ABSTRACT
The extent of absorption (fa) can be defined in terms of all processes, from the dissolution of the solid dosage form to the uptake of the drug into the intestinal tissue (i.e., transport across the apical membrane of the enterocyte). This general definition for the extent of absorption does not include metabolic first-pass effects in the gut or liver or biliary excretion in the liver (Ec and EH) (1,2). The bioavailability (F) of a compound is a consequence of all these processes, as shown in Eq. (1).
