Veterinary drug residues

This chapter will review the way in which veterinary pharmaceutical drugs are used and the controls placed on their use. It will also explain how information from veterinary drug residues surveillance programmes coupled with knowledge of the potential risk they pose can be used to assess the hazards they may present if allowed to enter the human food chain. 

The development of human pharmaceutical medicines has progressed significantly over the last twenty-five years. This has also been accompanied by a similar expansion in the development and range of pharmaceutical products available to the veterinary profession for the treatment and control of animal diseases. As with human medicines, veterinary medicines have to undergo extensive evaluation for efficacy and safety (target species, operator and consumer) to ensure that they are both effective and safe to use. The residues of these drugs that may be present in edible tissues, for some time following treatment, are of concern for those involved in consumer protection. 

As intensified animal production continues to increase, the genetic selection of animals more suited to these production systems together with the prophylactic use of drugs as a precaution against infection has also increased. In particular with the intensification of poultry meat and pig meat production systems where there is a high risk of infection that can be rapidly transmitted, drugs are often administered as a preventative measure. 

Pharmaceutical companies wishing to register new products must submit a dossier of data, relating to trials and investigations on the product, to MAFF. When MAFF (VMD) is satisfied that the data are complete and the research has been properly conducted to internationally accepted standards of competence (Good Laboratory Practice - GLP), the dossiers are passed to the VPC. The VPC then assesses the quality, efficacy and safety of the product. The safety assessment on the product includes the target species, human (operator, consumer) and environmental impact. If there are any substantial doubts, the licence may be refused and/or the company advised to carry out further investigations. 

In addressing consumer safety the VPC achieves this by consideration of the toxicological data and the no effect level (NEL = No observed Effect Level) for that substance in experimental animals. This, together with an additional safety factor to allow for any inter-species and intra-species variability, is used to calculate the acceptable daily intake (ADI). For an adult human the ADI is calculated from the NEL by using the following formula for a 60 kg person  

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R. J. Heitzman, Veterinary Drug Residues. Residues in Food Producing Animals and their Products Reference Materials and Methods, Final Report EUR 14126EN, Office for Official Publications of the European Communities Luxembourg, 1992. 

Toxic compounds polychlorinated biphenyls, polycyclic aromatic hydrocarbons, organochlorine pesticides, chlorinated pesticides, dioxins, veterinary drug residues, hormone residues, aflatoxins, toxic compounds in shellfish. Compoimds of nutritional significance in foods vitamins, fat, lipids, carbohydrates, protein, energy-calorific value, proximates, dietary fibre, ash. Other compounds hormones in blood serum... 

N. Haagsma and C. van der Water, Immunochemical methods in the analysis of veterinary drug residues, in Analysis of Antibiotic Drug Residues in Food Products of Animal Origin, ed. V. K. Agarwal, Plenum Press, New York, pp. 81-97 (1992). 

S.F. Sundlof and J. Cooper, Human health risks associated with drug residues in animal-derived foods, in Veterinary Drug Residues, Food Safety, ed. W.A. Moats and M.B. Medina, American Chemical Society, Washington, DC, pp. 5-17 (1996). 

Ryan, J.J. and H.A. McLeod. 1979. Chemical methods for the analysis of veterinary drug residues in foods. Part I. Residue Rev. 71 1-82. 

Natural toxins including fungal toxins chemical migration from packaging veterinary drug residues. 

Quan, D.J. (2000). Monitoring of domestic and imported eggs for veterinary drug residues by the Canadian food inspection agency, J. Agric. Food Chem., 48, 6421-6427. 

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) was established in 1955 to consider chemical, toxicological, and other aspects of contaminants and residues of veterinary drugs in foods for human consumption. The Codex Committee on Food Additives and Contaminants and the Codex Committee on Residues of Veterinary Dmgs in Foods identify food additives, contaminants, and veterinary drug residues that should receive priority evaluation and refer them to JECFA for assessment before incorporating them into Codex standards. 

World Health Organization, in Evaluation of Certain Veterinary Drug Residues in Food. Thirty-eighth Report of the Joint FAO/WHO Expert Committee on Food Additives, Technical Report Series 815, World Health Organization, Geneva (1991). 

Development of standards, guidelines, and recommendations for veterinary drug residues in food has been delegated by CAC to its subsidiary body, the Codex Committee on Residues of Veterinary Drugs in Foods (CCRVDF), which is more routinely involved in risk management. The work of this subcommittee is mainly supported by tire Joint FAOAVHO Expert Committee on Food Additives (JECFA). 

JECFA is a scientific advisory body established in tire 1950s, prior to the establishment of the CAC. Over the past 40 years, it has provided independent scientific advice to all FAO and WHO member countries. The traditional and current activities of JECFA are mainly in the area of risk assessment, not risk management. To some extent, however, JECFA activities also touch on risk management. Risk assessment, risk management, and risk communication constitute the three basic elements of risk analysis that are taken into account in the Codex procedure for setting MRLs of veterinary drug residues in foods (Table 11.1). 

Risk assessment, a process used to evaluate potential adverse effects on health from human exposure to veterinary drug residues, involves four stages starting from hazard identification and terminating through the hazard characterization and exposure assessment stages to risk characterization. 

In the exposure assessment stage, qualitative and quantitative evaluation of the likely intake of drug residues through food as well as exposure from other sources are performed. Estimating consumer exposure is based on the daily consumption of a particular food commodity combined with its content of veterinary drug residues. 

According to Directive 86/469/EEC of 16 September, 1986 (49), and its amendments, each Member State is required to test for the presence of antibiotics and other veterinary drug residues in edible animal products. Under the EU Annual National Plan (ANP) program, each Member State has to submit every year to the Commission a monitoring plan taking into account the specific national situation and setting out the national measures to be taken. The Commission examines the plans communicated by Member States to determine if they conform to the provisions laid down by Directive 86/469/EEC. 

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