Blood brain barrier

Blood brain barrier, also known as BBB, is a term used to describe the particular properties of the central nervous system (CNS) vasculature. The vessels of the CNS do not present pores in the endothelial cells (non-fenestrated) and they contain a number of properties that tightly regulate the exchange of molecules, ions and cells. All these properties make the vessels in the CNS very restrictive and hence, it becomes an obstacle for drug delivery into the CNS.²

In the predicted ADMET features found in DrugBank, the blood brain barrier determination is produced using the prediction software admetSAR ¹ and the terms found in the table on the drug card should be considered as follows:

Value - it can be presented by  " + " or " - " indicating a yes or no relationship for the predicted property.
Probability - it presents a number between 0-1 and it indicates the certainty of the value describing the ADMET property of this drug based on the prediction software. 

For example, "There is a 67.04% probability that the drug X is able to cross the brain blood barrier based on the prediction of admetSAR software."