Publication Ref No.: IJPRD/2011/PUB/ARTI/VOV-3/ISSUE-1/MARCH/004 ISSN 0974 – 9446          www.ijprd.com 34 DRUG TARGETING TO BRAIN : A REVIEW Daljeet Sharma 1* , Narendra Nager1, Ravindra Pal Sing 1 ,Ashish Kumar Sharma 1 1 Department Of Pharmacy Suresh Gyan Vihar University; Jaipur Rajasthan, India Email : daljeetsharma@ymail.com ABSTRACT The challenge in drug targeting is not only the targeting of drug to a specific site but also retaining it for the desired duration to elicit pharmacological action. For a nanosystem administered intravenously, the first and foremost barrier is that of the vascular endothelium and the basement membrane. Also, plasma proteins have the \ability to affect the biodistribution of drug carrier systems introduced in the blood stream. The in vivo biodistribution and opsonization of nanosystems in blood circulation is governed by their size and surface characteristics. For the nanosystem to remain in blood circulation for a long time, the major problem is to avoid its opsonization and subsequent uptake by the phagocytic cells. The tight endothelial cells in brain constitute the blood brain barrier (BBB), which restricts the entry of most drugs and delivery systems. However vascular endothelium is not uniform throughout. Another barrier is that of the extracellular matrix, which should be crossed to access the target cells in a tissue. If the whole tissue constitutes a target then the uniform distribution of drug throughout the tissue is another problem. Key Words: BBB,Biodistribution,nanoparticals,brain,nanosystem. INTRODUCTION The blood-brain barrier (BBB) is a membranic structure in the central nervous system (CNS) that restricts the passage of various chemical substances and microscopic objects (e.g. bacteria) between the bloodstream and the neural tissue itself, This "barrier" results from the selectivity of the tight junctions between endothelial cells in CNS vessels that restricts the passage of solutes. At the interface between blood and brain, endothelial cells and associated astrocytes are stitched together by structures called tight junctions. The tight junction is composed of smaller subunits, Daljeet Sharma