plasma biochemistry profiles), and only minimal gross and histopathologic changes such as mild tissue inflammation at the injection site were observed. Based on these results, one IM injection of CCFA at 50 mg/kg seems to be a potential option for treatment of ringneck doves.

Objective: To determine the pharmacokinetics of ceftiofur sodium after IM and SC administration in green iguanas., Animals: 6 male and 4 female adult green iguanas., Procedure: In a crossover design, 5 iguanas received a single dose of ceftiofur sodium (5 mg/kg) IM, and 5 iguanas received the same dose SC. Blood samples were taken at 0, 20, and 40 minutes and 1, 2, 4, 8, 24, 48, and 72 hours after administration. After a 10-week washout period, each iguana was given the same dose via the reciprocal administration route, and blood was collected in the same fashion. Ceftiofur free-acid equivalents were measured via high-performance liquid chromatography., Results: The first phase intercepts were significantly different between the 2 administration routes. Mean maximum plasma concentration was significantly higher with the IM (28.6 +/- 8.0 microg/mL) than the SC (18.6 +/- 8.3 microg/mL) administration route. There were no significant differences between terminal half-lives (harmonic mean via IM route, 15.7 +/- 4.7 hours; harmonic mean via SC route, 19.7 +/- 6.7 hours) and mean areas under the curve measured to the last time point (IM route, 11,722 +/- 7,907 microg x h/mL; SC route, 12,143 +/- 9,633 microg x h/mL). Ceftiofur free-acid equivalent concentrations were maintained > or = 2 microg/mL for > 24 hours via both routes., Conclusions and Clinical Relevance: A suggested dosing schedule for ceftiofur sodium in green iguanas for microbes susceptible at > 2 microg/mL would be 5 mg/kg, IM or SC, every 24 hours.

Background: Competitive PCR of reverse transcribed mRNA sequences is used to quantify transcripts, but the usual approaches are labor-intensive and time-consuming. We describe the non-gel-based quantification of competitive reverse transcription (RT)-PCR products with use of microparticles and flow cytometry., Methods: PCR products of a target sequence and an internal control sequence (competitor) were labeled during PCR using digoxigenin (DIG)- and dinitrophenol (DNP)-labeled primer, respectively, allowing specific binding to microparticles coated with the corresponding antibody. Both amplification products were biotinylated to enable fluorescence labeling with streptavidin-R-phycoerythrin. The mean fluorescence intensity of each microparticle population, corresponding to the amount of bound PCR product, was measured in a flow cytometer. We constructed microparticles coated with antibodies against DIG and DNP to specifically capture PCR products derived from target and competitor sequences, respectively., Results: As required for a reliable competitive PCR assay, nearly identical kinetics were found for the amplification of target and competitor sequences when using only one competitive primer. The method was applied to examine interleukin-8 expression in human lymphocytes after x-irradiation. One hour after irradiation, the concentration of transcripts decreased by half., Conclusions: The flow cytometric assay for the quantification of competitive RT-PCR products avoids additional hybridization steps and antibody labeling. The use of paramagnetic microparticles would also enable the complete automation of this method.

Twelve (12) lactating dairy goats (46-71 kg body wt at study initiation) were divided into four treatment groups and dosed with ceftiofur sodium at 1.1 mg ceftiofur free acid equivalents (CFAE)/kg or 2.2 CFAE/kg using a complete two route (intravenous, i.v.; intramuscular, i.m.), two-period crossover design, with a 2-week washout between injections. After another 2-week washout period, the goats were dosed with ceftiofur sodium i.m. for 5 consecutive days at either 1.1 or 2.2 mg CFAE/kg. The goats from the 2.2 mg/kg multiple dose group were dried off and the i.v. kinetic study repeated. After all injections, blood samples were obtained serially for determination of combined serum concentrations of ceftiofur and metabolites. After intravenous doses of 1.1 and 2.2 mg/kg, the harmonic means of the terminal phase half-lives were 171.8 and 233 min, respectively, for lactating does. The harmonic mean of the terminal phase half-life after an i.v. dose of 2.2 mg/kg in non-lactating does was 254 min. The AUC0-infinity was significantly less and the clearance significantly greater during lactation. After i.m. doses of 1.1 and 2.2 mg/kg, the harmonic mean terminal phase half-lives were 163 and 156 min, respectively. The i.m. bioavailability of ceftiofur sodium in goats was 100%, and the AUC0-infinity was dose-proportional from 1.1-2.2 mg CFAE/kg body weight. After five daily i.m. doses of ceftiofur sodium at either 1.1 or 2.2 mg CFAE, there was minimal accumulation of drug in serum as assessed by Cmax, and serum concentrations were dose-proportional after the multiple dosing regimen.