Persistent residues: interface with regulatory decisions

The use of radiolabeled drugs and feed additives in experiments designed for preclearance approval of new animal drug applications (NADAs) demonstrates the presence of metabolites, including those which are covalently bound to macromolecules and which often persist in the edible tissues of target food animals. Isolation and characterization of these residues is often a difficult task. An outline of data development is explored in the context of toxicity assessment. Unless otherwise adjusted, the sponsor's method of residue analysis and drug withdrawal time reflect the influence of all related drug residues found in edible tissues. The use of bioavailability studies and their interaction with safety evaluation is discussed.