Body and drug basics
Bioavailability
Last updated
Bioavailability is the share of a substance that actually reaches the bloodstream in a usable form. Injection straight into a vein is the reference point and counts as complete, because nothing is lost on the way. Everything else, including anything swallowed, is compared against that and reported as a percentage.
Why it matters here
It is the main reason the route of administration matters so much, and the reason many peptides are not taken by mouth: the digestive system takes chains of amino acids apart much as it takes the protein in food apart. Two products containing the same substance can differ enormously on this figure.
What it is not
Not the same as absorption. Something can be absorbed out of the gut perfectly well and still be largely dismantled by the liver before it reaches general circulation, so bioavailability can be far lower than the amount taken up. It also says nothing about whether the share that arrives does anything.
Also called
- bioavailability
- bioavailable
- oral bioavailability
- absolute bioavailability
- relative bioavailability
- systemic availability
Abbreviated F in pharmacology papers. Absolute bioavailability is the comparison against injection into a vein; relative bioavailability compares two other routes with each other.
Compounds carrying this term
None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.