Drug resistance in epilepsy: the role of the blood-brain barrier.

The blood-brain barrier (BBB) is formed by the endothelial cells lining the brain microvessels. Complex tight junctions linking adjacent endothelial cells make brain capillaries around 100 times tighter than peripheral capillaries to small hydrophilic molecules. As a result, drugs required to act in the brain, including anti-epileptic drugs (AEDs), have generally been made lipophilic, and are thus able to cross the brain endothelium via the lipid membranes.