Even after health-based guidance values (HBGVs) are established, there are still many unknowns regarding the residues once the drug is administered into the target (food-producing) animal species. In which edible tissues will the drug residues be found? What specific residues will be found in the edible tissues? How much of each specific residue will occur? How long will the residues persist in edible tissues after the drug is administered?

Consult the guidance document on total residues for information on:

• the applications of radiolabelled drug residue depletion studies for determining total residues in edible tissues;
• the critical outcomes and limitations of total residue depletion studies contrasted with traditional (non-radiolabelled) residue depletion studies and the role of each in the broader residue assessment;
• the importance of identifying and characterizing specific residue components (metabolites) produced by the target species through radiolabelled residue depletion studies or other means; and
• relevant guidance documents for additional technical advice on the design and analysis of total residue depletion studies.