In Vivo Testing

Simply stated, in vivo testing is the testing of an investigational drug or device in a living system. This is in contrast to in vitro testing, in which the testing is carried out in a “test tube” (nonliving) system. One way to learn how a drug or device may affect people is to understand their effects in appropriate animal models. In vivo testing systems may include specific genetic animal models. These specific models may be used to evaluate neoplastic (cancer), neurologic, cardiovascular, immune, metabolic, infectious, and endocrine diseases.

Unlike in vitro analysis, in vivo testing requires that the drug or device be able to overcome barriers between the initial location (perhaps an intravenous injection) and the target. These barriers may include vascular endothelium, basement membranes, cell membranes, and intracellular organelle membranes. Pharmacokinetic effects may also have an important role in an in vivo system. The absorption, distribution, metabolism, and excretion of a drug can dramatically affect how it interacts with the target organ or receptor–effector system. In vivo testing can help establish the most effective routes of administration as well as side effects and toxicities that cannot be directly evaluated in vitro. In vivo testing is regulated by the U.S. Food and Drug Administration (FDA), and approval for research in animals must be sought. An institutional review board (IRB) must approve the study, and good clinical practices (GCPs) in accord with the FDA and the International Conference on Harmonization (ICH) must be followed.