The human food safety evaluation of veterinary drug residues helps ensure that food derived from treated food-producing animals is safe for human consumption. As part of the data collection process, studies should be conducted to permit an assessment of the quantity and nature of residues in food derived from animals treated with a veterinary drug. These metabolism studies provide data on (1) the depletion of residues of concern from edible tissues of treated animals at varying times after drug administration, (2) the individual components, or residues, that comprise the residue of concern in edible tissues, (3) the residue(s) that can serve as a marker for analytical methods intended for compliance purposes (i.e., monitoring of appropriate drug use), and (4) the identification of a target tissue or tissues, as applicable to national or regional programs.

Metabolism studies in food-producing animals most often are accomplished using radiolabeled drugs. These studies are sometimes referred to as total residue studies because they are capable of monitoring all (i.e., “total”) drug-derived residues resulting from the administration of test material. This guidance recommends procedures for metabolism studies conducted with radiolabeled drugs, when such studies are performed.

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