Establishment of withdrawal time and analysis of amitraz residue in edible tissues of pigs following topical application

초록

This study was conducted to re-establish the withdrawal time for amitraz (AMT) in pigs in preparation for the implementation of the Positive List System (PLS). Thirty-two healthy pigs were randomly assigned to two groups and received a single topical application of AMT at concentrations of 1.0 mg/mL (AMT-1, n = 16) or 2.0 mg/mL (AMT-2, n = 16). A volume of 1 L of the respective formulation was sprayed onto the body surface of each animal. Tissue samples were collected from four pigs per group at 1, 3, 5, and 7 days post-treatment. Residual concentrations of AMT and its metabolite, 2,4-dimethylaniline, in porcine tissues were determined using a previously validated LC-MS/MS method. AMT residue levels were calculated as the sum of the measured concentrations of AMT and 2,4-dimethylaniline. In both the AMT-1 and AMT-2 groups, AMT concentrations in muscle, liver, and kidney tissues were below the limit of quantification (LOQ) from Day 1 onward. In the AMT-1 group, AMT residues remained above the LOQ in fat tissue through Day 1 and in skin tissue through Day 3. In the AMT-2 group, AMT residues remained above the LOQ in both fat and skin tissues through Day 7. According to the European Medicines Agency guideline on the determination of withdrawal periods, the withdrawal time for the AMT-1 group was estimated to be 4 days for skin, whereas those for the AMT-2 group were 2 days for fat and 4 days for skin. These findings suggest that the withdrawal period for AMT in edible porcine tissues may be shorter than the currently recommended withdrawal period of 7 days under certain application conditions.

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