Diclofenac was responsible for the decimation of Gyps vulture species on the Indian subcontinent during the 1980s and 1990s. Gyps vultures are extremely sensitive (the lethal dose 50 [LD50] ~ 0.1 mg/kg - 0.2 mg/kg), with toxicity appearing to be linked to metabolic deficiency, demonstrated by the long T1/2 (~12 h - 17 h). This is in striking comparison to the domestic chicken (Gallus gallus domesticus), in which the LD50 is ~10 mg/kg and the T1/2 is ~1 h. The phase 1 cytochrome P450 (CYP) 2C subfamily has been cited as a possible reason for metabolic deficiency. The aim of this study was to determine if CYP2C9 homolog pharmacogenomic differences amongst avian species is driving diclofenac toxicity in Gyps vultures. We exposed each of 10 CYP-inhibited test group chickens to a unique dose of diclofenac (as per the Organisation for Economic Co-operation and Development [OECD] toxicity testing guidelines) and compared the toxicity and pharmacokinetic results to control group birds that received no CYP inhibitor. Although no differences were noted in the LD50 values for each group (11.92 mg/kg in the CYP-inhibited test group and 11.58 mg/kg in the control group), the pharmacokinetic profile of the test group was suggestive of partial inhibition of CYP metabolism. Evaluation of the metabolite peaks produced also suggested partial metabolic inhibition in test group birds, as they produced lower amounts of metabolites for one of the three peaks demonstrated and had higher diclofenac exposure. This pilot study supports the hypothesis that CYP metabolism is varied amongst bird species and may explain the higher resilience to diclofenac in the chicken versus vultures.

Introduction: Quercetin is a polyphenolic flavonoid which has been used in traditional Chinese medicine as a natural therapeutic agent with a broad spectrum of activities (antioxidant, anticancer, neuroprotective, anti-inflammatory, antiviral and antibacterial). The aim of this study was to develop and validate a rapid and simple ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method for the determination of quercetin in milk. Material and Methods: Sample preparation was based on a liquid-liquid extraction with 0.5% formic acid in acetonitrile. The chromatographic separation was performed on a ZORBAX SB-C18 column with methanol and 0.5% formic acid as a mobile phase. Results: The procedure was successfully validated. The mean recovery of the analyte was 98%, with the corresponding intra- and inter-day variation less than 10% and 15%, respectively, and the repeatability and reproducibility were in the range of 3%–7.2% and 6.1%–12%, respectively. The lowest level of quantification was 1.0 μg/kg. Conclusion: The proposed method was successfully applied in evaluating the pharmacokinetics of quercetin in milk obtained from dairy cows with clinical mastitis after intramammary administration.

Introduction: Quercetin is a polyphenolic flavonoid which has been used in traditional Chinese medicine as a natural therapeutic agent with a broad spectrum of activities (antioxidant, anticancer, neuroprotective, anti-inflammatory, antiviral and antibacterial). The aim of this study was to develop and validate a rapid and simple ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method for the determination of quercetin in milk.

Introduction: There are many veterinary products containing β-lactam antibiotics which are used for mastitis treatment in cows. The aim of the study was to determine whether mastitis could have any effect on amoxicillin (AMX) or penicillin G procaine (PEN) withdrawal period from milk, in the context of current maximum residue limits established by the European Commission. Material and Methods: The study was conducted on 17 dairy Black and White cows with clinical mastitis during the lactation period. The first group (n = 8) received 200 mg of amoxicillin (AMX), whereas the second group (n = 9) received 200,000 IU/mg of penicillin G procaine (PEN) by intramammary administration. For the measurement of AMX and PEN concentrations in milk, the liquid chromatography tandem mass spectrometry method was applied. Pharmacokinetic calculations were performed using Phoenix WinNonlin 6.4 software. Results: The determined AMX and PEN half-life values in the mammary gland suggest that the drug withdrawal is at a level of 99.9% within 81 h (≈3.5 days) and 116 h (≈5 days) after administration of AMX and PEN, respectively. The present research indicates that, at 60 h after administration, the average PEN concentration in the milk from cows with clinical signs of mastitis may still reach 4.96 g/kg and that of AMX can even be 6.92 g/kg. Conclusion: The results obtained confirm that, in mastitis cases, a 72-h withdrawal period is sufficient for elimination of AMX to a lower level than the established maximum residue limit (MRL) values. However, in the case of PEN, at 69 h after administration, the drug concentration may be close to that of the determined MRL.

Introduction: The objective of this study was to describe a pharmacokinetic–pharmacodynamic (PK/PD) approach for determination of a rational dosage of ampicillin (AMP) and depletion of the antibiotic residues in milk after intramammary administration to cows.Material and Methods: The cows came from different farms from the Lublin Province area. They (n = 9) received 5 g of the drug, containing 75 mg of AMP sodium in physiological solution, through a syringe tube by intramammary administration. Following single intramammary administration, the milk samples (5 mL) were collected after 2, 4, 6, 8, 10, 24, 36, 48, and 60 h. The liquid chromatography-mass spectrometry analysis was performed on the Agilent 1200 system connected to an AB Sciex API 4000™ mass spectrometer. The pharmacokinetic analysis of the concentrations of the antibiotic in milk was performed using software Phoenix® WinNonlin® 6.4. Calculations were made in non-compartmental (slopes, highest, amounts, and moments) and compartmental analysis.Results: The pharmacokinetic characteristics of AMP after intramammary administration indicate rapid elimination of the drug from milk. The mean residence time had a several-fold lower value than the designated elimination half-life and amounts to only 3.4 h. The concentration of the drug in the milk dropped relatively quickly and the process was very dynamic.Conclusion: The conducted research confirms the rationale of using the PK/PD model in order to verify the dosing regimen for other antibiotic groups and various indicators of the applied PK/PD model.

Introduction: There are many veterinary products containing β-lactam antibiotics which are used for mastitis treatment in cows. The aim of the study was to determine whether mastitis could have any effect on amoxicillin (AMX) or penicillin G procaine (PEN) withdrawal period from milk, in the context of current maximum residue limits established by the European Commission.

Enrofloxacin (ENR) is a wide broad-spectrum antibacterial drug used widely in veterinary medicine. It was aimed to investigate the pharmacokinetic behavior of ENR in Kilis goats at single dosage of 2.5 mg/kg per goat body weight (bw) in the present study. A total of 10 healthy Kilis male goats were divided into 2 groups: each including 5 animals for the pharmacokinetic studies Group I, received 2.5 mg/kg via vena jugularis by IV route; Group 2 received the same dose by intramuscular route through administration at musculus semitendinosus at formulation. Group 1 blood samples were taken at 0.08, 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 8, 12, 18, 24, 36 and 48 hours and Group 2 blood samples were taken at 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 8, 12, 18, 24, 36 and 48 hours after administration of drug. ENR and its metabolite, ciprofloxacin (CPR) analysis was performed by high-performance liquid chromatography. Maximal plasma concentration (Cmax 0.77 ± 0.05 μg/ml for IM) was reached at 1.00 h (Tmax) for IM. The elimination half-life (T1/2) of ENR was of 21.09 ± 0.87 h for IV and 29.75 ± 2.50 h for IM. The values of area under concentration-time curve (AUC) of ENR were of 6.46 ± 0.52 and 4.11 ± 0.35 μg.h/ml. ENR bioavailability (F) was calculated as 63.62%. The elimination half-life of CPR was of 19.31 ± 2.15 h for IV and 33.42 ± 1.28 h for IM.

Chlortetracycline (CTC) is a broad-spectrum antibiotic belonging to the tetracycline group of drugs. It is commonly used in the poultry industry for the treatment of bacterial infections and is also used as a growth promoter. This study was aimed at validating the sensitive HPLC method for the assay of CTC in chicken plasma. The method consisted of isocratic elution with separation using a C]8 column. The mobile phase used in the study was aqueous oxalic acid (0.03M), acetonitrile and methanol in the ratio of 60:30:10. The HPLC conditions included a flow rate of Iml/min with UVdetection at 375nm. CTC in chicken plasma was extracted with Mcllvaine buffer followed by dilution with water in the ratio of 1:1 andfiltered using 0.22p filters. The peak of chlortetracycline was noticed at 5-6 minis. The method was linear from 0.05mg/ml to 10mg/ml. The recovery percentage from plasma was recorded as 110%. Thus, from this study it is inferred that this method is optimal for the assay of CTC in plasma for pharmacokinetic studies.

Ceftizoxime is the third generation cephalosporin, extensively used in veterinary medicine. It has larger volume of distribution, good penetration into tissues, and useful for the treatment of mastitis which is resistant to other antibiotics. Keeping in view of generating pharmacokinetic data of ceftizoxime in different domestic animals, the present study was planned to investigate pharmacokinetics of ceftizoxime in goats (n = 6) at the dose rate of 10mg kg-1 body weight following single dose intravenous administration. Drug concentration in plasma was determined using High Performance Liquid Chromatography (HPLC) with UV detector. The values of Cmax, AUC and MRT were 44.40 ± 2.09 µg ml-1, 121.22 ± 15.40µg.h.ml-1 and 11.44 ± 1.30 h, respectively. The longer elimination half-life (8.92 ± 1.11h) along with smaller ClB (0.09 ± 0.01 Lh-1 kg-1) showed slower excretion of the drug from animal body. 

OBJECTIVE To characterize the pharmacokinetics of mycophenolate mofetil (MMF) following single-dose IV or PO administration, characterize the pharmacokinetics of MMF following long-term PO administration, and describe the clinicopathologic effects of long-term MMF administration in horses. ANIMALS 12 healthy adult horses. PROCEDURES In phase 1, 6 horses received a single IV (2.5 mg/kg) or PO (5 mg/kg) dose of MMF in a randomized balanced crossover assessment (≥ 2-week interval between administrations). In phase 2, 6 other horses received MMF for 60 days (5 mg/kg, PO, q 24 h for 30 days and then 5 mg/kg, PO, q 48 h for an additional 30 days). RESULTS Following IV (single-dose) or PO (single- or multiple-dose) administration, MMF was rapidly converted to mycophenolic acid. For single-dose PO administration, mean ± SD maximum plasma mycophenolic acid concentration was 1,778.3 ± 441.5 ng/mL at 0.71 ± 0.29 hours. For single-dose IV administration, mean systemic clearance and volume of distribution at steady state were 0.689 ± 0.194 L/h/kg and 1.57 ± 0.626 L/kg, respectively. Following single doses, mean terminal half-life was 3.99 ± 0.865 hours for IV administration and 4.02 ± 1.01 hours for PO administration. The accumulation index following long-term PO administration was 1.0 ± 0.002, and the terminal half-life was 4.59 ± 1.25 hours following the final dose on day 60. None of the horses developed abnormal clinical signs or had any consistently abnormal clinicopathologic findings. CONCLUSIONS AND CLINICAL RELEVANCE Further investigation of the clinical efficacy of long-term MMF treatment of horses with autoimmune diseases is warranted.