Rapid and Online Microvolume Flow-Through Dialysis Probe for Sample Preparation in Veterinary Drug Residue Analysis.

A rapid and online microvolume flow-through dialysis probe designed for sample preparation in the analysis of veterinary drug residues is introduced. This study addresses the need for efficient and green sample preparation methods that reduce chemical waste and reagent use. The dialysis probe integrates with liquid chromatography and mass spectrometry (LC-MS) systems, facilitating automated, high-throughput analysis. The dialysis method utilizes minimal reagent volumes per sample, significantly reducing the generation of solvent waste compared to traditional sample preparation techniques. Several veterinary drugs were spiked into tissue homogenates and analyzed to validate the probe's efficacy. A diagnostic sensitivity of >97% and specificity of >95% were obtained for this performance evaluation. The results demonstrated the effective removal of cellular debris and particulates, ensuring sample integrity and preventing instrument clogging. The automated dialysis probe yielded recovery rates between 27 and 77% for multiple analytes, confirming its potential to streamline veterinary drug residue analysis, while adhering to green chemistry principles. The approach highlights substantial improvements in both environmental impact and operational efficiency, presenting a viable alternative to conventional sample preparation methods in regulatory and research applications.

Heart-Cutting Bidimensional Liquid Chromatography for the Simultaneous Analysis of Veterinary Drugs Residues and Nucleotide Monophosphates in Sheep's Milk.

Sheep's milk is a significant source of nucleotide monophosphates (NMPs) but can also contain undesirable residues from veterinary drugs, posing a potential human health risk. This study introduces a novel application of two-dimensional liquid chromatography (2D-LC), in heart-cutting mode, for the simultaneous determination of nucleotides and veterinary drug residues in sheep's milk. 2D-LC allows for the separation of these compounds in a single chromatographic run despite their differing physicochemical properties. The proposed method separates six veterinary drug residues and five NMPs in a single injection. The compounds were separated using a C18 reversed-phase column in the first dimension and a Primesep SB analytical column in the second dimension. The method performance was evaluated in terms of linearity range, detection and quantification limits, matrix effects, precision, and accuracy. The results demonstrated good linearity and sensitivity, with quantification limits allowing for the quantification of veterinary drugs at the maximum residue level and nucleotides at typical levels found in milk samples. The method has been successfully applied to the analysis of sheep's milk samples acquired from local supermarkets, with recoveries within a range of 70-119% and 82-117% for veterinary residues and NMPs, respectively.

Optimization and validation of high-performance liquid chromatography using modified QuEChERS to determine anthelmintic drugs in mutton.

The aim of this study was to rapidly determine the presence of anthelmintic drugs in sheep meat using the optimized high-performance liquid chromatography-ultraviolet (HPLC-UV) method with modified QuEChERS (quick, easy, cheap, effective, rugged, safe) technology. Fifty fresh sheep meat samples from different slaughterhouses were collected. A double extraction procedure (QuEChERS/HPLC-UV technology) was used to extract the target analytes. A multilevel calibration curve from 1 to 1000 g/kg was used to establish instrument linearity for rafoxanide, albendazole, and closantel, whereas 0.1-100 µg/kg was used for ivermectin, levamisole, and oxyclozanide to find the lowest concentration, maximum residue limit (MRL), and occupied range for targeted analytes. The concentration levels were used to investigate the linearity, whereas several certified reference materials were applied to determine accuracy. The process was linear for all combinations, from the limit of quantification (LOQ) to the maximum concentration. The LOQ was established at 0.5 µg/kg for ivermectin, levamisole, and oxyclozanide and 10 µg/kg for rafoxanide, albendazole, and closantel. Recovery values were 70%-120%, and repeatability/reproducibility stated in relative standard deviation was obtained at less than 20%. QuEChERS method revealed that most meat samples contained anthelmintic drug residues, of which the majority exceeded the MRLs. Thus, the drugs should be used correctly in animals to avoid residues in food for human consumption.

Mass Balance Studies of Robenidine Hydrochloride in the Body of Channel Catfish (Ictalurus punctatus).

This study aims to determine the mass balance of robenidine hydrochloride (ROBH) in the body of Channel catfish (Ictalurus punctatus). ROBH was administered orally at a dose of 20 mg/kg; following drug administration, the water samples were collected at predetermined time points (12, 24, 48, 72, 96, 120, 144, and 168 h), the experimental fish were executed after the water samples were obtained at 168 h, and the tissue samples were collected separately from the bones. The water and tissue samples were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) for concentrations of ROBH and its potential major metabolites, 4-chlorohippuric acid (PCHA) and 4-chlorobenzoic acid (PCBA). The tissue samples were prepared using a modified QuEChERS procedure; the water samples were prepared using a liquid-liquid extraction (LLE) procedure. The results show that the recovery rate of ROBH in fish is very low, less than 2% of the total amount of the drug, and the recovery in water can reach 80.7% of the total amount of the drug. The content of PCBA accounted for 42.4% of the total amount of the drug; the content of ROBH accounted for 38.3% of the total amount of the drug. The content of PCHA accounted for less than 1% of the total amount of the drug. The results show that, after a single administration, ROBH is rapidly metabolized in vivo and excreted in the form of ROBH as well as metabolite PCBA. ROBH and PCBA can be used as the main targets for the metabolism detection of ROBH in Channel catfish.

Pharmacokinetics, Tissue Residues, and Withdrawal Times of Oxytetracycline in Rainbow Trout (Oncorhynchus mykiss) after Single- and Multiple-Dose Oral Administration.

The aim of this study was to compare the pharmacokinetics of oxytetracycline (OTC) following single- (60 mg/kg) and multiple-dose oral administrations (60 mg/kg, every 24 h for 7 days) in rainbow trout. It also aimed to determine bioavailability after a single dose and tissue residues and withdrawal times after multiple doses. This study was carried out on 420 rainbow trout at 9 ± 0.8 °C. This study was carried out in two stages: single-dose (intravascular and oral) and multiple-dose treatment. The OTC concentrations in plasma and tissues were measured by high-performance liquid chromatography and analyzed by a non-compartmental method. The withdrawal time (WT) was estimated using the WT 1.4 software. OTC exhibited a long terminal elimination half-life (t1/2ʎz) after IV and oral administration. The oral bioavailability of OTC was very low (2.80%). In multiple-dose treatment, t1/2ʎz, the area under the plasma concentration-time curve and peak plasma concentration increased significantly after the last day compared to the first day. OTC showed strong accumulation after multiple doses with a value of 5.33. OTC concentrations were obtained in the order liver > kidney > muscle+skin > plasma. At 9 ± 0.8 °C, the WT calculated for muscle+skin was 56 days for Europe and 50 days for China, respectively. The t1/2ʎz (68.94 h) and time (68 h) above the 1 µg/mL MIC following a single OTC dose may support the extension of the 24 h dosing interval following multiple dosing. However, further studies are required to determine the optimal dosage regimen in multiple-dose OTC treatment in the treatment of infections caused by susceptible pathogens.

Pharmacokinetics, tissue residue depletion, and withdrawal interval estimations of florfenicol in goats following repeated subcutaneous administrations.

Florfenicol is a broad-spectrum antibiotic commonly used in the U.S. to treat respiratory and enteric infections in goats in an extra-label manner, which requires scientifically based withdrawal intervals (WDIs) for edible tissues. This study aimed to determine the depletion profiles for florfenicol and florfenicol amine in plasma and tissues samples and to estimate WDIs for goats following subcutaneous injection of 40 mg/kg florfenicol, twice, 96 h apart. The samples were collected up to 50 days after the second dose. Pharmacokinetic parameters were calculated using non-compartmental analysis. Three different pharmacostatistical methods with different operational tolerances were used to calculate WDIs. The plasma half-life was 101.80 h for florfenicol and 207.69 h for florfenicol amine after the second dose. Using the FDA tolerance limit method, WDIs were 202 and 101 days, while the EMA maximum residue limit method estimated 179 and 96 days for the respective tissue concentrations to fall below limits of detection (0.12 µg/g for liver and 0.05 µg/g for kidney). This study characterizes plasma pharmacokinetics and tissue depletion profiles of florfenicol and florfenicol amine in goats following subcutaneous injections and reports estimated WDIs for food safety assessment of florfenicol in goats.

Recent Advances in the Determination of Veterinary Drug Residues in Food.

The presence of drug residues in food products has become a growing concern because of the adverse health risks and regulatory implications. Drug residues in food refer to the presence of pharmaceutical compounds or their metabolites in products such as meat, fish, eggs, poultry and ready-to-eat foods, which are intended for human consumption. These residues can come from the use of drugs in the field of veterinary medicine, such as antibiotics, antiparasitic agents, growth promoters and other veterinary drugs given to livestock and aquaculture with the aim of providing them as prophylaxis, therapy and for promoting growth. Various analytical techniques are used for this purpose to control the maximum residue limit. Compliance with the maximum residue limit is very important for food manufacturers according to the Food and Drug Administration (FDA) or European Union (EU) regulations. Effective monitoring and control of drug residues in food requires continuous advances in analytical techniques. Few studies have been reviewed on sample extraction and preparation techniques as well as challenges and future directions for the determination of veterinary drug residues in food. This current review focuses on the overview of regulations, classifications and types of food, as well as the latest analytical methods that have been used in recent years (2020-2023) for the determination of drug residues in food so that appropriate methods and accurate results can be used. The results show that chromatography is still a widely used technique for the determination of drug residue in food. Other approaches have been developed including immunoassay, biosensors, electrophoresis and molecular-based methods. This review provides a new development method that has been used to control veterinary drug residue limit in food.

Detection of Doxycycline Using Carbon Quantum dots as Probe Based on Internal Filtering Effect.

The establishment of a convenient and effective detection method for doxycycline (DC) holds significant importance in drug monitoring and drug residue assessment. In this work, carbon quantum dots (CQDs) with excellent and stable luminescence performance (the quantum yield of CQDs was 21.8%) were synthesized by the melting method and employed as probes to monitor the fluorescence intensity variations before and after the introduction of DC. A fluorescence analytical method based on the internal filtration effect (IFE) was developed for DC determination. The mechanism of DC quenching CQDs was verified using fluorescence lifetime tests, absorption spectroscopy, and evaluation of internal filtration parameters. After optimizing experimental conditions, it was found that the DC concentration (CDC) exhibited a good linear relationship with the fluorescence quenching efficiency ((F0-F)/F0) of CQDs in the range of 5-30 µM. The fitted linear equation was Y = 0.01249*CDC+0.03625, R2 = 0.9987, and the detection limit was 2.343 µM (n = 8). This developed method has been successfully applied to accurately determine DC concentrations in both doxycycline hydrochloride tablets and human serum samples. It stands out for its simplicity, rapidity, and acceptable detection performance. Due to its advantages, this method holds great promise for application in the biomedical field for monitoring DC drug concentrations and ensuring quality control.

Transfer of ß-lactam and tetracycline antibiotics from spiked bovine milk to Dambo-type cheese, whey, and whey powder.

The aim of this study was to investigate the transfer of residues of five ß-lactam antibiotics (ampicillin, penicillin G, cloxacillin, dicloxacillin and cephalexin) and two tetracyclines (tetracycline and oxytetracycline) in the processing of cheese and whey powder, evaluating the effect of the processes and the final concentration in each product generated. Raw milk was fortified at two concentration levels with the seven antibiotics. The first concentration level (C1) was chosen according to the maximum residue limit (MRL) of each antibiotic (ampicillin and penicillin G: 4 µg kg-1; cloxacillin and dicloxacillin: 30 µg kg-1; cephalexin, tetracycline and oxytetracycline: 100 µg kg-1). The second concentration level (C2) was spiked as follows according to each antibiotic: 0.5 MRL (cloxacillin, dicloxacillin, cephalexin), 0.1 MRL (tetracycline and oxytetracycline) and 3 MRL (ampicillin and penicillin G). The antibiotics were analyzed by LC-MS/MS. No ampicillin or penicillin G residues were found in cheese or whey powder, although they were detected in whey at concentrations similar to those added to raw milk. Cephalexin was mostly distributed in whey between 82% and 96%, being the antibiotic that presented the highest concentration in whey powder (784 ± 98 µg kg-1) when milk was spiked at the MRL. The whey distribution of cloxacillin and dicloxacillin ranged from 57% to 59% for cloxacillin and from 46% to 48% for dicloxacillin, and both concentrated in whey powder. Tetracyclines were the antibiotics that concentrated in cheese, with retentions between 75% and 80% for oxytetracycline and between 83% and 87% for tetracycline. The distribution of antibiotics in the dissimilar stages of the cheese and whey powder production processes, as well as their concentration in the final products, depend on each type of antibiotic. Knowledge of the transfer of antibiotic residues during the process and final disposal is an input for the risk assessment of their consumption.

In Vivo Evaluation of an Ivermectin and Allicin Combination Treatment for Eradicating Poultry Red Mite.

A safe and effective method for eradicating poultry red mite (PRM; Dermanyssus gallinae) is urgently needed, as existing treatments show a low efficacy or hazardous effects on chickens. We evaluated the efficacy of a combined treatment with ivermectin and allicin (IA) against PRMs in chickens and drug residues in non-target samples. The efficiency of PRM eradication by IA was compared with those of natural acaricides in vitro. Ivermectin (0.25 mg/mL) + allicin (1 mg/mL) (IA compound) was sprayed on isolator housing hens with PRMs. The PRM mortality rate, clinical symptoms, and ivermectin residue in hens were analyzed. IA showed the highest PRM-eradication efficacy among all tested compounds in vitro. The insecticidal rates of IA were 98.7%, 98.4%, 99.4%, and 99.9% at 7, 14, 21, and 28 days of treatment, respectively. After inoculating PRMs, hypersensitivity, itching, and a pale-colored comb were observed in control animals, which were absent in treated hens. No clinical symptoms from IA and ivermectin residues were found in hens. IA effectively exterminated PRMs, demonstrating its potential for industrial use to treat PRMs.

Multi-factorial investigation of the effect of biochar of the secondary medicinal residue of snow lotus on the adsorption of two azo dyes, methyl red and methyl orange.

Azo dye residues pollute water, which are difficult to decompose, and posing a major threat to the ecological environment. The residues of Chinese medicine still have many possibilities for use after its medicinal value has been brought into play. In this study, secondary residue biochar activation (Na2 CO3 -modified, SBA) and secondary residue biochar (unmodified, SBC) were prepared from the secondary residue of snow lotus at 200-600°C. Surface features were obtained by Brunauer-Emmett-Teller N2 method and combined with scanning electron microscopy, and their structures were analyzed by x-ray diffraction spectroscopy, Fourier infrared and near-infrared spectroscopy. The effects of five factors, including initial concentration, contact time and adsorption temperature and so forth, on the adsorption of methyl red (MR) and methyl orange (MO) solutions were investigated. Results showed that the biochar yield, specific surface area, and pore size increased after modification. modification promoted the formation of the internal structure aromatization and oxygen-containing functional groups. Adsorption experiments showed that the surroundings pH = 8, the dyes adsorption concentration of 8 mg/L, adsorption temperature of 20-40°C and time of about 1 h were more stable. Under the condition, the removal of MO by SBA could reach approximately 60%-80% (480-640 mg/g), while the removal of MR could reach more than 90% (>720 mg/g).The charcoal prepared and modified under high temperature conditions was more effective for MO adsorption, while MR relied on low temperature effectively. This study provides a new choice of adsorbent for MR and MO and finds a new direction for the utilization of snow lotus residues.

Comprehensive stability study of benzimidazole drug residues in standard solution, muscle and milk.

The performance criteria of analytical methods and the necessity for stability analysis to provide the accuracy of the results of the analyzed samples are explained in European Commission Decision 2021/808/EC and the guidance document SANTE/2021/11312. Detection of time-dependent changes in drug concentrations during storage or transport and re-analysis of samples are crucial to obtain high-quality results and reliable data. In this way, it allows toxicologists to interpret the analytical results accurately in drug analyses. The aim of this study was comprehensively to investigate the stability of benzimidazoles (levamisole hydrochloride, albendazole, albendazole-sulfone, albendazole-2-amino sulfone, albendazole sulfoxide, oxfendazole, 5-hydroxythiabendazole, triclabendazole, ketotriclabendazole, thiabendazole, flubendazole, fenbendazole sulfone) in working solutions, muscle and milk samples. For this purpose, long-term stability was evaluated over 6 months and under four different storage conditions (4 °C, -20 °C, 20 °C light and 20 °C dark) in the matrix. The influences of three freeze-thaw cycles, autosampler stability, and 60 min storage at 40 °C were investigated for short-term stability. Simultaneously, the stability of the working solutions were established over 6 months and under five different conditions (4 °C, -20 °C, -80 °C, 20 °C light, and 20 °C dark). It was found that working solutions can be stored at -80 °C or -20 °C, and it is appropriate to prepare the standard working solution freshly once a month. Storage of milk at 4 °C is suitable for some analytes (ABZ-SO, FBZ-SO2, FLUBZ, ABZ, ABZ-NH2-SO2) whereas for the muscle almost all substances were stable only at -20 °C. Some freeze-thaw and short-term stability changes were detected.

Lanthanide bimetallic MOF-based fluorescent sensor for sensitive and visual detection of sulfamerazine and malachite.

A lanthanide terbium/europium metal-organic framework (Tb0.6Eu0.4-MOF) was prepared by one-step solvothermal method at room temperature. A series of characterizations including scanning electron microscopy, powder X-ray diffraction spectra, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were carried out to clarify the physical characteristics of the synthesized material. The data clarified that the prepared Tb0.6Eu0.4-MOF possessed rod-like morphology with a width of 1-2 µm, and had good crystal structure, good stability, response speed and excitation-independent emission feature. The bunchy Tb0.6Eu0.4-MOF was then used to construct fluorescent sensors for rapid identification of malachite green and sulfamerazine. It was revealed that the detection mechanism was inner filter effect. The effects of different parameters such as excitation wavelength and incubation times were investigated on the fluorescence analysis performance. The data clarified that the optimal excitation wavelength and incubation time was 240 nm and 3 min, respectively. The detection platform exhibited the high sensitivity and selectivity toward malachite green in the linear range of 2-180 µM and determined limit of detection was 1.12 µM. Besides, the proposed sensor allowed sensitive detection of sulfamerazine in the linear range of 2-140 µM with a low detection limit of 0.1 µM. Meaningfully, a smartphone application was designed to assist the proposed sensor to realize visual, intelligent and rapid detection of malachite green and sulfamerazine. Furthermore, the practical application of the proposed sensor has been also verified by high performance liquid chromatography, showing good accuracy, sensitivity and satisfactory recoveries. The results suggested that the Tb0.6Eu0.4-MOF-based ratiometric fluorescent sensor had the potential to become a promising technique for rapid detection of malachite green or sulfamerazine with smartphone application. Therefore, the prepared Tb0.6Eu0.4-MOF is one kind of efficient and cost-effective potential materials for developing fluorescent sensor for rapid, sensitive and selective detection of sulfamerazine and malachite.

Ionophore coccidiostats - disposition kinetics in laying hens and residues transfer to eggs.

Poultry production is linked with the use of veterinary medicinal products to manage diseases. Ionophore coccidiostats have been permitted for use as feed additives within the European Union (EU) for the prevention of coccidiosis in various species of poultry with except of laying hens. The presence of chemical residues in eggs is a matter of major concern for consumers' health. Despite such prohibition of use in laying hens, they were identified as the most common non-target poultry species being frequently exposed to these class of coccidiostats. Many factors can influence the presence of residues in eggs. Carryover of these class of coccidiostat feed additives in the feed of laying hens has been identified as the main reason of their occurrence in commercial poultry eggs. The physicochemical properties of individual compounds, the physiology of the laying hen, and the biology of egg formation are believed to govern the residue transfer rate and its distribution between the egg white and yolk compartments. This paper reviews the causes of occurrence of residues of ionophore coccidiostats in eggs within the EU with special emphasis on their disposition kinetics in laying hens, and residue transfer into eggs. Additional effort was made to highlight future modeling perspectives on the potential application of pharmacokinetic modeling in predicting drug residue transfer and its concentration in eggs.

Monitoring results of veterinary drug residues in chicken and eggs in Xinjiang in 2019 - 2020 / 公共卫生与预防医学

Objective To know the residues of 13 veterinary drug residues in chicken and eggs foods in some areas in Xinjiang. Methods A total of 170 chicken and egg samples were randomly selected from supermarkets and farmers' markets in seven cities in Xinjiang. Eleven quinolone antibiotics, two tetracycline antibiotics, ribavirin and metronidazole were examined for veterinary drug residues using liquid chromatography tandem mass spectrometry (LC-MS/MS) . Results The overall detection rate of veterinary drug residues in eggs and chicken were 20%（18/90）and11.25%（9/80）. The overall over-standard rate were 18.89%（17/90）and 0（0/80）. Veterinary drug residues in chicken are heavier than eggs. Veterinary drugs were detected and over-standarded in all seven cities in Xinjiang monitored. Conclusion The veterinary drug contamination in chicken and eggs in Xinjiang is relatively serious. It is recommended to strengthen the standardization of production and supervision to ensure food safety.

Antibacterial Drug Residues in Small Ruminant Edible Tissues and Milk: A Literature Review of Commonly Used Medications in Small Ruminants.

This review provides a summary of extracted data from the published literature that contains drug residue depletion data for edible tissues and milk following treatment of sheep and goats. Out of 20,234 records obtained during the initial search, data from 177 records were included in this review. The data is separated by antibiotic class for ease of comparison between studies. Extracted data includes the active ingredient, dosing information, animal health status, analytical method and limits of detection, tolerance and maximum residue limit information, and time frames relative to residue absence or detection. This information is useful for understanding drug residue depletion profiles following extra-label use and for estimating withdrawal intervals, in order to protect the human food chain.

Phish-Pharm: A Searchable Database of Pharmacokinetics and Drug Residue Literature in Fish - 2022 Update.

A new version of Phish-Pharm: a Searchable Database of Pharmacokinetics and Drug Residue Literature in Fish has been updated and posted online at: http://www.fda.gov/AnimalVeterinary/ScienceResearch/ToolsResources/Phish-Pharm/default.htm . The new version contains over 700 articles encompassing 191 aquatic species (fish, shellfish, and more).Phish-Pharm, first released in 2005, accompanied an article in this Journal, titled "Fish Drug Analysis-Phish-Pharm: A Searchable Database of Pharmacokinetics Data in Fish," by R. Reimschuessel, L. Stewart, E. Squibb, K. Hirokawa, T. Brady, D. Brooks, B. Shaikh, C. Hodsdon, AAPS Journal. 2005;07(02):E288-E327, article 30. ( https://link.springer.com/article/10.1208/aapsj070230 )FDA understands that there are limited approved, conditionally approved, or indexed drugs available for use in aquatic animals. In response, FDA made this reference database publicly available to assist investigators in developing new animal drugs for aquatic species. The database also supports FDA Center for Veterinary Medicine's mission of protecting human and animal health by serving as a resource for the aquatic drug approval process and drug residue surveillance.Phish-Pharm is a Microsoft Access database that is periodically updated. Searchable fields include pharmacokinetic data and links to the abstract for each article. Phish-Pharm enables users to evaluate information on drugs and chemicals and to identify research gaps to guide future research. Phish-Pharm is not intended for aquaculture farmers to evaluate safety or effectiveness of unapproved drugs. Phish-Pharm is not an appropriate tool for recommending withdrawal intervals of drug and chemical residues due to variability among studies. Aquaculture farmers should only use approved, conditionally approved, or indexed drugs in their operations (see Approved Aquaculture Drugs ).

Comparison of florfenicol depletion in dairy goat milk using ultra-performance liquid chromatography with tandem mass spectrometry and a commercial on-farm test.

Florfenicol is a broad-spectrum antibiotic commonly prescribed in an extra-label manner for treating meat and dairy goats. Scientific data in support of a milk withdrawal interval recommendation is limited to plasma pharmacokinetic data and minimal milk residue data that is limited to cattle. Therefore, a rapid residue detection test (RRDT) could be a useful resource to determine if milk samples are free of drug residues and acceptable for sale. This study compared a commercially available RRDT (Charm® FLT strips) to detect florfenicol residues in fresh milk samples from healthy adult dairy breed goats treated with florfenicol (40 mg/kg subcutaneously twice 4 days apart) with quantitative analysis of florfenicol concentrations using ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS). In addition, storage claims for testing bovine milk using the RRDT were assessed using stored goat milk samples. Milk samples were collected every 12 h for a minimum of 26 days. Commercial RRDT strips remained positive in individual goats ranging from 528 to 792 h (22-33 days) after the second dose, whereas, UPLC-MS/MS indicated the last detectable florfenicol concentration in milk samples ranged from 504 to 720 h (21-30 days) after the second dose. Results from stored milk samples from treated goats indicate that samples can be stored for up to 5 days in the refrigerator and 60 days in the freezer after milking prior to being tested with a low risk of false-negative test results due to drug degradation. Elevated somatic cell counts and bacterial colony were noted in some of the milk samples in this study, but further study is required to understand the impact of these quality factors on RRDT results.

An Interactive Generic Physiologically Based Pharmacokinetic (igPBPK) Modeling Platform to Predict Drug Withdrawal Intervals in Cattle and Swine: A Case Study on Flunixin, Florfenicol, and Penicillin G.

Violative chemical residues in edible tissues from food-producing animals are of global public health concern. Great efforts have been made to develop physiologically based pharmacokinetic (PBPK) models for estimating withdrawal intervals (WDIs) for extralabel prescribed drugs in food animals. Existing models are insufficient to address the food safety concern as these models are either limited to 1 specific drug or difficult to be used by non-modelers. This study aimed to develop a user-friendly generic PBPK platform that can predict tissue residues and estimate WDIs for multiple drugs including flunixin, florfenicol, and penicillin G in cattle and swine. Mechanism-based in silico methods were used to predict tissue/plasma partition coefficients and the models were calibrated and evaluated with pharmacokinetic data from Food Animal Residue Avoidance Databank (FARAD). Results showed that model predictions were, in general, within a 2-fold factor of experimental data for all 3 drugs in both species. Following extralabel administration and respective U.S. FDA-approved tolerances, predicted WDIs for both cattle and swine were close to or slightly longer than FDA-approved label withdrawal times (eg, predicted 8, 28, and 7 days vs labeled 4, 28, and 4 days for flunixin, florfenicol, and penicillin G in cattle, respectively). The final model was converted to a web-based interactive generic PBPK platform. This PBPK platform serves as a user-friendly quantitative tool for real-time predictions of WDIs for flunixin, florfenicol, and penicillin G following FDA-approved label or extralabel use in both cattle and swine, and provides a basis for extrapolating to other drugs and species.

Generation and Characterization of an Anti-diclazuril Monoclonal Antibody and Development of a Diagnostic Enzyme-Linked Immunosorbent Assay for Poultry.

An anti-diclazuril monoclonal antibody (mAb) was developed for use in enzyme-linked immunosorbent assay (ELISA)-based detection of diclazuril with high sensitivity and specificity, which can be used to measure anti-coccidial drug residues. The anti-diclazuril mAb had a half-maximal inhibitory concentration of 0.449-0.517 ng/mL. The mAb cross-reactivity with toltrazuril, toltrazuril 18 sulfone, clozaril, monesin, madurmycin, and salinomycin was very minimal (< 0.1%). The detection limit of the ELISA using this mAb was 0.10 ng/mL and the sensitivity was 0.05 ng/mL. A standard curve generated in the range of 0.05-16.2 ng/mL had a linear correlation coefficient value of ≥ 0.99. The average recoveries of diclazuril from chicken and duck samples ranged from 85.0 to 102.5%.Intra- and inter-assay coefficients of variation ranged from 5.9 to 8.5% and 9.2 to 12.6%, respectively. Using the International Immunogenetics Information System®, the VH domain of the mAb was found to be encoded by an IGHV3 family gene and had the following complementarity determining region (CDR) sequences: GFTFSRY (CDR1), SRGGS (CDR2), and GDDNYAFAY (CDR3). The VL domain was encoded by an IGKV1 family gene and had the following CDR sequences: KSSQSLLNSRTRKNYLA (CDR1), WASTRES (CDR2), and KQSYNLHT (CDR3). This study provides a method to generate anti-diclazuril mAbs and determine their variable region sequences. The diagnostic ELISA developed using this mAb may drive additional studies on the monitoring and detection of food and veterinary drug residues.