Pharmacokinetics and tissue disposition of meloxicam in beef calves after repeated oral administration.

Abstract

The objective of this study was to investigate the pharmacokinetics and tissue disposition of meloxicam after repeated oral administration in calves. Thirteen male British×Continental beef calves aged 4 to 6months and weighing 297-392kg received 0.5mg/kg meloxicam per os once daily for 4days. Plasma meloxicam concentrations were determined in 8 calves over 6days after first treatment. Calves were randomly assigned to be euthanized at 5, 10, 15 (n=3/timepoint), and 19days (n=4) after final administration. Meloxicam concentrations were determined in plasma (LOQ= 0.025μg/mL) and muscle, liver, kidney, and fat samples (LOQ=2ng/g) after extraction using validated LC-MS-MS methods. The mean (± SD) Cmax , Cmin , and Caverage plasma meloxicam concentrations were 4.52±0.87μg/mL, 2.95±0.77 μg/mL, and 3.84±0.81μg/mL, respectively. Mean (± SD) tissue meloxicam concentrations were highest in liver (226.67±118.16ng/g) and kidney samples (52.73±39.01ng/g) at 5days after final treatment. Meloxicam concentrations were below the LOQ in all tissues at 15days after treatment. These findings suggest that tissue from meloxicam-treated calves will have low residue concentrations by 21days after repeated oral administration.