What is Bioavailability?

Bioavailability is a measurement of the rate and extent (amount) to which the active ingredient or active moiety becomes available at the site of action; it is also considered a measure of the rate and extent of therapeutically active drug that is systemically absorbed. For products not intended for the bloodstream, bioavailability may be assessed by measurements that reflect availability at the site of action.

Two words carry the whole chapter: RATE (how fast) and EXTENT (how much). Bioavailability asks both about a single product. Bioequivalence then asks whether TWO products match on rate and extent.

📖 “Bioavailability = rate and extent to which the active moiety becomes available at the site of action / is systemically absorbed.”