The administration of veterinary medicinal products containing tiamulin hydrogen fumarate (THF) leads to the appearance of the following residues in animal tissues: THF and metabolites that can be hydrolyzed to 8-α-hydroxymutilin. The marker residue for tiamulin, according to Regulation EEC 2377/90, is the sum of the metabolites that can be hydrolyzed to 8-α-hydroxymutilin. The main aim of this study was to analyze the depletion of tiamulin residues and metabolites that can be hydrolyzed to 8-α-hydroxymulinin by liquid chromatography with tandem mass spectrometry (LC-MS/MS) in pig, rabbit and bird tissues after tiamulin administration and to determine minimum withdrawal times for products of animal origin intended for human consumption. Tiamulin was administered orally as follows: 12,000 µg/kg body weight/day for 7 days to pigs and rabbits and 20,000 µg tiamulin/kg body weight/day for 7 days to broiler chickens and turkeys. The values found for tiamulin marker residues were 3 times higher in liver than in muscle in pigs, 6 times in rabbits and 8–10 times in birds. The content of tiamulin residues in eggs from laying hens was below 1000 µg/kg at all times of analysis. The minimum withdrawal times for animal products intended for human consumption, resulting from this study, are 5 days for pigs, rabbits and turkeys, 3 days for broiler chickens and 0 days for eggs.

In this paper, we set the waiting time for the elimination of levamisole residues at a safe level from tissues (muscles and organs) from animals treated with levamisole 10%—oral solution. We studied the depletion of levamisole residues by high performance liquid chromatography with a mass spectrometer (limit of quantification 2 μg/kg) in the tissues of bovine, ovine, caprine, porcine and poultry (chickens and pigeons) after administration of levamisole (10 mg levamisole/kg body weight for cattle, sheep, goats, pigs and 20 mg levamisole/kg body weight for birds). We found that in cattle, sheep and goats at 7 days after treatment, the residues of levamisole in the liver and at 14 days and in the other tissues were below the established limit value. In pigs at 7 days, residues from all tissues were below the set limit value. Residue depletion in chickens treated with levamisole was rapid, such that 3 days after treatment, the residues in all tissues were below the set limit. Residue depletion was slower in turkeys than in chickens.