In addition to protein availability, other factors may affect drug absorption and distribution in the body as a whole or within specific sites of the body. The following table highlights some of these other factors.
|Regional blood flow||Reduced area blood flow can be seen in diabetics and enhanced blood flow can be seen in tumors. Reduced blood flow means reduced exposure to drug.|
Lipid solubility of the drug
|The more lipophilic a drug is, the more likely it will enter the central nervous system. The brain itself is a very lipid-rich organ but there also exists a tighter-than normal web of epithelial cells in the CNS blood vessels. This leads to the so called blood-brain-barrier. Lipophilic drugs can cross cell membranes of this barrier more easily than polar drugs. |
|The integrity of the GI tract||In a diseased gut, an orally-administered drug may not be absorbed as expected.|
|Age||Drug kinetics and dispositions change throughout life. In general, metabolism of drugs is reduced in the elderly. |
|Genetics||Mutations or deletions in drug metabolizing enzymes can greatly affect a drug's disposition. |