This study was conducted to re-establish the withdrawal time (WT) for ivermectin (IVM) in pigs as part of the introduction of the positive list system (PLS) program. Forty-two healthy pigs were orally administered IVM at doses of 2.4 mg/kg feed (IVM-1, n = 20) and 4.8 mg/kg feed (IVM-2, n = 20) once daily for 7 days. After treatment, tissue samples were collected from four pigs at 1, 3, 5, 7, and 14 days post-administration. Based on a previously established analytical method, residual IVM concentrations in pig tissues were determined using LC-MS/MS. In the IVM-1 group, IVM levels in muscle, liver, kidney, and fat were below the limit of quantification (LOQ) on days 7, 7, 7, and 14 after the final administration, respectively. In the IVM-2 group, IVM levels in muscle, liver, kidney, and fat were below the LOQ on days 7, 14, 7, and 14 after the final administration, respectively. According to the European Medicines Agency guideline on the determination of withdrawal times, the WTs for IVM-1 and IVM-2 in edible pig tissues were established as 8 and 11 days, respectively. In conclusion, the estimated WT of IVM in swine edible tissues was shorter than the currently recommended WT of 14 days for IVM.

This study was conducted to re-establish the withdrawal time (WT) of ivermectin (IVM) in goats in accordance with the implementation of the positive list system (PLS). Thirty-four healthy goats were topically administered IVM at doses of 0.5 mg/kg body weight (BW) (IVM-1, n = 16) or 1.0 mg/kg BW (IVM-2, n = 16) as a single treatment. Tissue samples were collected from four goats at 3, 7, 14, and 28 days post-administration. Residual concentrations of IVM in edible tissues were determined using LC-MS/MS based on a previously validated analytical method. In the IVM-1 group, IVM concentrations in all edible tissues were below the limit of quantification (LOQ) by day 3 post-administration. In the IVM-2 group, IVM concentrations in muscle, liver, kidney, and fat were below the LOQ by days 7, 3, 3, and 7 post-administration, respectively. WTs were estimated in accordance with the European Medicines Agency guideline on the determination of withdrawal periods. The calculated WTs for IVM-1 and IVM-2 were 12 and 19 days, respectively. In conclusion, the estimated WT of IVM in edible goat tissues was shorter than the currently recommended withdrawal period of 28 days.