4. FACTORS AFFECTING DISTRIBUTION OF
DRUGS
The extent of distribution to the different tissues depends
on
drug lipophilicity,
ionization state,
plasma proteins binding, and
tissue binding.
1.
2.
3.
4.
6. Binding to Plasma Proteins
THE FREE (NON-BOUND) FRACTION OF A DRUG IS IN
EQUILIBRIUM WITH THE BOUND FRACTION; HOWEVER
ONLY THE FREE DRUG CAN FURTHER DIFFUSE.
7. Perfusion and Membrane Permeability
Diffusion rate-limited distribution can occur for drugs
with low membrane penetration ability, or in specific
tissues with low membrane permeability
8. ACCUMULATION IN ORGANS AND
TISSUES
Usually drugs are not uniformly distributed to all body
tissues.
The concentration of some drugs can be either
significantly higher or lower in specific tissues
9. Accumulation is usually a reversible equilibrium process and
as such the accumulating organ can function as a drug
reservoir.
