In Vivo

Definition

In vivo (Latin: "within the living") refers to biological research conducted within living organisms, most commonly rodent models (mice and rats), but also zebrafish, C. elegans, primates, and other species depending on the research question. In vivo experiments capture the full pharmacokinetic and pharmacodynamic complexity of compound behavior in a living system, including absorption, distribution, metabolism, excretion, and the systemic response to compound administration. In vivo models provide more physiologically relevant data than in vitro systems but involve greater biological variability, higher cost, and regulatory requirements for animal research conduct.

Research Context

In vivo preclinical research is the standard for evaluating research peptides beyond initial mechanistic characterization. The majority of published research on compounds such as BPC-157, TB-500, Semax, and Thymosin Alpha-1 comes from rodent in vivo studies using standardized injury or disease models. In vivo research requires appropriate institutional animal care committee (IACUC) approval and adherence to the 3Rs principles (replacement, reduction, refinement) of ethical animal research. The validity of in vivo research depends on careful model selection, appropriate controls, blinded endpoint assessment, and statistical power calculations.