Nose to brain drug delivery through advanced drug delivery systems

The selective semipermeable cerebral microvasculature, popularly known as the blood-brain barrier (BBB) protects the brain from circulating xenobiotics, microorganisms, and other toxins. BBB, however, forms a formidable barrier to the entry of drug molecules into the brain despite their systemic availability. This, in turn, necessitates the use of highly invasive drug delivery routes like intra-arterial injection into intracranial vessels or intrathecal injections. The nasal delivery route, on the other hand, offers a relatively non-invasive route that bypasses the blood-brain barrier. Several formulation strategies have been reported with varying degree of success for a plethora of drug molecules. The review not only discusses the success achieved hitherto but also delves deeper into indicating the factors that are accountable for the success or failure of the delivery systems.