PRECLINICAL DRUG-METABOLISM PROGRAMS FOR FOOD-PRODUCING ANIMALS

To register a new veterinary drug for use in food-producing animals, t he sponsor must demonstrate that drug-related residues in the edible t issues (liver, kidneys, muscle, fat, and milk or eggs) of treated anim als are safe when consumed by humans. The sponsor must develop informa tion on the amount, persistence, and chemical nature of the drug-deriv ed residue in the edible tissues in order to ensure safety. This infor mation is compared to that on the metabolism and toxicity of the compo und in the laboratory animal species used for the toxicity evaluation. The toxicity data is utilized to establish the safe concentration of drug-related residue in the edible tissues. An estimate of the safe co ncentration is necessary to proceed with residue studies that will ade quately determine the rate of depletion of total residue over the proj ected range of probable safe concentrations. Appropriate study design requires close communication among the toxicologist, pathologist, and residue chemist. The safe concentration of total residue and residue d epletion profile are used to determine the withdrawal period for the v eterinary product. The required studies, including design and timing, will be discussed.