Radiolabelled Food Animal Depletion Research for Food Safety Standards-Setting; Associated Radioisotope Production and Radiosynthesis

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The demand for research to study and evaluate the metabolism and residue depletion kinetics of a priority list of veterinary drugs used in food-producing animals continues among several IAEA Member States. This is due to lack of scientific data needed to facilitate the setting of internationally harmonized and acceptable standards, commonly referred to as maximum residue levels (MRLs). These are to ensure good production practices and address pertinent public health and trade bottlenecks. Depletion studies require the use of radiolabelled drugs (or pesticides). These are either commercially procured or, where capacity exists, locally produced. In both cases, radioisotopes are needed. Setting MRLs in Member States at an international level requires data sets, including residue depletion to facilitate risk assessment by JECFA. The depletion rates are estimated using radiolabelled drugs in target animals. Such data is lacking for many Member States and there is an urgent need to address the gap and facilitate developing dossiers and JECFA evaluations.
Due to urgent calls by several developing country Member States, supported by a number of developed countries, the 24th Codex Committee for Residues of Veterinary Drugs (CCRVDF) in foods in May 2018 (FAO/WHO, 2018) identified nearly 300 compounds for which MRLs are needed but data is missing. Some of those to start with included (but not limited to): a) Amoxicillin in goats, poultry; b) Ampicillin in cattle, pig, horse, goats, sheep, fish, poultry; c) trypanocides e.g. Diminazene in sheep, goats; d) Imidocarb in horse; Ivermectin in horse, goats, camel, poultry; e) Oxytetracyline in honey, camel, horse, and goats. An IAEA CRP was initiated to contribute solutions to this research gap. However, the list is long and further research through a follow-up CRP is required. A lesson learned from the previous CRP is the challenge of accessing radioisotopes and radiolabelled drugs/pesticides for use in depletion studies. While commercial sources remain a predominant alternative, albeit often costly, scientists are exploring inhouse production of radioisotopes and using them to label drugs and subsequently apply them in depletion studies.
?Fazeali et al., (2024) produced Zinc-62/65 radioisotope at a local cyclotron, used it to label amoxicillin and subsequently used the labelled (65Zn-Amoxicillin) for depletion studies in rainbow trout fish. Related work is reported in the IAEA Nuclear Technology Review, 2025. Research studies on metabolism of veterinary drugs help identify and quantify the nature of the residues (VICH, 2012) and such evaluation ensures that food from animals treated with veterinary pharmaceuticals is safe for consumers. These studies generate data for instance on: (1) total residues (2) the depletion of drug residues from edible tissues at varying time intervals following administration, (3) metabolic profile, detailed understanding of the individual components/residues of concern, (4) marker residue(s) for compliance/regulatory purposes and monitoring of appropriate drug used, and (5) identification of target tissue (s) relevant to national or regional monitoring/regulatory programs (VICH, 2012).
The studies in food-producing animals require use of radiolabelled drugs which are rare among developing Member States, who thus depend largely on others or entirely on the private sector. The main objective of the CRP titled “Radiolabelled Food Animal Depletion Research for Food Safety Standards’-Setting; Associated Radioisotope Production and Radiosynthesis” is to support food safety standards-setting in Member States through use of innovative radiolabelled studies and radiometric analysis in food animals. The specific objectives are to: (1) To produce radioisotopes (by institute directly related to food safety laboratory) to be used in targeted radiolabelled food animal depletion studies that support standards-setting processes;? (2) radiolabel/radio synthesize selected veterinary pharmaceuticals and related substances by facilities adherent to food safety labs?to facilitate targeted food animal depletion studies; (3) conduct radiolabelled-based and complementary animal studies for veterinary pharmaceuticals and associated pesticides (dual-purpose use) substance (4) develop/validate or implement fit-for-purpose analytical method (5) report and disseminate research findings.
?The CRP will facilitate institutions in Member States to innovatively conduct food animal depletion studies using radioisotopes and explore the possibility of local/in-house production of the radioisotopes as well as their use to label the chemicals needed for the research.? It is in line with the Food Safety and Control sub-programme objective 2.1.3: to improve food safety and food control systems, specifically under the project 2.1.3.002 Assurance of food safety, quality and authenticity to enhance trade and relates to a concluding CRP D52043 on ‘Depletion of Veterinary Pharmaceuticals and Analysis of their Residues in Animal Matrices’. National or internationally permitted/recommended levels influence trade in food stuff and those set by the Codex Alimentarius Commission (international food code) serve as a reference point for the WTO. The project will focus on enhancing research capabilities and production of scientifically reliable information in Member States in the area of veterinary pharmaceuticals and determining residues of these substances in food producing animals. It will help Member States to provide data to Joint Expert Committee (of the FAO/WHO) on Food Additives (JECFA) for risk assessment and subsequent establishment for MRLs.
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