Pharmacokinetic Parameters and Estimating Extra-Label Tissue Withdrawal Intervals Using Three Approaches and Various Matrices for Domestic Laying Chickens Following Meloxicam Administration

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.

Egg residue and depletion of meloxicam in Jing Hong laying hens following multiple oral doses

Meloxicam is a nonsteroidal anti-inflammatory drug (NSAID) commonly used in an extra-label manner in commercial laying hens for the treatment of foot lesions, which are a common issue in this species. The present study aimed to determine the depletion profiles of meloxicam in eggs with multiple oral administration under 2 different dosing regimens and to further recommend reasonable withdrawal intervals (WDIs). Meloxicam (1 mg/kg) was administered orally to laying hens under 2 dosing schedules: 10 doses at 24-h intervals and 15 doses at 12-h intervals. Eggs were collected daily after the first dosing, and meloxicam concentrations in both yolk and white were determined by a high-performance liquid chromatography (HPLC) method. The weight ratio of white to yolk in the whole egg was 1.54 (the mean of 20 eggs with repeated tests), and this value combined with the meloxicam concentrations in white and yolk were used to calculate the drug concentrations in whole eggs. Meloxicam was quickly eliminated from egg white, and its concentrations could only be quantified at 2 time points during the elimination phase. The elimination half-lives in yolk and whole egg were 3.07 ± 1.00 and 2.98 ± 0.88 d, respectively, after 10 repeated doses. And the corresponding elimination half-lives were 2.30 ± 0.83 and 2.18 ± 0.67 d, respectively, after repeated 15 doses. Considering the time when meloxicam was not detectable in eggs with the time of ovum development and maturation, a withdrawal interval (WDI) was suggested as 17 d for both dosing schedules. The current results enriched the study on the residue of meloxicam in domestic Jing Hong laying hens and provided WDIs to help ensure animal-derived food safety.

Pharmacokinetics of meloxicam in laying hens after single intravenous, oral, and intramuscular administration

The objective of this study was to determine the pharmacokinetics of meloxicam after a single intravenous (IV), intramuscular (IM), and oral (PO) dose at 1 mg/kg body weight in Jing Hong laying hens. Blood samples were collected at predetermined time points. Plasma meloxicam concentrations were determined using a validated high-performance liquid chromatography (HPLC) assay method and then subjected to a non-compartmental analysis. After IV administration, meloxicam had a mean (±SD) volume of distribution at steady-state (Vd_ss ) of 206.50 ± 25.23 ml/kg, a terminal half-life (t_1/2λ ) of 5.45 ± 0.53 h, and a total body clearance (Cl) of 26.48 ± 4.13 ml/h/kg. After PO and IM administration, meloxicam was absorbed relatively rapidly: the peak concentrations (C_max s) of 3.04 ± 0.56 and 8.94 ± 2.31 μg/ml were observed at 3.08 and 0.80 h, respectively. After PO and IM administration, the absolute bioavailability (F) was determined as 70.13% and 125.50%, respectively. Assuming that hens shared the same analgesic threshold of meloxicam (0.5 μg/ml) with humans, the plasma concentrations after three different routes (PO, IM, and IV) of administration were above this value for 16.7, 19.2, and 14.9 h, respectively.

Residue depletion profiles and withdrawal interval estimations of meloxicam in eggs and ovarian follicles following intravenous (Meloxicam solution for injection) and oral (Meloxidyl®) administration in domestic chickens (Gallus domesticus)

Meloxicam is a non-steroidal anti-inflammatory drug (NSAID) commonly prescribed in an extralabel manner for treating chickens in urbanized settings. The objectives of this study were to determine meloxicam depletion profiles in eggs and ovarian follicles and to estimate associated withdrawal intervals (WDI) in laying hens following a single intravenous or repeated oral administration. The observed peak concentration of meloxicam in ovarian follicles were consistently higher than in egg yolk and egg white samples. Terminal half-lives were 31-h, 113-h and 12-h in ovarian follicles, egg yolk and egg white samples, respectively, for repeated oral administrations at 1 mg/kg for 20 doses at 12-h intervals. The terminal half-life following a single intravenous administration at 1 mg/kg was 50-h for ovarian follicles. Meloxicam WDI estimations using ovarian follicle and egg yolk concentration data following 20 doses at 12-h intervals were 36 and 12 days, respectively. Meloxicam WDI estimation using egg yolk concentration data following 8 doses at 24-h intervals was 12 days. These results improve our understanding on the residue depletion of meloxicam from chickens' reproductive tracts and egg products and provide WDIs to help ensure food safety for humans consuming eggs from treated laying hens.