Studies that are
in vivo (
Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living
organisms usually animals including humans, and plants as opposed to a
partial or dead organism, or those done
in vitro ("within the glass"), i.e., in a laboratory environment using test tubes,
petri dishes etc. Examples of investigations
in vivo include: the pathogenesis of disease by comparing the effects of bacterial infection with the effects of purified bacterial toxins; the development of antibiotics, antiviral drugs, and new drugs generally; and new surgical procedures. Consequently,
animal testing and
clinical trials are major elements of
in vivo research.
In vivo testing is often employed over
in vitro because it is better suited for observing the overall effects of an experiment on a living subject. In
drug discovery, for example, verification of efficacy
in vivo is crucial, because
in vitro assays can sometimes yield misleading results with drug candidate molecules that are irrelevant
in vivo (e.g., because such molecules cannot reach their site of
in vivo action, for example as a result of rapid
catabolism in the liver).