Disposition of Toxicants

This chapter deals with the study of absorption, distribution, metabolism/biotransformation, and excretion (ADME) of xenobiotics and the study of toxicokinetics of toxicants/xenobiotics in relation to time in animals. The disposition of a chemical determines its concentration at the site of action such that the concerted actions of absorption, distribution, and elimination also determine the potential for adverse events to occur. Metabolism or biotransformation of toxicants by the body is an “attempt to detoxify.” There are two phases of metabolism. Phase I includes oxidation, reduction, and hydrolysis mechanisms. These reactions, catalyzed by hepatic enzymes, generally convert foreign compounds to derivatives for Phase II reactions. This chapter briefly focuses on the overview, key points, and relevant text that are in the format of problem-solving study questions followed by multiple-choice questions (MCQs) along with their answers.

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Further Reading

• Fruncillo RJ (2011) 2,000 Toxicology board review questions. Xlibris, Publishers, Bloomington Google Scholar
• Gupta PK (2010) Absorption, distribution, & excretion of xenobiotics. In: Gupta PK (ed) Modern toxicology: basis of organ and reproduction toxicity, vol 1, 2nd reprint edn. PharmaMed Press, Hyderabad, pp 71–92 Google Scholar
• Gupta PK (2014) Essential concept in toxicology, 1st edn. BSP, Hyderabad Google Scholar
• Gupta PK (2016) Fundamental of toxicology: essential concept and applications. Elsevier/BSP, San Diego Google Scholar
• Gupta PK (2018) Illustrative toxicology, 1st edn. Elsevier, San Diego Google Scholar
• Gupta PK (2019) Concepts and applications in veterinary toxicology: an interactive guide. Springer-Nature, Switzerland BookGoogle Scholar
• Gupta PK (2020) Brain storming questions in toxicology. Francis and Taylor CRC Press, Boca Raton BookGoogle Scholar
• Krishnamurti CR (2010) Biotransformation of xenobiotics. In: Gupta PK (ed) Modern toxicology: basis of organ and reproduction toxicity, vol 1, 2nd reprint edn. PharmaMed Press, Hyderabad, pp 95–129 Google Scholar
• Lehman-McKeeman LD (2015) Absorption, distribution, and excretion of toxicants. In: Klaassen CD, Watkins JB III (eds) Casarett & Doull’s essentials of toxicology, 3rd edn. McGraw-Hill, New York, pp 61–78 Google Scholar
• Parkinson A, Ogilvie BW, Buckley DB, Kazmi F, Czerwinski M, Parkinson O (2015) Biotransformation of xenobiotics. In: Klaassen CD, Watkins JB III (eds) Casarett & Doull’s essentials of toxicology, 3rd edn. McGraw-Hill, New York, pp 79–108 Google Scholar

Author information

Authors and Affiliations

1. Former Chief of the Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar, Director of the Toxicology Consulting Group; President of the Academy of Sciences for Animal Welfare, Bareilly, India P K Gupta

1. P K Gupta