RESUMO
In order to monitor salbutamol (SAL) use in goats as a repartitioning, we determined SAL residues in various tissues of goats after repeated oral SAL administration at a dose of 0.15 mg/kg daily for 21 days. SAL concentrations were measured by ultra performance liquid chromatography tandem mass spectrometry in extracts of tissues from goats sacrificed 0.25, 1, 3, 7, 14, 21 and 28 days after the last dose. Our results showed that on Day 0.25 of the withdrawal period, the residual proportions of SAL (expressed as percentage) in liver, kidney, lung, hair, stomachs and muscle were 19.5%, 15.3%, 3.3%, 9.6%, 28.2% and 0.8%, respectively. As the withdrawal time increased, the SAL concentrations in most tissues (except hair) decreased rapidly over the first 3 days and more slowly in the following 25 days. After a 28-day withdrawal period, hair, lung, muscle, liver, fat, eyes, rumen, kidney and abomasum still contained ~32.3%, 15.3%, 7.1%, 6.5%, 5.6%, 1.5%, 0.8% and 0.5% compared to the initial residual concentrations determined on Day 0.25, respectively. On withdrawal Day 28, the highest concentrations of SAL were found in hair (16.58 ± 9.48 µg/kg), followed by liver (7.01 ± 0.94 µg/kg), lung (2.81 ± 1.23 µg/kg), kidney (0.64 ± 0.56 µg/kg), whereas the concentrations in other tissues were lower than limit of quantification (0.50 µg/kg). SAL residues were not detected in bile, plasma and brain on Days 7, 7 and 3 after discontinuation of dosing. These findings indicated that the distribution and depletion rates of SAL differed between tissues. It should be noted that SAL residues in stomach were higher than those in muscles during the early withdrawal. We conclude that hair is the preferred tissue to monitor the administration of SAL to living goats, whereas liver can be used to monitor SAL in the carcass for determination of compliance with food safety regulation.