
Physiological aspects on pharmacokinetics 93
a change in formulation or manufacture process requires an investigation of
the absorption process in a bioequivalence study.
The process that leads to a solid drug formulation being absorbed into the
blood stream has two distinct steps:
solid drug −→ drug in solution −→ absorbed drug.
Note that any of these two steps can be rate-limiting. If it is the second step
that is rate-limiting, there will be more drug in solution in the intestines than
if it is the dissolution that is rate-limiting. The mean absorption time, as
defined earlier, is the time it takes from the drug is swallowed until it appears
in plasma, ...