A--Drug A is an undissolved drug. It is not in solution and it cannot be
B--B is a molecule of a drug in solution. It is unionized and can be
C--C is a molecule of a drug attached to a "carrier molecule" at the cell
D--D is an ion of a drug. It cannot be absorbed since the fatty layer
E--E is a molecule of a drug. It is in circulation and will be carried away.
F--F is a molecule of the drug that is being released into circulation by a
Figure 3-3. Illustration of drug transport concepts.
NOTE: Passive transport or diffusion has absorbed Molecule B. Once it has been
absorbed, the circulating blood will carry it away. Consequently, the concentration of
the drug will always remain higher in the gut and diffusion will continue. As the
unionized particles are absorbed, the ionized particles will attach to each other to form
more unionized drug. This occurs because the drug has equilibrium established