An introduction to principles of veterinary clinical pharmacology: the elimination of drugs. 2. Mechanisms of drug elimination

Authors: Baggot JD
Publication: New Zealand Veterinary Journal, Volume 22, Issue 5, pp 63-71, May 1974
Publisher: Taylor and Francis

Animal type: Livestock
Subject Terms: Metabolic disease, Pharmacology
Article class: Review Article

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Abstract: Drug elimination refers to all processes that operate to reduce the effective concentration of drug in the body fluids. Metabolism, storage and excretion are the three mechanisms whereby drugs are ultimately removed from their sites of action. Most drugs undergo metabolic transformation in the body i.e., biotransformation to more polar products with diminished or no activity. The principal site of drug biotransformation is the liver. However, biotransformation may also take place to varying extents in other tissues, including the intestinal mucosa, the blood plasma and the renal epithelium, and by the action of gut microflora. The most common pathways of drug metabolism involve oxidation, reduction, hydrolysis and conjugation. Very often a drug is subjected to several competing pathways simultaneously, and the extent of formation of the various metabolites depends on the relative rates of the various metabolic processes. In addition, metabolic reactions frequently proceed sequentially; oxidation, reduction, or hydrolysis reactions are followed by conjugation of products of the initial reaction. Numerous factors may influence the metabolism and, consequently, the activity of a chemical agent…

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