Comparative plasma and urine concentrations of flunixin and meloxicam in goats
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© 2019 Elsevier B.V. The objective of this study was to compare plasma and urine concentrations of flunixin and meloxicam, in order to determine withdrawal intervals for animals at livestock shows where urine is routinely tested. Eleven goats were housed in individual metabolism cages to facilitate complete urine collection. All animals were randomly divided into one of two treatment groups and received either a single dose of 2.2 mg/kg flunixin in the muscle (n = 5) or 0.5 mg/kg meloxicam by mouth (n = 6). Flunixin meglumine was given via an intramuscular injection to evaluate the effect of extra label administration on the disposition of flunixin in goats. The information from this study represents a potential worst-case scenario for urine depletion and helps determine the withdrawal intervals needed for flunixin meglumine in show goats when administered in this extra label manner. Plasma and urine samples were collected over 360 h and analyzed by tandem mass spectrometry (UPLC-MS-MS). Goats were euthanized at the end of the study, and liver samples were collected at necropsy 15 days post dose in order to quantify any potential residues. Drug levels in urine reached peak concentrations between 8 and 16 h after dosing for both drugs. Flunixin urine concentrations were higher than maximum levels determined in plasma. Urine concentrations for both flunixin and meloxicam fell below the limit of detection (LOD) of 1.0 ng/mL by 240 h in all goats. Calculated harmonic mean apparent elimination half-life in plasma based on non-compartmental analysis was 5.4 ± 0.001 h and 10.3 ± 0.001 h for flunixin and meloxicam respectively. Five of six liver samples for goats administered meloxicam fell below the limit of quantification (LOQ) of 5.0 ng/mL by 15 days. Four out of five liver samples for goats administered flunixin fell below the LOQ (5.0 ng/mL) by 15 days. Flunixin and meloxicam administered to healthy goats exhibited longer elimination from urine than plasma, but followed a similar and linear depletion profile. Urine concentrations did not correlate with liver residues. This study provides useful information that can assist livestock show authorities and veterinarians determine an appropriate withdrawal interval for show animals whose urine may be tested prior to competition.
author list (cited authors)
Bublitz, C. M., Mzyk, D. A., Mays, T., Fajt, V. R., Hairgrove, T., & Baynes, R. E.