Oral Bioavailability
Definition
Bioavailability by mouth, which for most peptides is under 1%: gastric acid and intestinal proteases degrade them and the surviving fraction struggles to cross the epithelium. Overcoming it takes permeation enhancers, enteric protection or a very short sequence.
What this means for research sourcing
Mechanistic terms like this describe how research compounds behave in vitro. See the mechanism overviews for compounds Volta stocks.
Related Terms in Pharmacology
Half-Life
The time taken for the amount in the body to fall by half. It sets how often a compound has to be given and how long elimination takes, about four to five half-lives for the bulk of it to clear.
Clearance
The rate at which the body removes a compound from blood, through the kidneys, the liver, or enzymatic breakdown in plasma. Clearance together with volume of distribution is what produces the half-life, rather than the other way round.
Steady State
The point in repeated administration where the amount going in matches the amount being cleared, so peaks and troughs stop climbing. It takes roughly four to five half-lives to arrive, whatever the interval.
Area Under the Curve (AUC)
Total exposure over time, the integral of plasma concentration against time. Two regimens can share a peak concentration and differ substantially in AUC, which is why trials report both.
Pharmacokinetics
What the body does to a compound: absorption, distribution, metabolism and excretion. Half-life, peak concentration and dosing interval all come out of pharmacokinetic work.
Pharmacodynamics
What a compound does to the body: the link between concentration at the target and the size of the resulting effect. It is the counterpart to pharmacokinetics and the two are routinely modelled together.
First-Pass Metabolism
The breakdown a swallowed compound undergoes in the gut wall and the liver before it reaches general circulation. It is a principal reason peptide drug development has concentrated on injected routes.
Enzymatic Degradation
Cleavage of a peptide by proteases in blood and tissue, which cut at sequence-specific points. Designing around it, by substituting a residue, cyclising the chain or capping a terminus, is the central problem in making a natural peptide usable as a drug.