Regulatory authorities need to monitor for residues of veterinary drugs in food. Monitoring laboratories cannot easily quantify “total” drug residues. To detect total residues, the monitoring laboratory would need assays that detect and quantify all residue components (i.e. every metabolite). Rather than attempting to monitor total residues in food, the regulatory agencies instead monitor for a marker residue (MR).

Consult the guidance document to learn about:

 

• the characteristics of a suitable MR with examples for different types of MRs;
• the relationship between marker residues and total residues, particularly how the ratio of marker to total (M:T) residues varies between edible tissues and over time; and

alternative approaches to total residue assessment, such as the residue of concern (RoC) and related concepts like bioavailability and bioaccessibility.