Definition
Research performed in a whole living organism, such as rodent models or human clinical trials.
In vivo, Latin for "within the living", describes studies performed in whole organisms. In peptide research this usually means animal models, most often mice and rats, and later human clinical trials. In vivo studies capture absorption, distribution, metabolism, elimination and interactions between organ systems that in vitro work cannot. They require institutional ethical approval, such as an animal care and use committee in the US, and careful control of variables such as species, strain, sex and vehicle. Results in rodents frequently fail to translate to humans, which is why preclinical in vivo findings are treated as hypothesis-generating rather than conclusive.