The BBB is responsible for physiologically protecting the brain from exposure to toxins and ill effects. However, this physiological protective function of the BBB presents a key challenge to the pharmaceutical fraternity, with a need to circumvent it to deliver drugs to the brain in various CNS disorders. While actual or potential routes across the BBB are under rigorous control to maintain the homeostatic functions of the barrier, many of them are altered or disturbed in pathology. Learn more: in vitro models of the blood brain barrier