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

• Published in: Food and chemical toxicology 2023-11, Vol.181, p.114098-114098, Article 114098
• Main Authors: Wu, Xue, Lin, Zhoumeng, Toney, Emily, Clapham, Maaike O., Wetzlich, Scott E., Davis, Jennifer L., Chen, Qiran, Tell, Lisa A.
• Format: Article
• Language: English
• Subjects: antibiotics; Drug residue; Florfenicol; food safety; Goats; half life; kidneys; liver; maximum residue limits; Pharmacokinetics; Residue depletion kinetics; safety assessment; subcutaneous injection; Withdrawal time
• ISSN: 0278-6915; 1873-6351
• DOI: 10.1016/j.fct.2023.114098

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. •Pharmacokinetics and tissue residue depletion of florfenicol were studied in goats.•Goats received 40 mg/kg florfenicol via subcutaneous injections twice 96 h apart.•Plasma half-life was 101.80 h for florfenicol and 207.69 h for florfenicol amine.•Withdrawal intervals were 202 and 101 days for liver and kidney using FDA tolerance limit method.•The results help derive extralabel withdrawal intervals of florfenicol in goats.