The development of new drugs and drug vectors must also contend with potential pathological conditions of the patient. Several disease states result in enhanced BBB permeability to fluid and / or solutes (Banks and Kastin, 1996), including hypertension, radioactive exposure, edema, inflammation, ischemia, and reperfusion (reoxygenation). The list of factors that may contribute to changes in drug bioavailability (changes in BBB, protein binding, receptor site, enzymes, etc.) during a pathologic state is extensive and must be taken into account for appropriate drug design. Specific changes at the BBB, such as opening of tight junctions, increased pinocytosis, decrease in membrane rigidity, changes in nutrient transport, and pore formation may enhance/reduce drug uptake. Table 2 lists several potential conditions and factors shown to induce changes at the BBB.