In addition to protein availability, other factors can affect drug absorption and distribution in the body as a whole or more narrowly within specific sites of the body. Table 2 highlights some of these other factors.
Table 2. Other Factors Affecting Drug Absorption and Distribution.| Factor | Discussion |
| Regional blood flow | Reduced blood flow to an organ can be seen in diabetics, and enhanced blood flow can be seen in tumors. Reduced blood flow means reduced exposure to drug.
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| 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 and there also exists a tighter-than-normal web of epithelial cells in the blood vessels of the CNS. This leads to the so-called blood-brain barrier. Lipophilic drugs can cross cell membranes of this barrier more easily than polar drugs. |
| 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, the metabolism of drugs is reduced in the elderly. |
| Genetics | Mutations or deletions in drug-metabolizing enzymes can greatly affect a drug's disposition. |
