Because I’ve blogged about drugs lately, it’s a good time to mention the Blood Brain Barrier. If we swallow a pill, it is digested and enters the blood stream. The drug passes from our blood into all tissues, but not necessarily into the brain. This is because of a special barrier, the Blood Brain Barrier, which is fairly selective about what can and cannot reach brain tissue. The barrier is actually made up of tightly packed brain connective tissue called astrocytes that surround the blood vessels.
The good news is that the BBB acts very effectively to protect the brain from common bacterial infections. The bad news is that when brain infections do occur, the BBB may block drugs meant to fight the infecting agent. In addition, this barrier makes it more difficult to deliver wanted drugs to specific brain regions. This is especially problematic when treating brain tumors with chemotherapy. There are various chemical ways of temporarily opening the BBB to enhance drug delivery. Also, since the brain actively takes up glucose and other molecules, some drugs have been attached to these molecules to enhance their delivery. Finally, small tubes can be placed into tumor beds and attached to reservoirs that have been implanted just under the scalp so that drugs can be injected directly into the desired location.
It is hoped that nanotechnology will also provide innovative methods for delivering drugs to the targeted areas.