Drug residues in animal tissues and their regulatory significance--the Canadian point of view.

Today it is almost impossible to produce food of animal origin which is free from traces of drugs or chemicals. In Canada the problem of drug residues is controlled by a method of assessment of human safety which involves many factors. The toxicity of the drug in laboratory animals or, if possible, in man, is established and a no-effect dose is then estimated. These studies require oral administration of the drug and include acute, subacute, and teratogenicity studies. Depending on these results, chronic reproductive or carcinogenicity studies may be required before a no-effect dose can be estimated. Residue studies must encompass data on metabolism, pharmacokinetics, and depletion studies in edible tissues and for products such as milk and eggs. For veterinary drug residues, we must consider the target food animal with its particular metabolism, tissue disposition, and excretion patterns. The analytical method for residue detection must be acceptable and its sensitivity limits suitable for the drug and its major metabolites.