Bioavailability

Definition

Bioavailability is a pharmacokinetic measure that quantifies the proportion of a administered compound that enters the systemic circulation in unchanged, active form relative to an intravenous reference dose. For peptide compounds studied in animal models, bioavailability is highly dependent on the route of administration, the peptide sequence, molecular weight, and susceptibility to enzymatic degradation in the gastrointestinal tract or at injection sites. Oral bioavailability for most unmodified peptides is very low due to proteolytic degradation before absorption. Subcutaneous and intraperitoneal routes are commonly used in preclinical research to achieve higher systemic exposure.

Research Context

Bioavailability is a central consideration in preclinical peptide research design because it determines what fraction of the administered dose actually reaches target tissues. Peptides such as BPC-157 and TB-500 have been studied primarily via subcutaneous or intraperitoneal routes in preclinical models, where bioavailability is substantially higher than oral routes. Chemical modifications such as PEGylation or acylation are studied as strategies to improve bioavailability and extend compound half-life.