Pharmaceutical Statistics Using SAS

2.2. Motivating Example

Generally speaking, permeability is the ability of a molecule to cross a membrane.In the body, key membranes exist in the intestine and brain, and are composed of layers of molecules and proteins organized in a way to prevent harmful substances from crossingwhile allowing essential substances to pass through. The intestine, for instance, allowssubstances such as nutrients to pass from the gut into the blood stream. Another membrane, the blood-brain barrier, prevents detrimental substances from crossing the blood stream into the central nervous system. While a molecule may have the correct characteristics to be effective against a specific disease or condition, it may not have the correct characteristics to pass from the ...