In Vivo

In Vivo designates biological processes, experiments, or therapeutic effects occurring within intact living organisms, providing comprehensive physiological context including complex organ interactions, immune responses, metabolic pathways, and systemic regulation impossible to fully replicate through in vitro systems. This fundamental research approach employs animal models and clinical studies in humans representing ultimate in vivo validation.

The pharmaceutical industry conducts extensive in vivo studies throughout preclinical and clinical development. Pharmacokinetic studies measure drug absorption, distribution, metabolism, and elimination in living systems, informing dosing strategies. Efficacy assessment employs disease models evaluating therapeutic effects on pathophysiology, survival, or disease markers. Toxicology studies identify potential adverse effects examining multiple organ systems. Regulatory requirements mandate in vivo safety studies before human trials. The 3Rs principles promote replacement, reduction, and refinement of animal studies. As in vitro and computational methods improve, animal use declines for applications where alternatives prove adequate, though complex whole-organism questions remain requiring in vivo approaches.