Lisaji said...
Excuse my ignorance, but what is cross blood brain barrier?
The brain has a network of blood vessels surrounding it creating a protective barrier that attempts to block out harmful substances, but allow nutrients in. It often prevents drugs from being able to enter and help repair the injury or disease of the brain.
In order for substances to penetrate the b/b barrier, they have to be very small and/or fat soluble. Larger molecules have more difficulty passing through.