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This study describes the pharmacokinetics of topical and intravenous (IV) flunixin meglumine in Holstein calves. Eight male Holsteins calves, aged 6 to 8 weeks, were administered flunixin at a dose of 2.2 mg/kg intravenously. Following a 10-day washout period, calves were dosed with flunixin at 3.33 mg/kg topically (transdermal). Blood samples were collected at predetermined times from 0 to 48 h for the intravenous portions and 0 to 72 h following topical dosing. Plasma drug concentrations were determined using liquid chromatography with mass spectroscopy. Pharmacokinetic analysis was completed using noncompartmental methods. The mean bioavailability of topical flunixin was calculated to be 48%. The mean AUC for flunixin was determined to be 13.9 h × ug/mL for IV administration and 10.1 h × ug/mL for topical administration. The mean half-life for topical flunixin was 6.42 h and 4.99 h for the intravenous route. The C following topical application of flunixin was 1.17 μg/mL. The time to maximum concentration was 2.14 h. Mean residence time (MRT) following IV injection was 4.38 h and 8.36 h after topical administration. In conclusion, flunixin when administered as a topical preparation is rapidly absorbed and has longer half-life compared to IV administration.

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Cannabinoid production for medicinal purposes has renewed interest in utilizing byproducts of industrial hemp (IH) as a feed source for livestock. However, the presence of bioactive residues in animal tissues may pose a risk to consumers. The purpose of this study was to characterize the plasma pharmacokinetics (PK) of cannabinoids and their metabolites in cattle after a single oral exposure to IH. Eight castrated male Holstein calves received a single oral dose of 35 g of IH to achieve a target dose of 5.4 mg/kg cannabidiolic acid (CBDA). Blood samples were collected for 96 h after dosing. Plasma cannabinoid concentrations were profiled using liquid chromatography coupled with mass-spectroscopy (UPLC) and PK parameters were calculated using noncompartmental methods. The cannabinoids CBDA, tetrahydrocannabinolic acid-A (THCA-A), cannabidivarinic acid (CBDVA), and cannabichromenic acid (CBCA) were detected in all cattle after IH dosing. The geometric mean maximum concentration of CBDA of 72.7 ng/mL was observed at 14 h after administration. The geometric mean half-life of CBDA was 14.1 h. No changes in serum biochemistry analysis were observed following IH dosing compared to baseline values. These results show acidic cannabinoids, especially CBDA, are readily absorbed from the rumen and available for distribution throughout the body.

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