xen·o·bi·ot·ic (z n  -b - t  k, z n-)adj. Foreign to the body or to living organisms. Used of chemical compounds. n. A xenobiotic chemical. |
xenobiotic
[-bī·ot′ik]
Etymology: Gk, xenos, strange, bios, life
a chemical compound foreign to a given biologic system. With respect to animals and humans, xenobiotics include drugs, drug metabolites, and environmental compounds, such as pollutants that are not produced by the body. In the environment, xenobiotics include synthetic pesticides, herbicides, and industrial pollutants that would not be found in nature.
xenobiotic
any substance, harmful or not, that is foreign to the animal's biological system.
xenobiotic transformation
the principal mechanism for maintaining homeostasis during exposure to small foreign molecules such as drugs and toxins; the process deals with foreign chemicals which are too small for processing by the immune system; composed of enzyme systems evolved to render xenobiotics easily excreted, mainly in the liver; enzymic reactions classified as Phase I (add to or expose functional chemical groups; includes cytochrome P-450 monooxygenases) and Phase II (glucuronidation, conjugation and other reactions producing a large increase in water solubility to promote excretion). Cats lack the capacity for glucuronidation, making them more susceptible to certain poisonings, e.g. acetaminophen (paracetamol).
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